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Notes: Abstract A retrospective study was made of the clinical data in 118 dogs and 17 cats with thrombocytosis. The mean platelet count for dogs was 647 × 109/l and for cats was 767 × 109/l. There was no significant difference in platelet count based on species, age or sex. The most common disease categories associated with thrombocytosis were neoplasia (25%), gastrointestinal disorders (19%) and endocrine disorders (10%). The most common drug classes associated with thrombocytosis were corticosteroids and antineoplastic agents.

Notes: Summary A new method of external selective brain cooling is described, showing its effectiveness in reducing neuronal damage following global cerebral ischemia in cat. The cooling apparatus consists of a specially fitted kind of water jacket in which the animal's head was laid. In a preliminary study it was verified that the device effectively reduces brain temperature without the risk of cardiac arrhythmias due to lowering of core temperature. In the main study cardiac arrest was induced in 23 adult cats, followed after 15 min by cardiopulmonary resuscitation (CPR). Eight cats could not be revived; of the 15 remaining animals, 7 were assigned to the control group (normothermia) and 8 to the treatment group (cerebral hypothermia). The latter received external brain cooling for 30 min, starting as soon as CPR was begun. Four hours after cardiac arrest all animals were transcardiacally perfused with glutardialdehyde. The brains were stored in fixative and subsequently processed for histopathological and morphometrical evaluation by light microscopy. Analysis of the resulting data showed that animals in the treatment group had a significantly higher percentage of undamaged neurons than animals in the control group, both in the cingulate gyrus (38% vs 10%) and in the parietal cortex (39% vs 14%). The treatment group also had more undamaged neurons in the hippocampus and fewer severely damaged neurons in all three regions, but these differences, though suggestive, were not statistically significant.

Notes: Summary The brainstem projections of the ampullar nerves from the vertical semicircular canals, the anterio (AAN) and the posterior ampullar nerve (PAN), were studied in adult cats using the transganglionic horseradish peroxidase (HRP) method. Each nerve was exposed in three experiments. Two animals in each group had labeling which allowed detailed mapping. From the AAN, terminal-type labeling was found in two separate groups, one laterally and one medially, both in the lateral (LV) and in the superior (SV) vestibular nucleus. In addition, such labeling was found in all parts of the medial vestibular nucleus (MV). Labeled structures were found also in the descending vestibular nucleus, (DV) more densely over its lateral part, except for cell group f, where no labeling was found. From the PAN, terminal-type labeling was found medially and laterally in the LV and in the medial part of the SV In the MV, such labeling was evenly distributed rostrally but concentrated laterally in caudal parts. In the DV, terminal-type labeling was present rostrally, whereas no labeling was seen caudally. In the interstitial nucleus of the vestibular nerve, terminal-type labeling was observed from the AAN but not from the PAN. No labeled fibers from either of the two ampullar nerves were seen outside the vestibular root and nuclei, except for small-caliber fibers from the SV heading towards the brachium conjunctivum. The findings clearly indicate a specific termination for each of the two ampullar nerves.

Notes: Summary The arterial and venous systems of the neck and heads of a dicephalic iniodymic monosomic cat are described. In the arterial system, an anomalous lingual branch of the right external carotid formed a large subhyoid arch, extending to the midline between both heads, giving off branches supplying the medial aspect of both heads and terminating in two medial internal carotid arteries each for the right or left head. This vessel was considered as an anomalous supernumerary common carotid artery. In the venous system, each lingual branch of linguofacial veins united and formed an anomalous venous arch. It received rostrally a long midline vein running between both heads and connecting with the medial internal jugular system. This vein received tributaries from the left and right heads and was considered as a supernumerary jugular vein. From these observations, and those of others in the literature, it can tentatively be suggested that, in congenital cephalic duplications in domestic mammals, the arterial blood supply for the medial aspect of both heads tends to come from the lingual branch of the external carotid artery, with an unexplained prevailing contribution of the right external carotid system. Two different venous patterns have been observed. In animal especies exhibiting a hyoid venous arch, such as carnivores, a midline supernumerary external jugular vein draining at the anomalous junction between lingual veins of both heads is formed, whilst in animals lacking a constant hyoid venous arch, such as ruminants, an asymmetrical supernumerary external jugular vein draining into the right “normal” external jugular vein has been repeatedly described.

Notes: Summary Three female cats, littermates born from clinically normal parents, were examined at 8 to 10 weeks of age because of a slowly progressive posterior ataxia. Another cat from a previous litter from the same parents suffered from similar neurological symptoms. Histopathological examination of the nervous tissues of these animals revealed degeneration of axons and myelinopathy in a distal distribution pattern. Both peripheral nerves and central nervous system were involved. The central nervous system lesions were most prominent in the lateral pyramidal tracts of the spinal cord, the fasciculi gracili of the dorsal column in the cervical spinal cord and the cerebellar vermian white matter. In the PNS numerous degenerating nerve fibers were found in the sciatic nerves but not in the spinal nerve roots. Our findings show that these cats were suffering from a hereditary multisystem degeneration with a distribution pattern of the lesions suggestive of a distal axonopathy.

Notes: Summary Simple (N = 284) and complex cells (N = 125) in the central projection area (0–5° eccentricity) of the striate cortex of cats were stimulated with moving light bars and the responses to different directions of movement were recorded and plotted as polar-plots. Fourier analysis was applied to polar plots (SDO-analysis, Wörgötter and Eysel 1987; Wörgötter et al. 1990) to determine the general sensitivity (S) of the cells to visual stimulation, the directional (D) and orientational (O) tuning strength as well as preferred direction (PD) and preferred orientation (PO). Statistical distributions of the S, D and O parameters were determined for simple and complex cells of the cortical layers II–VI. Simple cells were more strongly tuned for direction and orientation than complex cells, whereas complex cells had a greater general sensitivity to visual stimulation. Directional tuning was significantly stronger in layer VI than in layer IV simple cells, otherwise no differences were detected between these two layers. We found that cells with large D and small O components are generally rare. The D and O components were plotted against each other to determine any possible correlation between the tuning strengths. The correlations were statistically significant for simple and complex cells but the correlation coefficients were very small (r 〈 0.3). It is suggested that only a very weak coupling between directional and orientational tuning exists, preferentially in the deeper layer simple cells.

Notes: Summary In ten cats, single unit electrical activity was recorded in the lumbosacral spinal cord from neurones driven by stimulation of afferent fibres from the ipsilateral knee joint. Tonic descending inhibition (TDI) on the responses of these cells was measured as increases in resting and evoked activity of the neurones following reversible spinalization of the animals with a cold block at upper lumbar level. Acute inflammation of the knee joint was induced in five of the cats by the injection of kaolin and carrageenan into the joint. TDI was observed in 25 of 33 neurones recorded in normal animals (76%) and in 36 of 40 (90%) neurones recorded in animals with acute knee joint inflammation. In both kinds of preparation TDI was more pronounced in neurones recorded in the deep dorsal horn and in the ventral horn than in those recorded in the superficial dorsal horn. There was a tendency in the whole sample for TDI to be greater in neurones with input from inflamed knees. We conclude that the spinal processing of afferent information from joints is under tonic descending influences and that the amount of TDI can be altered during acute arthritis.

Notes: Summary Seventy-one (n = 71) premotor interneurones have been localized by extracellular recordings within the subnucleus-γ of the oral nucleus of the spinal trigeminal tract (NVspo-γ) in nineteen chloralose anaesthetized cats. The neurons were antidromically activated by microstimulation (minimum = 3μA) applied to the digastric motoneurone subnucleus of the trigeminal motor nucleus. Fifty-one (n = 51) of the interneurones were discharged from the ipsiand nineteen (n = 19) from the contralateral digastric subnucleus. One neurone out of four tested was antidromically activated from both stimulation sites suggesting a bifurcated axon. The identified premotor neurones had a unique convergence profile of oral and perioral primary afferents. Latency calculations indicated that at least 55% of these interneurones were monosynaptically activated by low stimulus strength applied to the inferior alveolar (minimum=1.0 T) and/or the lingual nerve (minimum=1.0 T). The thresholds for evoking the neuronal discharges coincided statistically with those required to evoke a jaw opening reflex response by stimulation of the same nerves. It is suggested that the specific group of NVspo-γ interneurones under different contexts mediates the disynaptic reflex and participates in the centrally and reflexly evoked “patterning” adjustments of the digastric jaw opening motoneurones during ongoing jaw movements. A companion paper reports the convergence of descending cortical, tectal and ascending cervical inputs, as well as of oro-facial and neck primary afferent inputs onto an unselected population of interneurones in the NVspo-γ (Westberg and Olsson 1991).

Notes: Summary The aim of this study was to corroborate lesioning work (Mackel and Noda 1989), suggesting the pretectal area of the rostral midbrain acts as a relay between the spinal cord and the ventrolateral (VL) nucleus of the thalamus. For this purpose, extracellular recordings were made from neurons in the pretectal area which were antidromically activated by stimulation in the rostral thalamus, particularly in VL. The neurons were tested for input from the dorsal columns of the spinal cord, the dorsal column nuclei, and the ventral quadrant of the spinal cord. Latencies of the antidromic responses ranged between 0.6 and 3.0 ms (median 1.0 ms): no differences in latencies were associated with either location of the neurons in the pretectal area or with the site of their thalamic projection. Orthodromic responses to stimulation of ascending pathways were seen in the majority of neurons throughout the pretectal area sampled. Latencies of orthodromic responses varied considerably, with ranges of 0.9–9 ms, 6–20 ms, and 2.5–20 ms upon stimulating the dorsal column nuclei, dorsal columns, and ventrolateral quadrant, respectively. The shortest-latency responses to stimulation of the dorsal column nuclei or of the ventral quadrant were likely to be monosynaptic. Temporal and spatial facilitation of the responses to ascending input were common. The data show that neurons of the pretectal area are capable of relaying somatosensory input ascending from the spinal cord to the rostral thalamus. It is suggested that the pretectofugal output to VL converges with cerebellar input in VL neurons and becomes incorporated in cerebello-cerebral interactions and, ultimately, the control of movement.

Notes: Summary The qualitative and quantitative synaptology of flat synaptic vesicle containing “F” type terminals was analysed in normal and in chronically cortically deafferented dorsal Lateral Geniculate Nucleus (dLGN) of the cat using an electron microscopic immunogold technique for visualization of GABA. A direct correlation was found between the density (number of gold particles) of GABA immunostaining and the number of synaptic vesicles in different F terminals. This suggested a quantitative relationship between transmitter content and the number of vesicles in the labeled terminals. Not only the number but also the size of synaptic vesicles was found to be different in the two main groups of F profiles, i.e. the axonal F1 and dendritic F2 terminals. Measurement of the size of synaptic vesicles in F1 axon terminals revealed two subpopulations of these endings: “F11” and “F12” terminals with vesicle diameters of 31.56 ± 0.08 nm and 33.73 ± 0.12 nm (P 〈 0.01; Chi2 test) respectively. The size of synaptic vesicles in axonal F12 terminals was identical to that found in F2 dendritic profiles, suggesting that both processes belonged to the same, intrageniculate (interneuronal) cell population. F11 terminals, however, appeared to be axonal endings of extrageniculate (most probably of perigeniculate) neurons. Quantitative analysis of the two types of GABAergic axon terminals revealed the geniculocortical relay cells to be the main postsynaptic targets for F11 (extrageniculate) terminals while F12 axons terminated equally on both interneurons and relay cells. Following chronic decortication of the dLGN, the distribution pattern of both GABAergic axonal types had changed considerably. As a result of a severe loss in relay cells, more F11 and F12 axon terminals were found on GABA-containing interneuronal processes than on relay cells. An increase in the number of F1 axonal terminals per neuron was also revealed, (particularly on GABAergic interneurons), suggesting a compensatory reactive synaptogenesis by both F axonal types following decortication.

Notes: Summary The goal of this study was to assess changes in synaptic activity in the visual cortex of kittens following brief periods of monocular deprivation. Field potentials evoked by electrical stimulation of both optic nerves were registered in vertical penetrations through areas 17 and 18 of 4–5 week-old kittens which had been monocularly deprived for 2–7 days. In order to assess the laminar distribution of synaptic currents these field potentials were subjected to a current source density analysis. Current source density profiles elicited from the deprived eye differed from those induced from the normal eye in several respects: 1) The amplitudes of the responses showed considerable variation at different recording sites across the tangential dimension of cortex. 2) On the average, sinks and sources were markedly reduced, and this reduction was relatively more pronounced in nongranular than in granular layers. 3) However, in 30% of the tracks the layer IV sink showed no attenuation. It was reduced in 48% of the tracks and completely suppressed in 22% of the tracks. These results indicate that a substantial fraction of the deprived thalamocortical synapses remained functional, but that many of these synaptic events remained subthreshold. The significance of these findings is discussed in the context of recovery processes following reverse suture.

Notes: Summary Analysis of published values for the depth profile of evoked potentials in primary sensory cortex of cat and monkey provide a consistent estimate for the net current dipole moment per unit area of cortical surface. Comparison with values of the total current dipole moment obtained from neuromagnetic studies on human subjects indicates that coherent neuronal activity giving rise to long-latency sensory evoked components recorded in the human electroencephalogram or magnetoencephalogram extends over a cortical area that is typically ∼40–400 mm2.

Notes: Summary Electroencephalogram, caudate nucleus temperature (Tc), ear skin temperature (Te) as well as cerebral blood flow (CBF) measured by a thermal clearance method, were recorded simultaneously and continuously in cats. After baseline recording in which we confirmed the increase of Tc during paradoxical sleep (PS), neuronal cell bodies of the mesencephalic reticular formation and/or the posterior hypothalamus (PH) were destroyed with ibotenic acid. Only PH lesions were followed by either a suppression of the increase or even a decrease of Tc during PS while Te variations were not modified. The decrease in CBF, which was always associated with Tc increase, was suppressed after the PH lesion. These results led us to the conclusion that the increase of Tc at the onset of PS is due to a decrease in CBF. Furthermore, it may be hypothetized that the decrease in CBF depend upon an active vasoconstriction process originating in the PH.

Notes: Summary The cat sartorius (SA) can be divided functionally into an anterior (SAa), knee extensor portion and a medial (SAm), knee flexor portion; it can be further subdivided anatomically by multiple nerve branches into parallel longitudinal columns that terminate in a distributed insertion at the knee with a continuous range of moment arms. Thus, SA may be controlled by a discrete number of motoneuron task groups reflecting a small number of central command signals or by a continuum of activation patterns associated with a continuum of moment arms. To resolve this question, the activation patterns across the width of the SA were recorded with an electrode array during three kinematically different movements — treadmill locomotion, scratching and paw shaking, in awake, unrestrained cats. Uniformity of activation along the longitudinal axis was also examined because individual muscle fibers do not extend the length of the SA. In addition, the cutaneous reflex responses were recorded throughout all regions of the SA during locomotion. Two fascial surface-patch arrays, each carrying 4–8 pairs of bipolar EMG electrodes, were sutured to the inner surface of the SA, one placed proximally and the other more distally. Each array sampled separate sites across the anterior to medial axis of SA. During locomotion, two basic EMG patterns were observed: the two burst-per-step-cycle pattern typical of SAa and the single burst pattern typical of SAm. There was an abrupt transition in the pattern of activation recorded in the two parts of SA during locomotion, and no continuum in the activation pattern was observed. Stimulation of both sural and saphenous cutaneous nerves during locomotion produced reflex responses that were uniformly distributed throughout SA, in contrast to the regional differences noted during unperturbed walking. Similarly, during scratching and paw shaking all parts of the SA were active simultaneously but with regional differences in EMG amplitude. The abrupt functional border between SAa and SAm coincided with the division of the SA into a knee flexor vs. a knee extensor. In all cases, the quantitative and qualitative differences in SAa and SAm EMGs were uniformly recorded throughout the entire extent of SAa or SAm; i.e., there was no segregation of activity within either SAa or SAm. Furthermore, the time course of EMG from each proximal recording site was nearly identical to the corresponding distal site, indicating no segregation of function along the longitudinal axis of SA. These results indicate that SAa and SAm constitute the smallest functional modules that can be recruited in SA. The functional subdivision of the SA motor nucleus is reflected in the central pattern generators for these movements to permit a task-dependent recruitment of any combination of SAa and SAm. Our data indicate that the number of task groups even in an anatomically and functionally complex muscle like the SA is small and appears to be related to the kinematic conditions under which the muscle operates.

Notes: Summary Several cat hindlimb muscles that exhibit differential activation (activity that is restricted to a specific region of muscle) during natural movements were studied to determine the possible roles of 1) non-uniform distribution of histochemically-identified muscle fiber-types (semitendinosus, ST; tibialis anterior, TA) or 2) mechanical heterogeneity (biceps femoris, BF; tensor fasciae latae, TFL). Using chronic recording techniques, electromyographic (EMG) activity was recorded from multiple sites of each muscle during treadmill locomotion, ear scratch, and paw shake. Standard histochemical analysis was performed on each muscle to determine fiber-type distribution. The histochemically regionalized muscles (ST and TA) were differentially active during slow locomotion; the deep regions (high in type I [SO] fibers) were active, but the superficial regions (high in type IIB [FG] fibers) were inactive. Vigorous movements (fast locomotion, ear scratch, paw shake) produced additional, synchronous activation of the superficial regions. In all movements, ST and TA activation patterns were consistent with the existence of identically timed synaptic inputs to all motoneurons within each motoneuron pool, resulting in an orderly recruitment of each whole pool. The differential activation recorded from ST and TA during slow locomotion was presumably a consequence of the non-uniform distribution of the different muscle fiber types. In contrast, differential activation of the histochemically nonregionalized, mechanically heterogeneous muscles (BF and TFL) resulted from non-synchronous activation of different muscle regions. The selective activation of BF or TFL compartments was indicative of differential synaptic inputs to, and selective recruitment of, subpopulations of the motoneuron pool, with each motoneuron subpopulation exclusively innervating physically separate regions of the muscle consistent with the regions defined by the neuromuscular territories of the major nerve branches supplying each muscle. Individual neuromuscular compartments of BF and TFL differ in their mechanical arrangements to the skeleton and in their contribution to mechanical action(s) at the hip and knee joints. Selective neural activation of mechanically distinct compartments within a mechanically heterogeneous muscle can provide highly advantageous mechanical “options” for animals that perform kinematically diverse movements. With regard to EMG recording techniques, the results of this study emphasize the need for carefully chosen EMG sampling sites and the value of knowing the muscle histochemistry, neuromuscular and musculoskeletal anatomy and possible mechanical functions prior to recording EMG.

Notes: Summary The purpose of this study was to examine the effect of bilateral labyrinthectomy on quiet stance in the freely-standing cat. Since loss of the vestibular end organs produces marked deficits in motor behaviour, including ataxia and problems with balance, we hypothesized that labyrinthectomized animals would show impairment in quantitative measures of stance. Stance was quantified in terms of the ground reaction forces under each limb and the tonic electromyographic (EMG) activity of selected muscles. Animals were labyrinthectomized by drilling into the vestibule and removing the vestibular epithelium. Following lesion, animals were able to stand unsupported on the force platform within 2 days. To our surprise, the lesioned animals showed little change in stance parameters from the control, pre-lesion state. Thus, our hypothesis of changes in stance parameters was not supported. There was no change in the distribution of vertical forces under the limbs and no increase in sway, as measured by the area of excursion of the centre of pressure over time. The horizontal plane forces, which were diagonally directed prior to lesion, became more laterally directed and larger in amplitude. The change in direction persisted even after the animals had fully compensated for the lesion, but the force amplitudes returned to control values within 10–12 days. The change in horizontal force direction was similar to that observed in normal animals that were required to stand with their paws closer than preferred in the sagittal plane (unpublished observations). EMG activity changed in some muscles but not others, and usually transiently. One limb extensor showed decreases in tonic activity (gluteus medius), but other extensors showed increases (vastus medialis, soleus). It is likely that the changes in EMG levels were due to the biomechanics of the stance configuration related to the changes in direction of the horizontal plane forces. Kinematic recordings are needed to address this issue further.

Notes: Summary The technique of antidromic mapping with a roving array of electrodes was used to demonstrate that lamina I trigeminothalamic cells responsive specifically to skin temperature project to the n. submedius (Sm) in the medial thalamus of the cat. This finding indicates that Sm receives thermoreceptive in addition to nociceptive information.

Notes: Summary Prior studies of thalamic neurons have demonstrated that they exhibit at least two response modes: a relay mode and a burst mode. During the relay mode, sensory information is faithfully relayed to cortex; during the burst mode, which is caused by a voltagedependent Ca2+ conductance, this relay of sensory information is interrupted. We began in vivo studies of these response modes in neurons from the lateral geniculate nucleus of anesthetized, paralyzed cats. Each of the 9 X and 10 Y cells we recorded intracellularly displayed voltage-dependent, low threshold spikes that were presumably the Ca2+ spikes described from in vitro recording. These spikes were triangular in waveform and typically had 2–7 fast action potentials (interspike intervals of 1.2–4 ms) riding its crest. Furthermore, the cell's membrane had to be hyperpolarized to de-inactivate the low threshold spike before a depolarization could then activate it. We could activate these low threshold spikes in Y cells from EPSPs, whether spontaneous or evoked from activation of the optic chiasm. However, in only one of the X cells could we activate low threshold spikes from chiasm shock; in the remainder, we could activate low threshold spikes only via depolarizing current pulses, possibly because the EPSPs of these X cells were too small to activate these spikes. We also used extracellular recording to study spontaneous activity and responses to chiasm shock from 114 geniculate neurons and, as a control, 57 optic tract axons. We concentrated on periods of bursty responsiveness signifying the burst mode. We define a burst as 2–7 action potentials with interspike intervals 〈= 4 ms, and the bursts are separated by 〉 100 ms; from our intracellular recording, we know that such bursts signify low threshold spikes. We found that, during extracellular recording, 20 of the 39 X cells and each of the 75 Y cells displayed evidence of the burst response mode, although burst periods were rare in X cells. Electrical activation of the optic chiasm greatly enhanced the burstiness of Y cells for periods of 500 ms or more. We also electrically stimulated the parabrachial region of the midbrain, which provides a mostly cholinergic innervation to the lateral geniculate nucleus. Although parabrachial activation by itself had no detectable effect on Y cell response modes, prior parabrachial activation prevented the enhanced burstiness caused by chiasm stimulation. This parabrachial effect lasted for roughly 500 ms after stimulation. Neither chiasm nor parabrachial stimulation, singly or in combination, had a noticeable effect on the bursting activity of X cells. Finally, none of the extracellularly recorded retinogeniculate axons (23 X and 34 Y) showed any evidence of burst responses. This supports the conclusion that the burst responses we found for geniculate neurons represent an emergent property of the lateral geniculate nucleus, and this burstiness reflects an interruption of retinogeniculate transmission. We conclude that geniculate X and Y cells do indeed show evidence during extracellular recording of maintaining two very different response modes and that, under our recording conditions, Y cells are much more prone to burst activity than are X cells.

Notes: Summary Immunocytochemistry revealed that in the cat dorsal lateral geniculate nucleus (dLGN) almost all parvalbumin-positive cells are GABAergic and about 56% of the calbindin D-28K calbindin-immunoreactive neurons are also GABA-positive. On the other hand, in the same nucleus, almost all GABAergic neurons contain parvalbumin, and about 89% of the GABA-immunoreactive neurons contain calbindin. Double-labeling with calbindin and parvalbumin revealed that approximately 50% of the immunoreactive neurons are doublestained. In the PGN, virtually all neurons are GABA and parvalbuminpositive. Only a few scattered cells were also calbindin-immunoreactive. These results show that GABAergic geniculate cells can be differentiated on the basis of their calcium-binding protein immunoreactivity. Four types of immunoreactive cells are described here: (1) cells positive for GABA, parvalbumin and calbindin, (2) cells positive for GABA and parvalbumin, but negative for calbindin, (3) cells negative for GABA and parvalbumin, but positive for calbindin, (4) cells negative for GABA, parvalbumin and calbindin.

Notes: Summary Intersegmental limb dynamics and muscle activities were analyzed for consecutive cycles of paw-shake responses from chronic-spinalized cats to investigate how hindlimb trajectories organize into a pattern with regular oscillations, a steady-state response, or alternatively, into a pattern with irregular oscillations, a nonsteady-State response. In the spinalized preparation, steady-state and nonsteady-state responses have an equal likelihood of emerging from the initial cycles of a paw-shake response, suggesting that regular coupling of joint oscillations is not planned by pattern-generating networks within lumbosacral segments. To examine the characteristics of coupled and uncoupled limb oscillations during pawshake responses, we assessed patterns of muscle activity and hindlimb kinematics of six adult chronic-spinalized cats. Additionally, we used inverse-dynamics techniques to quantify the intersegmental dynamics of the paw, leg, and thigh. Our data indicate that by the second cycle of both steady-state and nonsteady-state responses, the basic pattern of interaction between muscle and motiondependent torques at the ankle and knee joints was established. During subsequent cycles of steady-state responses, a consistent sequence of timing changes occurred, such that, just prior to steady-state oscillations, torque maximums peaked simultaneously at each joint and joint reversals occurred simultaneously. Although nonsteadystate responses showed a similar sequence during beginning cycles, increased ankle muscle and net torques during middle cycles created larger inertial torques at the knee joint that were not counteracted and resulted in irregular and uncoupled knee oscillations. It is likely that neither steady-state nor nonsteady-state oscillations are planned by pattern-generating networks within lumbosacral segments, but that patterns of interjoint coordination emerge from the coupling among oscillators. For paw-shake responses in the spinalized preparation, coupling may depend on interactions between central circuits and motion-dependent feedback that is necessary to stabilize inertial effects due to large ankle joint accelerations.

Notes: Summary The morphology of single C3–C4 propriospinal neurones (PNs) including the cell body, dendritic tree, axonal trajectory and the pattern of projection and termination of axonal collaterals in the C3–C4 segments was investigated by intra-somatic or intra-axonal injection of horseradish peroxidase. All the C3–C4 PNs could be antidromically activated from the lateral funicle in C6 and the lateral reticular nucleus but not from Th13. Another criterion was that they received monosynaptic excitation from corticospinal fibres in the contralateral pyramid. Twenty-four C3–C4 PNs were successfully stained. They were located in the lateral part of laminae VI–VIII except for two neurones which were located in lamina V and two in lamina IX. Five to eleven dendrites originated from the cell bodies and extended throughout laminae IV–VIII and even into the white matter in the transverse plane and up to 3 mm rostro-caudally. The axonal trajectory from the cell body was usually curved before reaching the lateral funicle. The bifurcation of the stem axon into a descending and an ascending branch was mostly observed in the white matter close to or at the border between the white and grey matter at the level of the cell body. The ascending and descending axonal branches maintained their location in the same part of the lateral funicle. Sixteen out of 24 stem axons gave off collaterals in the grey matter and/or in the white matter. One to five collaterals were given off from the axons in the grey matter. Boutons were found in a restricted region in the intermediate zone from lamina VI to the border between laminae VII and VIII, in the lateral part of laminae V–IX, in the middle and medial parts of laminae VI–VIII. The termination in the vicinity of large neurones in lamina VIII suggests that long PNs receive collateral projections from the C3–C4 PNs. The finding that some collaterals terminated laterally in lamina IX is in agreement with electrophysiological observations that spinal accessory motoneurones receive disynaptic pyramidal excitation which is mediated via C3–C4 PNs. The collateral projection from the C3–C4 PNs to lateral and medial regions in laminae VI-VII is discussed in relation to feed-forward and feed-back inhibitory control of the C3–C4 PNs.

Notes: Summary 1. Eye movement responses were examined in alert cats during sinusoidal vertical linear acceleration. Stimulus frequencies of 0.20–0.85 Hz with a constant amplitude of 10.5 cm (corresponding to 0.02–0.31 g) were used. A random visual pattern was presented to give sinusoidal vertical optokinetic stimuli of similar amplitude and frequency to the up-down motion of the cat. 2. Sinusoidal linear acceleration in the presence of a stationary visual pattern produced robust eye movement responses with near compensatory phase at all stimulus frequencies tested. With both eyes covered, a vertical linear vestibulo-ocular reflex (LVOR) was frequently produced at a stimulus strength corresponding to 0.04–0.31 g. The evoked LVOR was always small, and the overall mean response phase values advanced by as much as 70 ° at frequencies below 0.56 Hz, indicating that the otolith signals activated by sinusoidal linear acceleration were not, by themselves, converted into compensatory eye position signals under these experimental conditions. 3. Optokinetic stimulation alone produced more lag of response phase as stimulus frequency increased, and the gain of evoked eye movement responses was smaller at higher stimulus frequencies compared to the gain during linear acceleration in the light. Bilateral labyrinthectomies resulted in a significant change of the eye movement responses during linear acceleration when visual inputs were allowed: there was more phase lag at higher stimulus frequencies and a decreased gain at all frequencies tested. These results indicate that the interaction of otolith and visual inputs produces robust eye movement responses with near compensatory phase during sinusoidal linear acceleration in the light.

Notes: Summary The distribution of cerebral cortical neurons sending projection fibers to the nucleus of the solitary tract (NST), and the topographical distribution of axon terminals of cortico-NST fibers within the NST were examined in the cat by two sets of experiments with horseradish peroxidase (HRP) and HRP conjugated with wheat germ agglutinin (WGA-HRP). First, HRP was injected into the NST. In the cerebral cortex of these cats, neuronal cell bodies were labeled retrogradely in the deep pyramidal cell layer (layer V): After HRP injection centered on the rostral or middle part of the NST, HRP-labeled neuronal cell bodies were distributed mainly in the orbital gyrus and caudal part of the infralimbic cortex, and additionally in the rostral part of the anterior sylvian gyrus. After HRP injection centered on the caudal part of the NST, labeled neuronal cell bodies were seen mainly in the caudoventral part of the infralimbic cortex, and additionally in the orbital gyrus, posterior sigmoid gyrus and rostral part of the anterior sylvian gyrus. The labeling in the infralimbic cortex, orbital gyrus and anterior sylvian gyrus was bilateral with a predominantly ipsilateral distribution, while that in the posterior sigmoid gyrus was bilateral with a clear-cut contralateral dominance. In the second set of experiments, WGA-HRP was injected into the cerebral cortical regions where neuronal cell bodies had been retrogradely labeled with HRP injected into the NST: After WGA-HRP injection into the orbital gyrus, presumed axon terminals in the NST were labeled in the rostral two thirds of the nucleus bilaterally with an ipsilateral predominance. After WGA-HRP injection into the rostral part of the anterior sylvian gyrus, a moderate number of presumed axon terminals were labeled throughout the whole rostrocaudal extent of the NST bilaterally with a slight ipsilateral dominance. After WGA-HRP injection into the middle and caudal parts of the anterior sylvian gyrus, no labeling was found in the NST. After WGA-HRP injection into the caudal part of the infralimbic cortex, presumed terminal labeling in the NST was seen throughout the whole rostrocaudal extent of the nucleus bilaterally with a dominant ipsilateral distribution. After WGA-HRP injection into the posterior sigmoid gyrus, however, no terminal labeling was found in the NST. The results indicate that cortico-NST fibers from the orbital gyrus terminate in the rostral two thirds of the NST, while those from the infralimbic cortex and the rostral part of the anterior sylvian gyrus project to the whole rostrocaudal extent of the NST.

Notes: Summary The aim of this study was to determine whether vestibular information related to head acceleration is available for triggering postural responses to perturbations of stance in the freely-standing cat. Linear accelerations of the head were recorded during postural responses evoked by linear translations of the support surface. A consistent initial peak of acceleration was observed at an average latency of 22 ms and magnitude of 0.03 g (g is acceleration due to gravity, 9.8 m/s/s). The acceleration peak preceded the first evoked EMG activity by an average of 24 ms. It was concluded that stimulation of the vestibular apparatus was both adequate and early enough for the vestibular system to have triggered the automatic postural response.

Notes: Summary Cats trained to stand on a platform exhibit postural responses to dynamic tilting that appear to be based on an internal reference model of body geometry and the environment rather than directly on sensory inputs, as in a classical reflex chain. The data presented show an independent control of global variables of limb geometry, the length and the orientation, resulting from a parallel processing of multisensory inputs into separate central representations of body tilt. Limb length and orientation changes have completely different response dynamics and can be decoupled by appropriate manipulation of sensory information about self-motion.

Notes: Summary The olivocerebellar projection to the c1,c2 and c3 zones in the paravermal cortex of lobule Vb/c has been investigated in the cat using a combined electrophysiological/neuroanatomical tracing technique. The zonal boundaries in the paravermal cortex were located by recording, on the cerebellar surface, climbing fibre field potentials evoked in response to percutaneous stimulation of one or more paws. A small (10–30 nl) injection of WGA-HRP was then made either into the centre or into the medial or lateral geographical half of a chosen zone and the resultant distribution of retrogradely labelled cells within the contralateral inferior olive was plotted. The c1 and c3 zones were each found to consist of two mediolaterally oriented ‘sub-zones’ which could be distinguished by their olivocerebellar input. The medial part of the c1 zone received climbing fibre input from the rostromedial part of the dorsal accessory olive (DAO) while the lateral part of the c1 zone received climbing fibre input from middle/rostral regions of the medial accessory olive (MAO). Both medial and lateral ‘sub-zones’ within the c3 zone were found to receive climbing fibre input from the rostral pole of DAO but, whereas there was heavy overlap between the olivary territories projecting to the medial c1 and medial c3 subzones, olivary cells projecting to the lateral part of c3 were located more rostrally within DAO. The c2 zone was found not to be divisible into mediolaterally oriented subzones and to receive climbing fibre input from a region of MAO located rostral and somewhat lateral to the region projecting to the lateral part of the c1 zone. The sub-zonal organisation of the olivocerebellar projection to the c1, c2 and c3 zones is discussed in relation to the functional properties of the different zones.

Notes: Summary The visual cortex of adult cats was studied physiologically following neonatal isochronic transplantation of grafts from areas 17,18, which were placed homotopically, in order to reveal their functional integration and thus possible repairing of damaged cortical neuronal circuits. Three homograft cats, in which transplantation was carried out between siblings (228 cortical cells) were compared to 4 animals receiving reimplanted autografts of the equivalent size (131 cells) as well as 3 animals with analogous sectioning of the visual cortex (162 cells) (pseudograft controls). The location of the boundaries between the transplant region and the host were determined using the Nissl's method for staining histological cross sections. Extracellular unit recording revealed typical waveform of the action potentials in the transplanted region and in the surrounding host tissue of all groups of cats. Visual responsiveness in the homograft cats was 17.5% in the transplanted region and 80.4% in the unoperated hemisphere; the corresponding results were 40.3% for the transplanted region and 82.2% for the unoperated hemisphere in the autografts and 23.1% and 73.4% in the pseudografts. The specificity of the cells to visual stimulation as expressed by their orientation and direction specificity, indicated preservation of these properties in the transplanted cats. While all responsive cells in the transplanted region of the homografts were orientation specific, their proportion was 60% in the autografts and 55.5% in the analogous region in the pseudograft controls. As to the direction specific cells, their performance in the grafted region of the grafted cats was even much higher than that of the pseudograft controls. The ocular dominance distribution of the cells showed preservation of binocularity in the transplanted region (90.0% binocular cells) of the homografts; it was however smaller in the equivalent region of the autografts (65.0%) and remarkably reduced (20.0%) in the pseudografts. It was concluded that despite the deafferentation induced during the transplantation procedure, a remarkable visual responsiveness was found in the transplanted region, indicating postoperative recovery. However, the cells there were mainly affected in their activity and less in their specificity to visual stimulation.

Notes: Summary Recent studies have shown that the interstitial nucleus of Cajal (INC) in the midbrain reticular formation is involved in the conversion of vertical semicircular canal signals into eye position during vertical vestibuloocular reflexes. Secondary vestibulo-ocular relay neurons related to the vertical canals, which constitute the majority of output neurons sending signals from the vestibular nuclei directly to the oculomotor nuclei, have been shown to project axon collaterals to the region within and near the INC. To understand how the INC is involved in the signal conversion, latencies of response of neurons in the INC region to electrical stimulaton of the vestibular nerve were examined in alert cats. The responses of 96 cells whose activity was clearly modulated by sinusoidal pitch rotation (at 0.31 Hz) were analyzed. These included 41 cells whose activity was closely correlated with vertical eye movement (38 burst-tonic and 3 tonic neurons), and 55 other cells (called pitch cells as previously). Twenty nine of the 96 cells (30%) were activated at disynaptic latencies following single shock stimulation of the contralateral vestibular nerve. Disynaptically activated cells were significantly more frequent for pitch cells than for eye movement-related cells (25/55 = 45% vs 4/41 = 10%; p 〈 0.001, Chi-square test). Conversely, cells that did not receive short-latency activation (〈 6 ms) were more frequent among eye movement-related cells than pitch cells (26/41 = 63% vs 13/55 = 24%; p 〈 0.001, Chi-square test). Pitch cells showed significantly less phase lag (re head acceleration) than eye movement-related cells during sinusoidal pitch rotation (mean ± SD 124° ± 17° vs 138° ± 14°. p 〈 0.01, t-test). These results suggest that 1) cells in the INC region other than burst-tonic and tonic neurons mainly receive direct inputs from secondary vestibulo-ocular relay neurons, and that 2) vertical canal signals reach eye movement-related neurons mainly polysynaptically.

Notes: Summary Efferent neurons of the cat superior colliculus (SC) which project in the predorsal bundle (PDB) and to the spinal cord (PDB neurons) form a major pathway by which the SC controls the changes of the direction of gaze in response to stimuli of visual and other modalities. Knowledge of rostrocaudal and lateromedial density distributions of different groups of PDB neurons within the SC is necessary to analyse their relationships with the topography of sensory and motor maps. Density gradients may also bear on the efficacy of connections originating from topographically different collicular regions. In the present study, large injections of HRP/ WGA-HRP were made in the C1 segment of the spinal cord and in the pontobulbar tegmentum. Judged by several morphological criteria, axons of passage, including those not subjected to a direct mechanical damage, were participating in the uptake of tracers. Therefore, labeled SC neurons corresponded to the nearly total populations of contralaterally projecting tectospinal neurons (TSNs) and neurons projecting in the PDB, respectively. Subtraction of the TSN density map from that of the whole PDB population was used to infer the distribution of tectal neurons terminating in the rhombencephalic tegmentum (TRhN). This subtotal labeling method proved useful in resolving the contradictions between the earlier HRP studies on the TSN and TRhN topography. The following density distributions were obtained for different groups of PDB neurons: 1) The mean TSN density is more than two times higher in the lateral half of the SC, representing the lower visual field. In this region the density remains constant from rostral to caudal, i.e., from the representation of vertical meridian to large contralateral azimuths. In the medial half, the average density decreases from rostral to caudal. Consequently, TSNs do not show the caudalward increment predicted by the higher efficacy of caudal stimulation points in eliciting head movements. 2) The distribution of PDB neurons is symmetrical with respect to the representation of the horizontal meridian. It is close to homogeneous at all azimuths of the retinotopic map and within the zone limited by small (10–15°) upward and downward elevations. There are clear density decrements towards the representation of greater elevations. We conclude that the assumption of homogeneous distribution of efferent neurons, made in the models of the primate SC, is valid in the cat, but only for the whole population of neurons projecting in the PDB and within the area representing the proximity of the horizontal meridian. The same restrictions apply to the validity of the translation invariance principle. 3) The distribution of TRhNs, obtained by subtraction, shows a tendency to higher densities in the caudal half of the SC, and a clear bias towards its medial zone, including the representation of the horizontal meridian and upper visual field. The different types of asymmetry in TRhN and TSN populations may be related to different types of head movements depending, respectively, on distant and near stimuli in the upper and lower visual fields.

Notes: Summary Excitation and inhibition of jaw-closing motoneurons (Masseteric and Temporal Motoneurons, Mass. and Temp. Mns) during transient jaw closing, the so-called jaw-closing reflex, and prolonged jaw opening elicited by palatal stimulation were studied. By pressing the anterior palatal surfaces sustained jaw opening was elicited, suggesting that sustained jaw opening results from inhibition of tonic background activity of jaw-closing motoneurons by inhibitory postsynaptic potentials (IPSPs) elicited by mechanical stimulation of the anterior palatal mucosa. Recordings showed that the onset of IPSPs was 80 ms earlier than the onset of jaw opening. Application of diffuse pressure stimulation to the posterior palatal surfaces elicited bursts of spikes triggered on excitatory postsynaptic potentials (EPSPs), suggesting that mechanosensory receptors from the posterior palatal mucosa send excitatory synaptic inputs to jaw-closing motoneurons. Furthermore, it is suggested that mechanosensory inputs from the posterior palatal mucosa may excite neurons in the central pattern generator and provide the motor patterns responsible for jaw closure during the jaw-closing reflex. We have demonstrated that excitation of Mass. Mns innervating the deep masseter muscle mainly contributed to maintaining the occlusal phase of jaw closure during the jaw-closing reflex. However, the onset of EPSPs was 100 to 160 ms (n = 27) earlier than the onset of jaw closure. In studies on spontaneously occurring jaw closure it was demonstrated that there was a proportional increase in the number of spikes of the Temp. Mn and the mechanical response (jaw closure).

Notes: Summary Low threshold (≤2×T) cutaneous afferents in the superficial peroneal (SP) and medial plantar (PLNT) nerves both produce short-latency excitatory postsynaptic potentials (EPSPs) in flexor digitorum longus (FDL) α-motoneurons, with minimum central latencies (≤1.8 ms) that indicate a disynaptic connection. However, SP and PLNT EPSPs in FDL motoneurons are differentially modulated during fictive stepping in decerebrate cats. The early components in SP EPSPs are systematically enhanced during the early flexion phase of fictive stepping (Schmidt et al. 1988) while those in PLNT EPSPs are markedly depressed during flexion. In addition, transmission in the PLNT→FDL pathway is enhanced during occasional step cycles in which the FDL displays firing during the extension phase. This enhancement affects only the trisynaptic components of PLNT EPSPs, is simultaneous with the extension FDL burst, and is not found in SP EPSPs. These results indicate that the SP→FDL and PLNT→FDL pathways are composed of entirely different sets of segmental last-order interneurons, each of which receives sensory information from contiguous, relatively limited regions of skin on the most distal parts of the hindpaw. Possible functional consequences of these interneuronal organizations are discussed.

Notes: Summary Flexion and extension movements were evoked in the elbow joint of unanesthetized cats by intracortical microstimulation (ICMS) applied to deep layers of the motor cortex (areas 4 and 6). Pulse trains with duration up to 3–4 s, current intensities of 15–50 μA and rates of approximately 100/s were used. Cortically evoked movements (CEMs) were tested mechanically by applying servo-controlled torque disturbances to the joint. The disturbances consisted of two reciprocating sinusoidal pulses of torque with fixed frequencies (1.2 or 3.2 Hz). A pronounced torque-angle hysteresis with long-lasting after-effects was revealed in the presence of the torque disturbances that opposed the CEMs and/or assisted them. Two parameters were introduced to describe the mechanical testing of the CEMs quantitatively: (1) the resulting stiffness (RS) denned during the forward and reverse phases of the disturbed movement as a ratio between the amplitudes of torque wave and the overal change of angle at these phases; (2) uncertainty index (UI) defined as the subtraction of forward and reverse angle changes, which was normalized by the first of these two values. RS was shown to be dependent on the immediate past movement history of the joint, it increased with changes in the direction of movement, and its magnitude during such changes could be several times higher than when the disturbance was in the same direction as the movement. When the directions of the preceding movement and the initial phase of the disturbed one coincided, a steady divergence between joint angles before and after application of the torque disturbance occurred, and the mean values of UI obtained in the experiment with various combinations of torque disturbances ranged from 0.52 to 0.8. In the same experiment when torque disturbances opposed the preceding movement, the reactions were significantly more unstable and the mean values of UI varied from +0.07 to -0.62. The possible mechanisms of the observed hysteresis and its role in motor control are discussed. Thixotropy of the muscle is considered to be the main factor of these effects. The muscle hysteresis seems to be significantly increased by a corresponding behaviour of the muscle spindles, this leads to a pronounced asymmetry of stretch and unloading reflexes acting on spinal and supraspinal levels. Based on the data obtained, it could be concluded that muscle hysteresis and its influence on the overal motor performance should not be ignored. Application of the so-called spring model of muscle and the equilibrium point hypothesis can lead to a mistaken treatment of experimental results in various motor control problems.

Notes: Summary 1. A total of 43 neurons that showed a close correlation with vertical eye movement with a burst-tonic or tonic type response during spontaneous saccades, were recorded within, and in the close vicinity of, the interstitial nucleus of Cajal (INC) in alert cats. Neuronal responses to sinusoidal vertical linear acceleration (0.2–0.85 Hz, amplitude 10.5 cm) and optokinetic stimuli (0.1–1.0 Hz, amplitude 10.5 cm), were examined. 2. All 43 eye movement-related neurons responded to sinusoidal vertical linear acceleration in the presence of a stationary visual pattern in correlation to robust eye movement responses with compensatory phase. Phase and gain values (re stimulus position) of response of individual cells were independent of the stimulus frequencies tested. Of these, 33 cells were examined during linear acceleration without visual input. Most cells (27/33) did not respond even when a weak linear vestibulo-ocular reflex was present (6/27). The remaining 6 cells (6/33) responded to linear acceleration. Their mean phase values advanced by 80 ° and gain dropped by 55% compared to the responses with visual inputs. 3. Twenty eight of the 43 cells were examined during vertical optokinetic stimuli. The activity of all 28 cells was modulated in correlation to eye movement responses. Response phase showed more lag, and gain decreased as stimulus frequencies increased, similar to optokinetic eye movement responses. 4. The close correlation between the activity of eye movement-related neurons in the INC region and robust eye movements during linear acceleration with visual inputs and optokinetic stimuli suggest that these neurons are involved in some aspect of vertical eye position generation during such stimuli.

Notes: Summary 1. In the chloralose anesthetized cat, conditioning stimulation of group I flexor afferents depresses the monosynaptic potentials generated by Ia afferents in single spinal motoneurons or in populations of motoneurons without affecting the monosynaptic potentials produced by stimulation of descending fibers in the ipsilateral ventromedial fasciculus (VMF). 2. Heterosynaptic facilitation of monosynaptic reflexes was used to test changes in the presynaptic effectiveness of excitatory inputs with direct connections with motoneurons. We found that the heterosynaptic facilitation of Ia origin was reduced by conditioning stimulation of group I afferents from flexors, without affecting the heterosynaptic facilitation produced by stimulation of the VMF. 3. These results confirm and expand previous observations showing that the synaptic effectiveness of descending fibers synapsing with motoneurons is not subjected to a presynaptic control mechanism of the type acting on Ia fiber terminals, and provide further basis for the use of changes in heterosynaptic facilitation of monosynaptic reflexes of Ia origin as an estimate of changes in presynaptic inhibition of Ia fibers (Hultborn et al. 1987a).

Notes: Summary 1. In cats anesthetized with alpha-chloralose, population synaptic responses of motoneurons produced by stimulation of group I afferents were recorded from ventral roots with a sucrose gap or extracellularly from the motor pool. These responses were depressed, and often abolished, following the intravenous injection of 1–3 mg/kg of (−)-baclofen, a presumed GABAb agonist. 2. The monosynaptic population responses of motoneurons produced by stimulation of the ipsilateral ventromedial funiculus (VMF), the bulbar reticular formation or the vestibular nucleus, were also depressed following the administration of (−)-baclofen, but to a lesser degree than responses produced by stimulation of group I fibers. 3. Depression of the synaptic actions of Ia and of descending fibers following the administration of (−)-baclofen occurred without significant changes in the presynaptic volley recorded from the cord dorsum. However, in 3/4 experiments the intraspinally recorded Ia terminal potential was reduced following the injection of (−)-baclofen. The VMF terminal potentials were also depressed, but to a lesser degree. 4. Intracellular recordings from spinal motoneurons indicate that the (−)-baclofen-induced depression of the monosynaptic Ia- and VMF-EPSPs occurred without important changes in the time course of EPSP decay. This suggests that with the amounts used, postsynaptic changes were not contributing significantly to the EPSP depression. 5. It is suggested that (−)-baclofen depresses synaptic transmission probably by activation of GABAb receptors located at the intraspinal terminations of Ia and descending fibers. The lower sensitivity of VMF actions to (−)-baclofen would be accounted for by a relatively low density of baclofen receptors in descending fiber terminals.

Notes: Summary Previous experimental evidences showed that the caudate nucleus has a modulatory effect on hippocampal epilepsy. The caudate's regulating action might reach the hippocampus either via the septal region or, retrogradely, via the accumbens nucleus. In order to obtain new data about the pathway involved in caudate hippocampal influence the spreading of abnormal activity towards the nucleus accumbens was studied. Furthermore the effects of caudate stimulation in animals with electrolytic lesions of the nucleus accumbens were analyzed. It was observed that abnormal penicillin-induced activity spreaded from the hippocampus to the nucleus accumbens in about 30 minutes. In animals with and without lesions of nucleus accumbens, caudate stimulation brought about a significant decrease in the frequency and amplitude of hippocampal activity. The results suggest that the nucleus accumbens is reached by the spreading of hippocampal epilepsy but does not participate in the control exerted by the caudate nucleus on the hippocampus. Thus the caudate-induced inhibition takes place through an anterograde caudate-hippocampal circuit, while at the same time excluding retrograde activation by way of a caudate-accumbens-hippocampal pathway.

Notes: Summary The biceps femoris (BF) muscle is divided into three neuromuscular compartments defined by the innervation patterns of the main nerve branches (English and Weeks 1987). The goals of this study were i) to determine how different regions of the biceps femoris muscle are activated in the intact cat during a broad range of limb movements evoked by perturbations of stance posture, and ii) to determine the relationship between the anatomical compartments of biceps femoris and the functional units as defined in this task. Cats were trained to stand on a moveable platform with each paw on a triaxial force plate. The animal's stance was perturbed by linear translation of the platform in each of sixteen different directions in the horizontal plane. EMG activity was recorded from eight sites across the width of the left biceps femoris muscle. During quiet stance only the anterior compartment was tonically active, presumably contributing to hip extensor torque in the maintenance of stance. During platform translation, evoked EMG activity was recorded from each electrode pair for a wide range of directions of perturbation; as direction changed progressively, the amplitude of evoked activity from any electrode pair increased to a maximum and then decreased. When the EMG amplitude was plotted in polar coordinates as a function of translation direction, the region of response formed a petal shaped area in the horizontal plane, termed the EMG tuning curve. The compartments of the BF muscle were not activated homogeneously. The tuning curve of the anterior BF compartment was similar to that of other hip extensors, and coincided with the region of postero-lateral force production by the hindlimb against the support. The tuning curve of the middle BF compartment was shifted in a counterclockwise direction from that of the anterior compartment, but overlapped extensively with it; the middle BF tuning curve was similar to that of anterior gracilis. The tuning curve of the posterior biceps compartment was rotated further counterclockwise and overlapped very little with that of the middle BF compartment. The posterior BF was activated in a pattern similar to that of other knee flexors. The functional units of BF activation were not identical with the neuromuscular compartments defined by the main nerve branches. As direction of the perturbation changed, the region of BF that was activated moved progressively across the muscle. This progression of the active region was continuous across BFa and BFm, whereas there was a jump, or discontinuity at the border between BFm and BFp. Thus, differences in activation were observed not only across compartments, but also within compartments, and different regions of the BF muscle were activated independently during responses to postural perturbations.

Notes: Summary We have recorded the direction of optokinetic nystagmus (OKN) elicited by moving plaid patterns in order to dissociate the pathways that mediate horizontal OKN. The plaids used comprised two drifting sinusoidal gratings arranged such that their individual directions of drift were very different from the direction of coherent motion of the overall pattern. The direction of OKN with binocular viewing was close to the mean of the component directions, suggesting a dominant influence of cortical visual neurons that respond to oriented one-dimensional components of the image. But the direction of OKN was consistently shifted slightly towards the direction of motion of the overall pattern, suggesting a secondary influence responsive to pattern direction. OKN recordings obtained during monocular viewing suggest that this secondary influence reflects the direct retinal pathway to the brainstem structures mediating OKN.

Notes: Summary The origin and laminar arrangement of the homolateral and callosal projections to the anterior (AAF), primary (AI), posterior (PAF) and secondary (AII) auditory cortical areas were studied in the cat by means of electrophysiological recording and WGA-HRP tracing techniques. The transcallosal projections to AAF, AI, PAF and AII were principally homotypic since the major source of input was their corresponding area in the contralateral cortex. Heterotypic transcallosal projections to AAF and AI were seen, originating from the contralateral AI and AAF, respectively. PAF received heterotypic commissural projections from the opposite ventroposterior auditory cortical field (VPAF). Heterotypic callosal inputs to AII were rare, originating from AAF and AI. The neurons of origin of the transcallosal connections were located mainly in layers II and III (70–92%), and less frequently in deep layers (V and VI, 8–30%). Single unit recordings provided evidence that both homotypic and heterotypic transcallosal projections connect corresponding frequency regions of the two hemispheres. The regional distribution of the anterogradely labeled terminals indicated that the homotypic and heterotypic auditory transcallosal projections are reciprocal. The present data suggest that the transcallosal auditory interconnections are segregated in 3 major parallel components (AAF-AI, PAF-VPAF and AII), maintaining a segregation between parallel functional channels already established for the thalamocortical auditory interconnections. For the intrahemispheric connections, the analysis of the retrograde tracing data revealed that AAF and AI receive projections from the homolateral cortical areas PAF, VPAF and AII, whose neurons of origin were located mainly in their deep (V and VI) cortical layers. The reciprocal interconnections between the homolateral AAF and AI did not show a preferential laminar arrangement since the neurons of origin were distributed almost evenly in both superficial (II and III) and deep (V and VI) cortical layers. On the contrary, PAF received inputs from the homolateral cortical fields AAF, AI, AII and VPAF, originating predominantly from their superficial (II and III) layers. The homolateral projections reaching AII originated mainly from the superficial layers of AAF and AI, but from the deep layers of VPAF and PAF. The laminar distribution of anterogradely labeled terminal fields, when they were dense enough for a confident identification, was systematically related to the laminar arrangement of neurons of origin of the reciprocal projection: a projection originating from deep layers was associated with a reciprocal projection terminating mainly in layer IV, whereas a projection originating from superficial layers was associated with a reciprocal projection terminating predominantly outside layer IV. This laminar distribution indicates that the homolateral auditory cortical interconnections have a feed-forward/feed-back organization, corresponding to a hierarchical arrangement of the auditory cortical areas, according to criteria previously established in the visual system of primates. The principal auditory cortical areas could be ranked into 4 distinct hierarchical levels. The tonotopically organized areas AAF and AI represent the lowest level. The second level corresponds to the non-tonotopically organized area AII. Higher, the tonotopically organized areas VPAF and PAF occupy the third and fourth hierarchical levels, respectively.

Notes: Summary Spatial-frequency dependence of directional tuning and directional bias was compared, for both eyes, in four previously established discrete classes of binocular feline striate cortical neurones. Two classes (respectively direction-selective or bidirectional at optimal spatial frequency) were directionality invariant at all spatial frequencies. In the remaining two classes, both directionbiased at optimal spatial frequency, directional bias either altered or reversed with change in spatial frequency. In all four classes, the directional tuning of a majority of neurones sharpened at high spatial frequency through either eye, although the bandpass characteristics were sometimes dissimilar for the two eyes. All neurones were of the same type through either eye. Amongst the two classes of direction-biased neurones, the strength of bias was commonly different through the two eyes. Where reversal of bias occurred, that reversal took place at different spatial frequencies for each eye. Thus, the direction and orientation preferences of cortical neurones are fixed at optimal spatial frequency, but their envelope of tuning to a gamut of spatial frequencies is not. These differences are potentially related to binocular coding of visual perspective, including dynamic object rotation in visual space.

Notes: Summary We studied the ocular dominance distribution in visual cortex of kittens which had been monocularly exposed to moving-pattern stimuli under anesthesia and paralysis. 1. We did not obtain any discernible changes in ocular dominance, confirming the previous reports that anesthesia and paralysis prevent ocular dominance plasticity from occurring. 2. The plasticity, however, was restored under the acute experimental condition by a cortical infusion of 1-noradrenaline (1-NA). In the 1-NA-infused visual cortex, the ocular dominance distribution was clearly shifted to the open eye after monocular exposure for about 20–24 h. 3. We also studied how quickly and to what extent the changes were induced when the duration of the combined treatment was varied. The results were: (i) the earliest change was observed in ∼ 12 h with disappearance of binocular cells, (ii) the treatment was most effective after 20–24 h in inducing the shift of ocular dominance, and (iii) the treatment longer than 24 h (up to 45 h) did not necessarily enhance the shift, though the state of reduced binocularity was sustained throughout. 4. The effects of the cortical 1-NA infusion combined with monocular exposure became less with increasing the age of experimental animals, suggesting the presence of the “susceptible period” in the acute experiments. 5. The effects seemed to become smaller toward the end of a given recording session, suggesting that the restored plasticity wanes with time. The present results further support the idea that the direct activation of the NA system enhances cortical plasticity, in principle, independent of general conditions of experimental animals.

Notes: Summary Sensitivity to binocular positional mismatch was evaluated in cat striate cortical neurones, for paired, dichoptically presented, moving sine-wave gratings whose interocular positional phase relationship was varied. Spatial frequency, orientation and velocity were optimized for each neurone. Binocular responses for each spatial phase were compared with monocular stimulation of either eye. Binocular responses ranged from facilitation, through complete or partial summation, to partial or binocular occlusion. Counter to previous reports, all functional classes of neurones (simple neurones; special, intermediate and standard complex neurones) were represented in phase-specific and phase-insensitive groups. Most simple neurones, together with a small minority of standard complex neurones, exhibited near-total phase-sensitive modulation, the most significant new finding being that a minority of simple neurones were relatively insensitive to binocular mismatch. The majority of complex neurones, of all types, showed shallower modulation depths (typically around 30%), distributed in a continuum, with no indication of bimodality. It is concluded that the property of positional sensitivity is not attributable solely to simple neurones; and that positional insensitivity is not seen only in complex neurones. At least some neurones of all functional categories evince either kind of behaviour. These results are interpreted as a two-stage mechanism for convergence and matching of inputs from the two eyes.

Notes: Summary Using intracellular recording techniques, we studied the response characteristics of two separate populations of triceps surae motoneurons in unanesthetized decerebrate cats, recorded before and after low thoracic hemisection of the spinal cord. In each preparation, we studied the response properties of one group of motoneurons and the protocol was then repeated for a separate group, immediately following the dorsal hemisection. In each group, we examined both the minimum firing rates of motoneurons during intracellular current injection and a range of cellular properties, including input resistance, rheobase current and afterhyperpolarization time course and magnitude. Although earlier studies from this laboratory have shown substantial reductions in minimum firing rate in reflexively active motoneurons in the hemisected decerebrated preparation, the response of motoneurons to intracellular current injection in the current preparation proved to be quite different. Minimum firing rates were either normal or even somewhat higher in the post-lesion group, while the time course of the afterhyperpolarization was shortened. Moreover, these effects were not evenly distributed across the motoneuron pool. The rate effect was most evident in motoneurons with higher conduction velocity, while the afterhyperpolarization effect occurred predominantly in motoneurons with lower conduction velocity. Neither of these effects could be accounted for by lesion-induced changes in other cellular properties. We conclude that tonically active neurons with descending axons traversing dorsolateral white matter may influence both the discharge characteristics and membrane properties of spinal motoneurons in novel ways, presumably by modifying voltage or calcium activated motoneuronal conductances. The previously described reactions in the the firing rate of motoneurons after such lesions appear to be mediated by different means, perhaps by alterations in synaptic input from segmental interneurons.

Notes: Summary As part of our studies of the spinal circuitry of the tonic neck reflex, we have recorded extracellularly from Ia reciprocal inhibitory neurons of the decerebrate, labyrinthectomized cat. The activity of a majority of neurons driven by stimulation of the quadriceps nerve was modulated by sinusoidal rotation of the neck; such modulation was much less frequent in the case of neurons driven by stimulation of nerves to more distal muscles. The results suggest that some of the inhibition which is part of the tonic neck reflex is mediated by Ia reciprocal inhibitory neurons, but that other pathways must also play an important role.

Notes: Summary During a critical period of postnatal development the visual cortex of kittens is susceptible to experience-dependent modifications of neuronal response properties. Evidence is accumulating that these modifications are triggered by a transient neuronal calcium (Ca) influx. To further investigate this issue we measured extracellular Ca concentrations with ion-sensitive microelectrodes and compared the magnitude and the distribution of stimulus-evoked Ca fluxes in slices of the visual cortex of 4- to 5-week-old kittens and of 6-month-old adult cats. Stimulation of the white matter at 15 Hz for 8 s caused transient decreases of the extracellular Ca concentration (Δ Ca0) in slices of both age groups and in all cortical layers. However, there were developmental changes in the laminar distribution of the Δ Ca0: in kittens, they were maximal in layer IV whereas in adult cats they were most pronounced in the supragranular layers. The ratios between the amplitudes of ΔCa0 in layer IV and the supragranular layers were 1.65 ± 0.26 in kittens and 0.43 ± 0.2 in adult cats. These changes in laminar distribution resemble the laminar specific decay of neuronal malleability and parallel the developmental redistribution of 1,4-Dihydropyridine-sensitive Ca channels. Because of these correlations we interpret our findings as support for the hypothesis that experience-dependent modifications are triggered by Ca influx.

Notes: Summary Layer VI of the visual cortex has been considered to be dominated by cells with very long receptive fields, typically summing to 8° or more. We have re-examined this issue in a series of experiments in which the length tuning profiles of layer VI cells in the cat visual cortex have been quantitatively determined. Responses were assessed to optimally oriented bars of light of varying length drifted over the receptive field. The lengths were varied on a randomised interleaved sequence. Although our data confirm the presence of long field cells in layer VI, only 24% of a population of 119 cells had fields greater than 6° in length. Fields greater than 8° were only seen in 17% of cells. 61% of the population of cells had fields showing summation to 4° or less with a mean length of 2.8° (+ / -0.15 sem). In this “short field” group, 18% had fields of 1° or less. We observed 7 cells with rapid initial spatial summation up to 1°, followed by clear end zone inhibition. It has been recently suggested on the basis of localised inactivation experiments, that layer VI cells with long (〉 8°) fields may provide the drive to inhibitory interneurones in layer IV generating hypercomplex cell end zone inhibition. This observation is difficult to equate with evidence indicating that hypercomplex cell end zone inhibition reflects a mechanism showing maximal summation at lengths in the region of 2.8°. The present data show layer VI to possess cells capable of providing the drive for hypercomplex cell end zone inhibition in layer IV.

Notes: Summary The superficial layers of the cat's superior colliculus innervate the medial subdivision of the thalamic lateral posterior nucleus (LPm). LPm is set off from adjoining thalamic zones by its denser staining for acetylcholinesterase (AChE). We sought to learn whether the tectal afferents to LPm might themselves be the source of the enzyme staining by examining the effects of collicular lesions on the thalamic staining pattern. Large excitotoxin lesions of the colliculus largely eliminated AChE staining in the ipsilateral LPm. By contrast, fibersparing lesions of LPm itself left AChE staining nearly unchanged. Destruction of collicular neurons by excitotoxins dramatically reduced AChE staining in fibers of the brachium and superficial gray layer of the superior colliculus. The reduction was especially pronounced in the lower part of the superficial gray layer, in which LP-projecting collicular neurons are located. These results are consistent with the view that LP-projecting collicular neurons synthesize AChE and account for much of the histochemically detectable enzyme present both in the lower superficial gray layer and in LPm. In the colliculus, the excitotoxin lesions spared AChE staining in a thin sheet at the upper border of the superficial gray layer and in the enzyme-positive patches in the intermediate layers. This surviving tectal AChE thus is probably presynaptic and could be contained at least partly in cholinergic afferents from the parabigeminal nucleus and pontomesencephalic tegmentum. The collicular lesions had no obvious effect on AChE staining in the parabigeminal nucleus or in the C-laminae or ventral division of the lateral geniculate nucleus.

Notes: Summary Periodontal mechanosensitive units (PM units) were recorded from the trigeminal main sensory nucleus (Vms) of the cat. The receptive fields of PM units were arranged from mandibular to maxillary divisions dorso-ventrally. The majority of PM units were single tooth units responsive to the canine tooth. They were directionally selective and had sustained responses to pressure applied to the tooth. The optimal stimulus direction of maxillary and mandibular PM units when the canine tooth was stimulated was single and it was oriented predominantly in the caudio-medial or rostrolateral direction. The threshold intensity of canine tooth stimulation was less than 0.05 N in most of the units. These findings indicate that the response properties of PM units in the Vms resemble fairly closely those of the primary afferent nerves arising from the periodontal mechanoreceptors.

Notes: Summary Horizontal and vertical eye movements were recorded in alert, restrained cats that were subjected to whole-body rotations with the horizontal semicircular canals in the plane of rotation and the body centered on the axis or 45 cm eccentric from the axis of rotation. Changes in the horizontal vestibulo-ocular reflex (HVOR) due to the resultant of the linear forces (i.e., gravity and linear acceleration) acting on the otolith organs were examined during off-axis rotation when there was a centripetal acceleration along the animal's interaural axis. The HVOR time constant was slightly shortened when the resultant otolith force was not parallel to the animal's vertical axis. This effect was independent of the direction of the otolith force relative to the direction of the slow phase eye velocity. No effect on the HVOR amplitude was observed. In addition to changes in the HVOR dynamics, a significant vertical component of eye velocity was observed during stimulation of the horizontal canals when the resultant otolith force was not parallel with the animal's vertical axis. The effect was greater for larger angles between the resultant otolith force and gravity. An upward or downward component was elicited, depending on the direction of the horizontal component of eye velocity and the direction of the resultant otolith force. The vertical component was always in the direction that would tend to align the eye velocity vector with the resultant otolith force and keep the eye movement in a plane that had been rotated by the angle between the resultant otolith force and gravity.

Notes: Summary The vertical and horizontal components of the vestibulo-ocular reflex (VOR) were recorded in alert, restrained cats who were placed on their sides and subjected to whole-body rotations in the horizontal plane. The head was either on the axis or 45 cm eccentric from the axis of rotation. During off-axis rotation there was a change in the linear force acting on the otolith organs due to the presence of a centripetal acceleration along the animal's vertical axis. Otolith forces (defined to be opposite to the centripetal acceleration) directed ventrally with respect to the animal (negative) decreased both the amplitude and time constant of the first-order approximation to the slow phase eye velocity of the vertical vestibulo-ocular reflex (VVOR). Otolith forces directed dorsally (positive) increased the amplitude and time constant. The effects were greater for the up VOR. The asymmetry in the VVOR time constant also depended on the otolith forces, being less in the presence of negative otolith forces that caused the resultant otolith force to move ventrally, towards the direction along which gravity normally acts when the animal is in the upright position. The effects of otolith forces on the up VVOR were independent of whether the animals were tested in the dark or in the light with a stationary visual surround (i.e., during visual suppression). In contrast, the changes in the time constant of the down VVOR were smaller during visual suppression. Simulations of the eye velocity storage mechanism suggest that the gain of the feedback in the storage integrator was modified by the angle between the resultant otolith force and an animal-fixed reference. This could be the animal's vertical, i.e., the direction along which gravity normally acts. For larger angles the feedback was less and the amplitude and time constant of the VVOR increased. The transformation of the otolith input was the same for both the up and down VOR, even though the final effect on the eye velocity was asymmetric (larger for up VOR) due to a separate, asymmetric gain element in the velocity storage feedback pathway.

Notes: Summary The activity of 61 rubral neurones was recorded in association with microinjections of GABA, muscimol, bicuculline-methiodide or saline, in cat Red Nucleus area, during the performance of a reaction time task. The depressing action of GABA and muscimol on the firing of most neurones (17/23) suggests that, in a behavioural situation, an inhibitory GABAergic control can be exerted on rubral neurones discharging with different patterns during the reaction time task. The motor slowing down induced by GABA and muscimol is in agreement with a general reduction of the rubral output. Injections of bicuculline, whose antagonistic effects on GABA transmission are well established in the Red Nucleus, had various consequences on the firing of rubral neurones: 1) the decreases of activity related to the reaction time task were never suppressed, suggesting that these task-related inactivations are probably not mediated by GABA A receptors; 2) an enhancement of the tonic and phasic discharges was found for 1/4 of the neurones (7/29), which were either activated or not modulated in relation to the reaction time task, suggesting that a sustained GABA A-mediated inhibition, blocked by bicuculline, could be exerted on these neurones; 3) a reduction of the tonic and phasic discharges was observed for other neurones (15/29), which were either activated, inactivated or not modulated in relation to the reaction time task, suggesting that the activity of these neurones could be controlled by inhibitory processes not mediated by GABA A receptors, possibly enhanced or released by bicuculline. The delay in motor triggering induced by bicuculline could be related to the disruption of the pattern or rubral output during the reaction time task, as a result of the opposite changes affecting the firing of rubral neurones. A well-balanced GABAergic activity appears to be critical in the control of rubral firing during the performance of the reaction time task.

Notes: Summary Microinjections of D,L homocysteic acid (DLH, 40 nmoles) made in the lateral PAG of the unanesthetized and paralyzed decerebrate cat evoked distinct patterns of extracranial and hindlimb blood flow. One pattern, evoked from the pretentorial part of the lateral PAG (A3.3-A2.5), consisted of an extracranial vasodilation associated with an iliac vasoconstriction. Another pattern, evoked from the subtentorial part of the lateral PAG (P0.2–P0.9), consisted of an extracranial vasoconstriction associated with an iliac vasodilation. Both patterns were associated with increased arterial blood pressure. These results indicate (i) that the PAG contains neurons regulating head and hindlimb vasculature, and (ii) that these neurons are viscerotopically organized, in the sense that different representations of the head and hindlimb are found at different rostrocaudal levels. The significance of the results is discussed in the context of our previous findings that different kinds of defense reactions are evoked from these same pretentorial and subtentorial PAG regions.

Notes: Summary 1) The response characteristics of periodontal mechanosensitive neurons in the thalamic nucleus were studied by using 15 adult cats anesthetized with alphachloralose (40 mg/kg, i.v.). 2) 468 periodontal mechanosensitive units (PM units) responsive to light mechanical stimulation of the teeth were recorded from a medioventral aspect of the nucleus ventralis posteromedialis (VPM). Of these neurons, 213 units (45.5%) were slowly adapting, and 255 units (54.5%) were rapidly adapting. 3) The receptive field of the PM units was represented by the number of receptive quadrants on the dental arches of both jaws. About half of the PM units (279, 59.6%) were one-quadrant units. Of these neurons, 69 (14.7%) were single tooth units. Two-quadrant, three-quadrant and four-quadrant units numbered 123 (26.3%), 3 (0.6%) and 63 (13.5%) respectively. Of the PM units detected, 246 units (52.6%), 124 units (26.4%) and 98 units (20.9%) responded to mechanical stimulation of the teeth on only the contralateral side, on only the ipsilateral side and on both sides, respectively. 4) One-quadrant units were distributed mainly in the rostral part of the PM area, and four-quadrant units were found in the caudal part of the PM area. A somatotopic organization for each tooth was not found. 5) The incidence of single tooth units in the thalamus was extremely low, compared with those in the primary afferents and in the trigeminal nuclear complex. Most of the thalamic neurons had larger receptive fields than both the primary afferents and the trigeminal nuclear complex neurons. 6) The high incidence of fourquadrant units at the caudal part of the PM area suggests that many PM fibers converge there. However, it is still unclear whether these fibers come through the intrathalamic neurons or directly from the trigeminal nuclear complex.

Notes: Summary Acetylcholinesterase (AChE) activity, demonstrated histochemically, defines an area of cortex on the middle ectosylvian gyrus that appears to correspond to the cytoarchitectonically defined area 41 and the physiologically defined primary auditory area (AI). In this area there are high levels of AChE in layers III, IV and VI while in the surrounding areas there are comparatively low levels of enzyme in these layers. The monoclonal antibody CAT 301, which was raised against a cell surface proteoglycan, also defines this area. There are high levels of CAT 301 immunoreactivity in cell bodies and the neuropil of layer III and an absence of very large immunoreactive neurons in layer V. Furthermore there are higher levels of the calcium binding protein, parvalbumin and the metabolic enzyme, cytochrome oxidase, in layers III and IV of AI, than in most of the surrounding cortex. By contrast the distribution of the calcium binding protein, calbindin and the distribution of myelinated fibers are similar in area 41 and the surrounding areas.

Notes: Summary Retinotopy and binocular responsiveness were studied extracellularly in a total of 278, 61, 110 and 275 cells sampled in areas 17, 18, 19 and Clare-Bishop (CB) of Siamese cats. The misalignment of the visual axes of the two eyes was determined by the pupil reflex method in the behaving animal. The recording sessions were conducted under N2O anesthesia, supplemented with continuous infusion of short-lasting anesthetics (Saffan, Glaxo) and muscle relaxants (Gallamine triethiodide) using two types of visual stimulators presenting two-dimensional (2D) motion stimuli and the visual cues for three-dimensional (3D) motion. All of the nine Siamese cats demonstrated Boston type retinotopic abnormalities in all of cortical areas 17–19 and CB. Very few binocular cells were present in areas 17–19 and the posterior (A1-P2) CB but they were numerous in most of CB (A9-4). A significant fraction (36/78) of binocular cells in the major CB of the Siamese cats demonstrated similar response selectivity to that reported in normal CB cortex for stimulation with the 3D motion cues under both null disparity and strabismic conditions (binocular receptive fields for two eyes were optically superposed or separated by the strabismic angles estimated in the individual animals). These findings indicate that the binocular signals converging to the CB cells through different pathways (signals coming from the contralateral eye via the ipsilateral hemisphere including the interlaminar nucleus and areas 17–19, and commissural signals from the ipsilateral eye via the contralateral areas 17–19 and CB) were integrated to yield useful information for the recognition of 3D motion, and that the major CB is an actual site of binocular integration at least in Siamese cats, rather than being merely a reflection of the information processing before the CB cortex.

Notes: Summary Small iontophoretic injections of the lectin, Phaseolus vulgaris leucoagglutinin (PHA-L), were made into different layers of the primary auditory cortex (AI) of cats. Injections in layer I labeled two types of morphologically distinct fibers in layer I as well as a smaller number of axons in layers II and III. Layer II injections labeled descending axons that produced a dense plexus of terminal fibers in layers I–III of both AI and adjacent auditory fields. Injections in layer III also labeled a dense plexus of axon collaterals at the junction of layers V and VI and labeled patches of terminal fibers in both AI and adjacent auditory fields. These were densest in layers I–III but usually extended into layers IV and V as well. The patches were partly formed by axon collaterals of layer III pyramidal cells that traveled for over 4 mm in the gray matter. Injections confined to layer IV labeled axons in all layers of the cortex but none of these axons appeared to reach the white matter. The axons spread laterally in layer IV and up into the superficial layers and ramified especially layer I. Injections in layers V and VI labeled axons in all layers of the cortex but these were densest in the deep layers where labeling was fairly homogeneous. In the upper layers the labeling was arranged in semi-discrete patches. Large injections involving layers I–III were studied in tangential sections. Between 3 and 8 patches of terminal labeling were observed in AI and these were mainly arranged in a band with its long axis aligned approximately in the dorsoventral direction. However dense patches of terminal labeling also occurred both anterior and posterior to the injection site. In selected experiments portions of the tonotopic map in AI were mapped by single unit recording and subsequently the map was related to patches of anterogradely labeled fibers that surrounded injections of PHA-L. Rows of dorsoventrally oriented patches were among cells with a similar best frequency to those in the injection site. However patches located anterior or posterior to the injection site were among cells with higher or lower best frequencies. Two injections of PHA-L close together produce different patterns of labeling. One of the injections usually produces one or more patches that has no correlate among the patches of fibers labeled by the adjacent injection. This is clearest when one of the injections is made with biotinylated PHA-L that can be visualized directly without the use of primary antibodies. Thus the intrinsic connections of AI arising from nearby cylinders of neurons are not homogenous and clusters of cells can be identified by their unique pattern of connections within AI.

Notes: Summary The aim of the research program of which the present work is a part is to understand the neural mechanisms involved in motor learning and memory. One of the mechanisms postulated to be involved in this process is the induction of long-term potentiation (LTP) in the motor cortex. LTP can be induced in motor cortical neurons by tetanic stimulation of their afferents from the somatosensory cortex. In the present study, the effects of different stimulating parameters on the induction of LTP were examined, using in-vivo, intracellular recordings from anesthetized cats. The expression of LTP was documented by measuring the amplitude and rise-time of excitatory postsynaptic potentials (EPSPs) before and after tetanic stimulation. The minimal tetanic stimulation capable of systematically inducing LTP was found to consist of a train of stimuli at 50 Hz, 5 s. Shorter trains of stimulation produced only a short-lasting, transient potentiation. In different cells, identical stimulation parameters resulted in different degrees of potentiation of synaptic responses. Following all the stimulation trains examined, EPSP amplitudes were transiently depressed before reaching potentiated levels. The duration of this depression was directly correlated with the duration and the frequency of the tetanic stimulation. In all the cells in which LTP was induced, the variability in the amplitudes of potentiated EPSP was significantly greater than that of control EPSP amplitudes. Hyperpolarization of the postsynaptic cell, during the delivery of the tetanic stimulation, inhibited the induction of LTP. These phenomena are discussed in relation to the postulated mechanisms of LTP induction in the cortex.

Notes: Summary Discharges of gamma motoneurones were recorded from cut filaments of the nerve to the gastrocnemius medialis muscle in the cat decerebrated at an intercollicular level. Gamma motoneurones exhibited a background discharge in the absence of intentional stimulation, or could be made to discharge by continuous, innocuous stimulation of the skin of the heel. The discharges were periodic and regular (low coefficient of variation of interspike intervals), and no correlation was observed between the discharges of pairs of individual gamma efferents. Electrolytic lesion of the ipsilateral pontine and medullary reticular formation in the nucleus subcoeruleus, the nucleus reticularis gigantocellularis or the nucleus reticularis magnocellularis, invariably decreased regularity of discharge and resulted in short term synchrony. Lesions of the peri-aqueductal grey, the nucleus raphe dorsalis or the midline raphe nuclei did not induce synchrony. Surgical lesions in the locus coeruleus caused irregular firing and synchrony only when the lesion extended into the adjacent nucleus subcoeruleus. We conclude that monoaminergic neurones of the nucleus subcoeruleus, or a closely associated tegmental field, with axons descending through the gigantocellularis and magnocellularis fields, are the most likely origin of the bulbospinal control of synchronizing influences on gamma motoneurone discharge.

Notes: Summary Terminal loss and recovery were assessed in the cat dorsal lateral vestibular nucleus (dLVN) following diffuse axonal damage caused by experimental traumatic brain injury. Using sterile technique, anesthetized adult cats received a moderate fluid-percussion traumatic brain injury. After predetermined survival periods of 7–368 days, the animals were perfused and the dLVN prepared for the immunocytochemical visualization of GABAergic puncta/terminals at the light (LM) and electron (EM) microscopic levels. In controls, the Deiters' neuronal somata within the dLVN were encompassed by numerous GABA-immunoreactive puncta/terminals. Within 7 days of injury, axonal damage was seen scattered throughout the dLVN, and associated with this, some neuronal somata demonstrated a dramatic loss of perisomatic GABA-immunoreactive puncta, while other somata appeared unchanged. Ultrastructural examination demonstrated that the loss of immunoreactive puncta observed with LM was directly correlated with the presence of degenerating GABAergic terminals. Overall, these neuronal somata showed a reduction of perisomatic puncta/terminals to values approximately 25% of controls. Over a thirty day posttraumatic course, this pattern of scattered perisomatic puncta/terminal loss persisted, with some puncta/terminal return by 60 days postinjury. During the next six months, a recovery of the immunoreactive puncta/terminals was observed in relation to the deafferented somata, with perisomatic terminal numbers now reaching 75% of control values. Over the 7 to 12 month postinjury period, recovery continued, with virtually complete recovery observed in the later phases of this period. Importantly, throughout this recovery period, there was a consistent correlation between the light and electron microscopic findings. The observed diffuse pattern of terminal loss, followed a prolonged adaptive recovery process, suggests that traumatic injury with its attendant diffuse axonal injury and related diffuse deafferentation creates a unique environment for rather complete and adaptive synaptic recovery. As diffuse axonal injury is a common feature of human traumatic brain injury, we believe that these studies, performed in cat, help explain some of the initial morbidity as well as some of the partial recovery seen in head-injured man.

Notes: Summary The responses of 81 cells from area 17 in paralysed and aneasthetized cats were studied with moving spots and moving bars of different lengths. Tuning curves were measured and plotted as polar-plots. The strongest response of visual cortical cells to a moving bar occurs when the stimulus trajectory crosses the long axis of the receptive field (Hubel and Wiesel 1962). The optimal orientation for a moving and a flashing bar are identical, so that this response-type has been called the orientational component. For a moving spot, however, in most cases the strongest response occurs for motion along the receptive field long axis (axial component). Thus, the axial and orientational components are orthogonal (Wörgötter and Eysel 1989). It is shown that orientational and axial components can display direction selectivity and for short bar stimuli a superposition of the two orthogonal components is demonstrated. Such a superposition in general, resulted in a polar-plot with four peaks 90° apart from each other (four-symmetrical polar-plot). Polar-plots with three or two response peaks were also found; the actual number of response peaks depending on the direction selectivity of the components. In many cells pure axial responses could be elicited with a light spot which stimulates only motion dependent mechanisms. Thus, it was concluded that temporal facilitation is strongly involved in the generation of axial responses. Fourier analysis of polar-plots (SDO-analysis, Wörgötter and Eysel 1987; Wörgötter et al. 1990) was applied to determine the tuning strengths of the different components. In correspondence with the periodicities of a moving oriented stimulus in the visual field, the first harmonic represents directional selectivity, the second orientation selectivity and the fourth harmonic was used to quantify the four-symmetrical superposition effect. It was statistically shown that the strongest superposition (i.e. largest fourth harmonic) occurred for intermediate bar lengths (1–2°). For longer bars only the orientational and for shorter bars predominantly the axial component occurred. In monkey visual cortex (V1, V3) four-symmetrical polar-plots can be obtained even with long stimuli (De Valois et al. 1982; Felleman and Van Essen 1987). Consequentially, we show that a strong fourth order Fourier component occurs. This supports the importance of quantification of higher order symmetries in cortical tuning curves by higher order harmonics in SDO-analysis.

Notes: Summary The profile of integration in a sample of 183 interneurones localized in the subnucleus-γ of the oral nucleus of the spinal trigeminal tract (NVspo-γ) has been analyzed. 134 neurones were tested for inputs from primary afferents of the trigeminal, facial and cervical nerves as well as for inputs from the midbrain and from the cervical spinal cord. The remaining 49 neurones were tested for inputs from the primary afferents and for descending convergence from defined sites within the oro-facial primary projections of the cerebral cortex. It was found that the interneurones, mainly recorded in the dorsal and dorsomedial aspect of the NVspo-γ, receive short latency inputs from the low threshold oral and perioral afferents and longer latency inputs from the high threshold jaw and neck muscle afferents. There was evidence for convergence from the cervical segmental level (29%) and some of the neurones had axon terminals in the superior colliculus. However, the interneurones did not receive a descending tectal input. About 80% of the NVspo-γ interneurones were activated from the orofacial primary projection fields within cytoarchitectonic areas 3a and 3b of the coronal gyrus. This input was topographically organized and the neurones were activated from the same oral and perioral region of the periphery as the cortical region from which the descending projections themselves originated. Minimum latencies indicated a monosynaptic connection. The convergence profile onto the NVspo-γ interneurones appeared unique as compared with interneurones located in the intertrigeminal area. Aspects of the possible functional roles of the NVspo-γ neurones are discussed in relation to ongoing oro-facial (“masticatory”) movements. The properties of a selected sample of NVspo-γ interneurones, which were antidromically activated from the digastric subnucleus of the trigeminal motor nucleus, are reported in a companion paper (Olsson and Westberg 1991).

Notes: Summary (1) Vestibulo-ocular reflex excitation of the six extraocular muscles was studied by recording their electromyographic activity in decerebrate cats during oscillations about horizontal and vertical axes, at frequencies from 0.07 to 4 Hz. Animals were oriented in many different positions and rotated about axes that lay in the horizontal, frontal, or sagittal planes defined by our coordinate system. (2) The strengths of modulation (gains) of the responses of all extraocular muscles were a sinusoidal function of the orientation of the rotation axis within a coordinate plane, and this function was nearly independent of rotation frequency. (3) The responses were used to determine an axis of maximal excitation for each of the extraocular muscles by the vestibulo-ocular reflex. Antagonistic muscle pairs were found to have best axes in nearly opposite directions, confirming their operation as pairs. (4) Excitation of the medial and lateral rectus could be explained by input from the paired horizontal semicircular canals, with essentially no convergent input from vertical canals. (5) Excitation of the vertical rectus and oblique muscles could be explained by convergent inputs from the vertical canals with little or no horizontal canal input.

Notes: Summary The effect of claustrum (CL) stimulation on the spontaneous unitary activity of ipsi and contralateral frontal oculomotor neurons, was studied in chloralose-anaesthetized cats. A total of 205 units was bilaterally recorded in the medial oculomotor area, homologous of the primate “frontal eye fields” 127 neurons were identified as projecting to the superior colliculus; for 33 of these last units stimulation of the ipsilateral CL provoked an excitatory effect lasting 10–25 ms and appearing with a latency of 5–15 ms; on 8 units the excitatory effect was followed by an inhibition lasting 100–250 ms. Ninety-eight of the 127 neurons were also tested through activation of the contralateral CL: 13 cells showed an excitatory effect lasting 10–35 ms and appearing with a latency of 20–50 ms. In three of the thirteen units the excitatory effect was followed by an inhibition lasting 100–150 ms. Complete section of the corpus callosum abolished the contralateral CL effect, suggesting the existence of a direct claustro-contralateral oculomotor cortex pathway running through the corpus callosum. The results could support the hypothesis that the CL may play a role in the bilateral control of the visuomotor performance.

Notes: Summary In the cat visual cortex, almost all parvalbumin-positive cells are GABAergic, and about 80% of the calbindin D-28K-positive neurons are also GABA-immunoreactive. About 37% of the GABAergic neurons contain parvalbumin and a smaller fraction (about 18%) contains calbindin. Furthermore, parvalbumin and calbindin are localized in two separate neuronal populations in the cat visual cortex, suggesting that two GABAergic populations can be distinguished, one containing parvalbumin and one containing calbindin. Double staining for parvalbumin and neuropeptides (CCK, SRIF and NPY), revealed no double-labeled cells, with the exception of a few SRIF- and parvalbumin-positive neurons. These results show that cortical GABAergic cells can be differentiated on basis of their calcium binding protein and neuropeptide immunoreactivity.

Notes: Summary 1. The effect of stimulating the contralateral pyramid has been investigated with intracellular recording from 128 long propriospinal neurones (long PNs) in the C3-Th1 segments of the cat. Long PNs were identified by the antidromic activation from the Th13 segment. They were located in laminae VII–VIII of Rexed. Single pyramidal stimulation evoked monosynaptic EPSPs in 15/40 of the long PNs in cats with intact pyramid. In 15 other long PNs, a train of three to four pyramidal stimuli evoked EPSPs with latencies indicating a minimal disynaptic linkage. The remaining 25% of the long PNs lacked mono- or disynaptic pyramidal EPSPs. In a few cases longer latency excitation was observed. 2. The location of the intercalated neurones which mediate the disynaptic pyramidal EPSPs was investigated by making four different lesions of the corticofugal fibres: 1) at the border of the C5 and C6 segments, 2) at the border of the C2 and C3 segments, 3) at the caudal part of the pyramid; three mm rostral to the decussation and 4) at the level of the trapezoid body. Stimulation of the corticofugal fibres was made either rostral to lesion 3 (rPyr) in order to activate neurones in a cortico-bulbospinal pathway or caudal to lesion 3 (cPyr) to activate neurones in a corticospinal pathway. In the former case, in one experiment, stimulation was made in the pyramid between lesions 3 and 4 (double pyramidal lesion). In case of cPyr stimulation, lesions 1 and 2 were added sequentially in order to investigate if the corticospinal excitation was mediated via C3–C4 PNs. All lesions were made mechanically, except lesion 2 which in some of the experiments was performed by reversible cooling. 3. Stimulation in the pyramid rostral to lesion 3 and in between lesions 3 and 4 evoked disynaptic EPSPs in the long PNs, which shows that they were mediated via reticulospinal neurones. Stimulation in cPyr after lesion 3 elicited disynaptic EPSPs, which remained after lesion 1 but were abolished after adding lesion 2. It is concluded that the disynaptic cPyr EPSPs were mediated via intercalated neurones in the C3–C4 segments. 4. When the disynaptic cPyr EPSP was conditioned with a single volley in nucleus ruber and/or in tectum, it was markedly facilitated, especially when the conditioned volley was applied simultaneously with the effective cPyr volley. The results show that the intercalated neurones in the C3–C4 segments receive monosynaptic convergence from cortico-, rubro- and tectospinal] fibres. Stimulation in the lateral reticular nucleus (LRN) evoked monosynaptic EPSPs. These EPSPs had similar latencies and shapes as those previously recorded in forelimb motoneurones and which have been shown to be due to activation of ascending branches of the C3–C4 PNs. This finding in addition to the striking similarity of the descending input pattern of long PNs as compared to the forelimb motoneurones strongly suggest that short C3–C4 PNs project both to long PNs as well as to forelimb motoneurones. 5. Spatial facilitation of disynaptic EPSPs in long PNs was also observed between rPyr volleys and tectal volleys. The results suggest that common reticulospinal neurones which project to the long PNs receive monosynaptic convergence from corticofugal and tectofugal fibres but in some of the reticulospinal neurones the main input is cortical and in others tectal. Monosynaptic EPSPs were evoked from the medial part of the reticular formation, from 2 mm caudal to 6 mm rostral of the obex level. These EPSPs were presumably due to direct activation of reticulospinal neurones. 6. Convergence of disynaptic excitation mediated by cortico-propriospinal and cortico-reticulospinal routes was observed in about 12% of the long PNs. Convergence of monosynaptic corticospinal and disynaptic corticoreticulospinal and/or cortico-propriospinal input was observed in about 15% of the long PNs. 7. The role of the monosynaptic pyramidal input and disynaptic corticoreticulospinal and cortico-propriospinal (mediated by short C3–C4 PNs) inputs to long PNs is discussed in relation to postural control during movements of head and forelimb.

Notes: Summary Anatomical texts describe the neck musculature without measurements of muscle locations or quantitative estimates of pulling actions (torques). This study is based on measurements in stereotaxic coordinates of cat neck muscle origins and insertions, and neck intervertebral rotation axes. Torque vectors in three dimensions were calculated for 14 pairs of dorsal and ventral muscles that insert on the skull or first cervical vertebra. Predicted torque vectors were in general agreement with qualitative statements in the literature. Biventer cervicis and the rectus capitis major, medius, and minor muscles act mainly to raise the head, and longus capitis acts almost exclusively to lower the head. Longissimus capitis, sternomastoid, and cleidomastoid act mainly to roll the head. Complexus acts about equally to raise the head and roll it. Splenius and occipitoscapularis have torque in all three coordinate directions. Torques were altered by changing the pitch of the head with respect to the neck. The calculated neck muscle torques did not correspond to previously reported directions of neck muscle excitation during the vestibulocollic reflex. The neck musculature appears to be a complex, multidimensional system that presents interesting problems in motor control.

Notes: Summary The receptive field centre of cells in the dorsal lateral geniculate nucleus were mapped as iso-sensitivity contours. 94% of the cells were found to have elliptical centres, and analysis of the major axis orientation showed that 29% and 59% of units had their major axis oriented within ± 20° of the radial and horizontal directions, respectively. The data for Y-cells showed a greater dispersion in their orientation biases (R = 0.57) compared with X-cells (R = 0.79). Nevertheless, a horizontal orientation bias was found in both classes of cells: 47% of Y-cells and 73% of X-cells. In addition, an examination of the major axis orientations was undertaken for cells with receptive field centres located along the radial direction of 35° below the horizontal meridian. In this 35° Radial Group a horizontal bias was also confirmed. Analysis of the dispersion of major axis orientations with eccentricity from the area centralis showed a statistically significant decrease in scatter and, hence, indicated an increase in the horizontal bias with eccentricity.

Notes: Summary In the present study we recorded the activity of single neurons in the forelimb area of red nucleus (RN) during performance of three step-tracking tasks designed to dissociate the coding of stimulus and response variables in the discharge of recorded neurons. In two of these tasks, the standard and stimulus-reversal arm tasks, elbow flexion and extension were elicited by different stimuli enabling us to distinguish activity correlated with the forelimb response from the stimulus eliciting it. The third task (neck task) allowed us to determine whether neuronal modulation was related to an unconditioned orienting response that occurred concurrently with the forelimb response. We have previously reported that these three tasks separate neurons in MCx whose modulation precedes the response (lead cells) into three distinct classes in which task-related activity either is correlated with the direction of the forelimb response, correlated with the stimulus, or not correlated with either (Martin and Ghez 1985). All lead cells, however, remained timed to the stimulus rather than to the response. The present results show that RN lead cells can be subdivided into the same three classes as those in MCx and their discharge was also contingent on the subsequent production of a behavioral response. (1) Force-direction neurons (35%; n = 16) showed changes in activity correlated with the production of forearm force in a particular direction suggesting that they could participate in selecting the appropriate forelimb response. The onset of task-related modulation of activity was better timed to the response, in contrast to force-direction neurons in MCx, which were better timed to the stimulus. (2) Stimulus-direction neurons (18%; n = 8) modulated their activity in relation to a particular stimulus evoking either flexor or extensor responses and during neck task performance. These neurons could be involved in processing stimulus information or in the production of neck torque. The task-related discharge of these lead cells was better timed to the stimulus than to either the forelimb or the neck response. (3) Nondirectional neurons (47%; n = 21) modulated their activity during all tasks examined. Their discharge did not correlate with any specific feature of the stimulus or response, and as a group, was better timed to the stimulus than to the response. Nondirectional neurons may participate in some aspect of motor preparation. To determine the relative contributions of RN and MCx lead cells to response initiation, we compared the amount of response latency variance that could be explained by variation in the latency of the unit modulation to the stimulus for the present data and the data in the earlier MCx study (Martin and Ghez 1985). Between 38% and 53% of response latency variance (for trials examined during performance of the standard arm and stimulus reversal tasks) was accounted for by the latency variations of RN force direction neurons; in contrast, 8% and 11% for MCx force-direction neurons. Variations in timing of stimulus-direction neurons in both RN and MCx account for less than 10% of response latency variance. Our findings suggest that, in the tasks examined, RN force-direction neurons play a more direct role than MCx force-direction neurons in initiating and selecting responses to stimuli. We hypothesized that this subcortical control reflects the high degree of stereotypy of the motor response examined.

Notes: Summary Immunocytochemical methods have been combined with serial thin section analysis to study the synaptic organization of serotonin (5-HT) and tyrosine hydroxylase (TH) immunoreactive terminals in the ventral posterior nucleus of the cat and monkey thalamus. One hundred 5-HT immunoreactive terminals from the cat and approximately forty 5-HT and TH immunoreactive terminals from the monkey were selected for analysis in serial thin sections. Only 7–10% of the immunoreactive terminals could be revealed to form conventional synaptic contacts. Most of these could be identified as the asymmetrical type. Dendritic shafts belonging to relay neurons were the major targets of these monoamine immunoreactive terminals. The remainder made intimate membrane associations with relay cell dendrites and somata or with presynaptic dendrites of interneurons, but no overt membrane specializations could be detected. The present results suggest that the modulation of thalamocortical relay function by brainstem monoamine pathways in the somatosensory thalamus may occur by release of transmitters at atypical contact sites.

Notes: Summary A functionally meaningful vestibular-neck interaction, such as it has been demonstrated for postural reflexes and self-motion perception, requires the spatial and temporal response characteristics of vestibular and neck signals to be similar. We investigated the spatial coding in neurons of the external cuneate nucleus (ECN) with natural neck and vestibular stimulations, and compared them to that of neurons in the descending and medial vestibular nuclei (DVN and MVN, respectively) obtained with vestibular stimulation. Neurons were recorded extracellularly in chronically prepared cats held under light barbiturate anesthesia. Neck stimulation was performed by sinusoidally rotating the animals' trunk relative to the earth-fixed head in six different vertical planes and in the horizontal plane. Vestibular stimulation was elicited by whole-body rotations in the corresponding planes. During neck stimulation in the vertical planes, most ECN neurons showed an approximately sinusoidal discharge modulation about resting rate, which became maximal during rotation in a specific plane. Off this plane, the response declined along a cosine function and reached zero in the orthogonal plane. The majority of these ECN neurons also responded to horizontal neck rotation; the resulting “optimal” direction of rotation in three-dimensional space varied considerably among the neurons. Yet, there was a certain preference; the majority of these ECN neurons fired maximally if trunk rotation in the yaw plane stretched the neck on the ipsilateral side, if roll brought the contralateral shoulder closer to the head, and if pitch brought the back closer to the occiput. A minority of ECN neurons showed more complex response patterns which could not be described by a single, optimal direction. About one third of the neck-sensitive ECN neurons tested showed weak responses during whole body rotation, which might stem from a weak vestibular input to this nucleus. In the DVN and MVN, the optimal direction in three-dimensional space with vestibular stimulation typically had a cosine-like spatial tuning. The spatial distribution of these directions clearly differed from that of neck-sensitive neurons in the ECN. We therefore assume that a further processing of the two input signals takes place at later stages in the CNS (e.g., in the vestibulo-cerebellum) in order to yield a functionally useful vestibular-neck interaction.

Notes: Summary Single unit recordings from two alert cats were used in an attempt to further elucidate the function of the lateral mesencephalic tegmental region (LTR), a part of the mesencephalon forming a link between the superior colliculus and the lower brain stem. A total of 155 units recorded from the LTR were tested with visual, vestibular and acoustic stimuli. Of these, 54 cells (36%) were characterized as either visually (n=33) or vestibularly (n=21) responsive and an additional 13 cells were driven by complex acoustic stimuli. Visually responsive cells typically were directionally selective with large, mainly contralateral receptive fields. Vestibularly responsive cells were modulated by stimulation of either the horizontal canals (yaw stimulation; n = 16) or of both pairs of vertical canals (pitch stimulation; n=5). About half of the cells with activity modulated by rotation about the yaw axis increased discharge during ipsiversive (Type I), the other half during contraversive rotation (Type II). Of the 5 cells with activity modulated by pitch stimulation, 4 preferred the nose-down and only 1 the nose-up direction. Although the discharge of units responsive to yaw stimulation was roughly in phase with head velocity (mean phase lag with respect to head velocity: 10.6 deg), none of the vestibular cells had activity correlated with eye position, eye velocity or movement of visual stimuli. Our observations suggest that the LTR might introduce visual and vestibular signals into the tecto-facial pathway which may be used to adjust the size of pinna movements with respect to the size of ongoing head- or body movements.

Notes: Summary The relative proportions of synapses made by retinal and extraretinal terminals on interneurons and relay cells in lamina A of the dorsal lateral geniculate nucleus (LGN) of the cat were estimated quantitatively in a sample of 4003 synapses. Processes of interneurons or relay cells were identified by presence or absence of GABA immunoreactivity, respectively, in thin sections treated with post-embedding anti-GABA immunogold. On the basis of ultrastructural features, synaptic terminals were interpreted as belonging to retinal axons, cortical axons or axon collaterals of relay cells. GABAergic terminals were positively identified by being immunoreactive. GABA(-) terminals with heterogeneous and poorly defined characteristics, which could not be identified in the above classes, were grouped together in an “undetermined” category. Among the total synaptic inputs to interneurons, the following relative percentages of synapses from different terminals were obtained: retinal 25%, cortical 37%, GABAergic 26%, axon collaterals 2%, undetermined 6%. The vast majority of retinal terminals synapse on dendritic appendages of interneurons rather than on their dendritic trunks (about 20∶1). By contrast, the majority of cortical terminals synapse on dendrites rather than on dendritic appendages (about 5∶1). Virtually all axon-collaterals synapses were established on dendritic appendages. 17% of the dendritic profiles of interneurons contain synaptic vesicles; many of these profiles were seen in postsynaptic relation to cortical axons and in presynaptic relation with relay dendrites. Given the extensive electrotonic lengths of these cells observed by others, and the expected high electric resistance of the slender stalks that are known to connect the dendritic appendages to interneurons, these results suggest that microcircuits involving the interneuronal dendritic appendages with dendrites of relay cells are under predominantly retinal control. The microcircuits established by presynaptic dendritic trunks with relay dendrites, are under predominantly cortical control. The axonal (spiking) output of interneurons would be under control of the few retinal synapses on proximal dendrites of these cells. Among the total synaptic inputs to relay cells, the following relative percentages of different synapses were obtained: retinal 12%, cortical 58%, GABAergic 24%, axon collaterals 0.3%, undetermined 5%. Relay cells receive twice the number of cortical synapses than interneurons, suggesting that direct cortical excitatory influences on relay cells are more preponderant than cortico-interneuron mediated inhibition on these cells. The observed proportions of dendritic profiles of relay cells and interneurons (80% and 20%, respectively) in the geniculate neuropil are similar to the known proportions of somata of both types of cells in the A-laminae. This suggests a similarity in the average dendritic branching of relay cells and interneurons.

Notes: Summary The utriculo-ocular pathway was examined in decerebrated and anesthetized cats, in which all the vestibular afferents in the labyrinth, except for those innervating the utricular (UT) macula, had been transected. The UT nerve was stimulated with tungsten electrodes which were insulated except for 200 μm at the tips. Stimulation of the UT nerve evoked a small negative (N1) potential in the vestibular nuclei, with a threshold (N1T) less than 25 μA. The stimulus evoked disynaptic EPSPs in ipsilateral abducens (AB) motoneurons. The threshold and latency of the excitatory postsynaptic potentials (EPSPs) was 1.3 × N1T and 1.2 ms, respectively, in accordance with the data of Schwindt et al. (1973). On the other hand, EPSPs with a clear rising phase and short latency, suggesting the existence of a disynaptic pathway, were never observed in any contralateral troch-lear (TR) motoneurons, even when triple shocks at intensities of up to 4 × N1T were applied. This stimulus strength was strong enough to activate the UT nerve. Thus it seems very likely that a disynaptic pathway from the UT nerve to contralateral TR motoneurons, is absent or very poorly organized.

Notes: Summary Single unit activity of 355 cells was recorded in the auditory thalamus of anesthetized cats before, during, and after the inactivation by cooling of the ipsilateral primary auditory cortex (AI). Most of the units (n = 288) showed similar functional characteristics of firing before and after the cryogenic blockade of AI. The spontaneous firing rate remained unchanged by cooling in 20% of the units and decreased in the majority of them (60%). In some regions, i.e. dorsal division of the medial geniculate body (MGB), lateral part of the posterior group of the thalamus, and auditory sector of the reticular nucleus of the thalamus, the maximum firing rate evoked by white noise bursts was generally affected by cooling in the same direction and to the same extent as the spontaneous activity. Units in the ventral division of MGB showed a characteristic increase of signal-to-noise ratio during cortical cooling. The corticofugal modulation led to the appearance or disappearance of the best frequency of tuning in 51 units and changed it by more than 0.5 octave in 34 units. The bandwidths of different response patterns to pure tones stimulation were used to define a set of functional properties. During cryogenic blockade of AI, two cortically modulated sub-populations of units were usually distinguished that exhibited changes for a given functional property. The complexity and diversity of the effects of cortical inactivation suggest that the corticothalamic projection may be the support for selective operations such as an adaptive filtering of the incoming acoustic signal at the thalamic level adjusted as a function of cortical activity.

Notes: Summary The goal of this study was to analyze the architecture of the cat biceps femoris (BF), a multifunctional hamstring muscle, and to evaluate the relationships between muscle architecture, limb position, and muscle function during natural movement. The BF muscle consists of three neuromuscular compartments: anterior (BFa), middle (BFm) and posterior (BFp). Each compartment is innervated by a separate nerve branch. Nerve branch stimulation and 2-dimensional surface EMG recordings showed that individual compartment territories were discrete and non-overlapping with welldefined borders. Comparisons of the three compartments revealed consistent differences in architecture, relationship to the skeleton, and function. The BFa crossed only the hip joint and appears to function as a pure hip extensor. The BFm had equal lever arm lengths to the hip and knee joints, appears to function as a hip extensor, and may contribute to knee flexion or femoral rotation. The BFp had a greater lever arm to the knee, functions as a knee flexor, and may contribute to hip extension, femoral rotation or ankle extension. Measurements of individual fascicles from the three compartments revealed a surprising range of lengths, 3.3–12.0 cm. Microdissection of gold-stained tissue showed that fascicles from all compartments were comprised of interdigitated, short fibers (range: 0.6–5.0 cm; average 2.14 cm) arranged in-series in fascicles, running parallel to the origin-insertion axis of each muscle compartment. In regions of fiber interdigitation, the fiber endings were round and tapered (taper lengths: 1–11 mm) although flat, tapering endings like ribbons were occasionally found. As hip and knee joint angles were varied over physiological ranges corresponding to minimal to maximal muscle length, fascicles of the three compartments changed length disproportionately. Long BFa fascicles maximally lengthened 10–18%, consistent with in vivo length measures during treadmill locomotion. However, the long BFp fascicles lengthened 25–45%, and the relatively short fascicles near the BFm/BFp border maximally lengthened 45–53%. How do these unexpectedly large length changes affect sarcomere lengths? Using laser diffraction to measure sarcomeres, static fascicle and sarcomere lengths were compared in muscles that went into rigor mortis after fixing the hip and knee joint angles. Sarcomeres within the short BFm/BFp and long BFp fascicles consistently lengthened proportionately less than the whole fascicle. It remains to be determined how and where the fascicle length changes are dissipated in the connective tissue between the interdigitated muscle fibers and whether such a series-compliance operates during the large excursions over which this muscle normally works.

Notes: Summary Similarities between the muscle synergies associated with the flexion reflex and locomotion in reduced preparations have suggested that spinal circuits subserving these two motor tasks might share common interneurons. To test this hypothesis in functionally complex muscles, we studied the interaction between low-threshold cutaneous afferents and the locomotor central pattern generator (CPG) during treadmill locomotion in awake, intact cats. Electrical stimuli were delivered via implanted nerve cuff electrodes at all phases of locomotion, and EMGs were recorded from fourteen intramuscular subregions in eight bifunctional thigh muscles (adductor femoris, biceps femoris, caudofemoralis, gracilis, semimembranosus, semitendinosus, tensor fasciae latae, and tenuissimus). In addition, the EMG patterns recorded during locomotion were compared with those recorded during two other centrally driven rhythmical behaviors, scratching and paw shaking, to determine whether the functional relationships among these intramuscular subregions were fixed or task dependent. Four of the five broad, bifunctional muscles studied (biceps femoris, gracilis, semimembranosus, and tensor fasciae latae) had functional subunits that could be differentially activated in one or more of the three movements studied; adductor femoris was consistently uniformly activated despite its distributed skeletal attachments. The pattern of recruitment of the intramuscular functional subunits was movement-specific. The locomotor CPG and cutaneous reflex pathways both similarly subdivided some bifunctional muscles, but not others, into intramuscular subregions. The results of the present study confirm that some combinations of muscle subregions and cutaneous nerves constitute simple reciprocal categories of flexors and extensors, as described originally by Sherrington (1910). “Typical” low threshold excitatory or inhibitory reflex responses were produced in muscles or muscle subregions that were recruited as “net” flexors of extensors, respectively. However, muscles with complex activation patterns during walking often had very individualized, complex reflex responses during locomotion that did not conform to the background locomotion synergies. All of the reflex responses observed were mediated by low threshold cutaneous afferents. These data indicate that there are multiple, low threshold, excitatory and inhibitory cutaneous reflex pathways that have highly specialized connections with flexor and extensor muscles and even their intramuscular subregions. It is also clear that the premotoneuronal circuits mediating these cutaneous reflex effects are not necessarily synonymous with those of the locomotor CPG. These two systems do interact powerfully, however, suggesting some convergence. The nature of the convergence between the CPG and the many independent subsets of spinal interneurons mediating cutaneous reflexes is specialized and muscle subregion-specific.

Notes: Summary 1.The somatic location and axonal projections of inhibitory vestibular nucleus neurons activated by the horizontal semicircular canal nerve (HCN) were studied in anesthetized cats. Cats were anesthetized with ketamine hydrochloride and pentobarbital sodium. 2.Intracellular recordings were obtained from 11 neck extensor motoneurons which were identified by antidromic activation from the dosai rami (DR) in the C1 segment. Stimulation of the ipsilateral (i-) HCN and the ipsilateral abducens (AB) nucleus evoked IPSPs in the motoneurons. These IPSPs were fully or partially occluded when they were evoked simultaneously. 3. Intracellular recordings were obtained from 8 AB motoneurons. Stimulation of the i-HCN and the i-C1DR motoneuron pool evoked IPSPs in the AB motoneurons. These IPSPs were also partially occluded when they were evoked simultaneously, which implied that some HCN-activated neurons inhibit both i-AB motoneurons and ipsilateral neck motoneurons. 4. Unit activity was extracellularly recorded from 30 vestibular neurons that were activated monosynaptically by i-HCN stimulation. Their axonal projections were determined by stimulating the i-AB nucleus and the i-C1DR motoneuron pool. Eight neurons were activated by both stimuli, and were termed vestibulooculo-collic (VOC) neurons. Their axonal branching was examined by means of local stimulation in and around the i-AB nucleus and the i-C1DR motoneuron pool. Eighteen neurons were antidromically activated from the i-C1DR motoneuron pool but not from the i-AB nucleus. These were termed vestibulo-collic (VC) neurons. Four neurons were activated from the i-AB nucleus but not from the ventral funiculus in the C1 segment, and were termed vestibulo-ocular (VO) neurons. The HCN-activated inhibitory neurons were mostly localized in the rostroventral part of the medial vestibular nucleus. 5. Horseradish peroxidase (HRP) was injected iontophoretically into descending axons of 2 HCN-activated inhibitory VOC neurons which were identified by stimulation of the i-HCN and the i-AB nucleus. Axon collaterals were ramified from a stem axon in the ventral funiculus, and entered the gray matter and spread in the laminae VIII and IX. Terminal boutons were distributed over the medial and the ventromedial parts of the vental horn in the C1 segment.

Notes: Summary Somatostatin-like immunoreactivity was localized in nerve cell bodies and nerve terminals in the cat coeliac ganglion. Two types of somatostatin-immunoreactive cell bodies were revealed, the first being large (diameter 35 μm), numerous and weakly labelled, where—as the second was considerably smaller (diameter 10.4 μm), sparsely distributed and heavily stained. The immunoreactive nerve terminals were in synaptic contact with many immunonegative large neurons and dendrites. However, in a few cases, somatostatin-immunoreactive nerve terminals could also be observed on the surface of lightly stained neurons. Transection of vagal or mesenteric nerve failed to affect the distribution or density of somatostatin-like immunoreactive nerve terminals. These results demonstrate the existence of a synaptic input to the principal neurons of the coeliac ganglion of the cat by somatostatin-containing nerve terminals and suggest that this peptide may act as a neuromodulator or neurotransmitter. It is proposed that somatostatin-positive neurons provide intrinsic projections to other somatostatin-positive and to somatostatin-negative neurons throughout the coeliac ganglion, thereby creating a complex interneuronal system.

Notes: Summary Axonal tracing techniques were used in combination with immunohistochemistry to examine the distribution of neuropeptides in afferent pathways from the uterine cervix of the cat. Primary afferent neurons innervating the uterine cervix were identified by axonal transport of the dye, fast blue, injected into the cervix. Fifteen to twenty-five days after the injection, dorsal root ganglia (L1–S3) were removed and incubated for 48–72 h in culture medium containing colchicine to increase the levels of peptides. Calcitonin gene-related peptide (CGRP), cholecystokinin (CCK), leucine-enkephalin (LENK), somatostatin, substance P and vasoactive intenstinal polypeptide (VIP) were identified by use of indirect immunohistochemical techniques. Eighty-four percent of uterine cervix afferent neurons were identified in the sacral dorsal root ganglia (S1–S3), and 16% in the middle lumbar dorsal root ganglia (L3–L4). In sacral dorsal root ganglia, VIP was present in the highest percentage of dye-labeled cells (71%), CGRP in 42%, and substance P in 18% of the cells. CCK and LENK were present in 13% of the cells. In lumbar dorsal root ganglia, CGRP (51%) was most prominent peptide followed by VIP (34%), substance P (28%), LENK (17%) and CCK (13%). Somatostatin was present in the ganglia but did not occur in dye-labeled neurons. In conclusion, the uterine cervix of the cat receives a prominent VIP-and CGRP-containing afferent innervation. The percentage of neurons containing VIP is three to five times higher than the percentage of these neurons in afferent pathways to other pelvic organs. These observations coupled with the results of physiological studies suggest that VIP is an important transmitter in afferent pathways from the cervix.

Notes: Summary The distribution of nerve growth factor receptor (NGF receptor)-like immunoreactivity in pulps of developing primary and mature permanent cat canine teeth was examined, by use of a monoclonal antibody against NGF receptor detected by fluorescence immunohistochemistry and pre-embedding immunocytochemical light- and electron microscopy. Both primary and permanent pulps contained a vast number of NGF receptor-like immunoreactive nerves. Immunolabelling appeared to be localized both to axons and Schwann cells. In addition, many blood vessel walls in immature primary tooth pulps showed NGF receptor-like immunoreactivity, in contrast to permanent pulps where blood vessels rarely were NGF receptor-immunoreactive. Double-labelling immunofluorescence experiments revealed that in the permanent pulp a majority of the NGF receptor-positive nerves also showed calcitonin gene-related peptide (CGRP)-like immunoreactivity, and many showed substance P-like immunoreactivity. However, nerve fibers with neuropeptide Y-like immunoreactivity lacked NGF receptor-like immunoreactivity. In developing primary tooth pulps fewer NGF receptor-positive nerves were CGRP-like immunoreactive or substance P-like immunoreactive, as compared to the permanent pulp. Neuropeptide Y-like immunoreactive nerve fibers were not detected in the primary tooth pulp. The results suggest a role for nerve growth factor in both developing and mature sensory nerves of the tooth pulp.

Notes: Summary We have examined the distribution and size of nicotinamide adenine dinucleotide phosphate (NADPH) diaphorase reactivity in adult and developing cat retinae. From late gestation E (embryonic day) 58 to adulthood, NADPH-diaphorase reactivity was detected in amacrine cells with somata located in the inner nuclear layer (INL) and ganglion cell layer (GCL) and in processes spreading in the middle strata of the inner plexiform layer (IPL). Reactivity was also present in small rounded profiles located in the outer plexiform layer (OPL) and thought to be cone pedicles. The number of NADPH-diaphorase reactive cells present in adult retinae was about 40 000; 75% of these somata were located in the GCL, the remainder in the INL. At birth, however, there was more than double this number of labelled somata (85 000), the total gradually declining to reach adult values by P (postnatal day) 25. This loss of NADPH-diaphorase reactive somata may be partly explained by natural cell death (apoptosis) or by loss of the active diaphorase from the cells. The density distributions of NADPH-diaphorase reactive cells in the INL and GCL of retinal wholemounts reached maxima in regions slightly inferior to the area centralis at all ages studied. The principal topographical difference between adult and developing retinae was that the density gradient of NADPH-diaphorase reactive cells was steeper in adults than at younger ages. During early development, the somal and dendritic field diameters of NADPH-diaphorase reactive cells at the area centralis were about the same size as those in the periphery; by adulthood, cells in the periphery were larger. The change in the somal diameter gradient apparently emerged because of a reduction in somal size of the centrally located cells. The change in the dendritic diameter gradient emerged because of a greater growth of peripheral cells as compared to central cells. We suggest that NADPH-diaphorase may have a role in the formation of synapses in the developing IPL.

Notes: Abstract In this report the state of the art with respect to PVC as pharmaceutical packaging material is described. A general introduction into the applications of PVC is followed by a description of its production process. The metabolic effects of the monomer of PVC, vinyl chloride and of the most commonly used plasticizer diethylhexylphthalate are mentioned. Special attention is given to the pharmaceutical properties of plasticized PVC bags in comparison to other plastics and the environmental aspects of waste PVC disposal. Although there are emotional and political queries regarding the future use of PVC as a (pharmaceutical) packaging material, we conclude that there is no scientific justification for a total or partial ban of PVC. PVC will remain a fact of life as a cheap, versatile, high-performance and well-investigated plastic material for medical and pharmaceutical applications, to be replaced by newer plastics only for certain well-defined indications where the requirements of the plastic to be used are so specific that it will economically and technically be justified to use another polymer. Community and hospital pharmacists have to be prepared for a role in intake of waste plastic disposables, probably against deposit money, in order to fulfil the logistics needed for recycling.

Notes: Summary Horseradish peroxidase (HRP) was used to investigate the motor fiber orientation in the cat's intratemporal facial nerve. When HRP was applied to the zygomatic rami, HRP-labeled fibers were distributed diffusely throughout the labyrinthine and tympanic segments. On the other hand, distal to the chorda tympani entrance, a well-defined topographical orientation was found in the posterolateral aspect of the nerve. When HRP was applied to the buccal rami, topographical orientation was found in the posteromedial area of the distal mastoid segment. When HRP was applied to the posterior auricular rami, topographical orientation was found in the center to the anterior area of the distal mastoid segment. These results indicate that each branch of the facial motor nerve has a topographical orientation in the distal part of the mastoid segment, while nerve fibers are dispersed in the tympanic and labyrinthine segments.

Notes: The properties (squared dimensions, anisotropy, numbers of intra- and intermolecular contacts) of a single five-way cubic lattice chain embedded into an environment (matrix) of chains of the same length n = 50 were evaluated as a function of matrix volume fraction (matrix density) v and intermolecular interaction between the matrix polymer and the minority chain segments, characterized by a parameter φ. No convincing evidence was found for the occurrence of a coil-globule transition in the range of matrix densities (v ≤ 0.7) and repulsive interactions between matrix and minority chain (φ ≤ 0.2) investigated. For moderate attractive interaction (φ ≈ -0.17) a compensation of the chaincompressing action of the matrix and the chain-expanding interaction with the matrix was observed resulting in a zero-dependence of the size and shape of the minority chain on matrix density. It further turned out that there are fixed relations among the various size and shape data irrespective of the specific combination of matrix density and thermodynamic interaction by which a particular polymer dimension is produced. These interrelations are fairly the same as those evaluated for isolated chains the size of which is varied by an intramolecular energy parameter φi.

Notes: New three phases composite materials made of glassbeads as filler, water as liquid dispersed phase and polystyrene as matrix were obtained by polymerization of a water in oil emulsion formed by water dispersed in styrene in which glass beads are added. For this purpose glass beads have to be modified by silanization by a coupling agent 3-(Trimethoxysilyl)propylmethacrylate (TPM) or a silane Octadecyltrichlorosilane (ODMS), in order to prevent the wetting of the glass by water. Only low coverage of the glass surface by the coupling agent (0,05% of TPM) are convenient for the preparation cellular materials having good mechanical properties. At higher coverage ratio, strong hydrophobic glass beads are obtained which destabilize the water / styrene emulsion and lead to macroporous products. Study of the rheology of the filled emulsion appears to be the more simple and more sensitive method to determine the level of wettability of the glass bead by the emulsion which is the most significant parameter for the preparation of such three phases composite materials. Composite materials made of glass beads, air and polystyrene are simply obtained by evaporation of water under vacuum.

Notes: To test the molecular parameters concerning gas sorption in polymers, the concentration of CO2, N2O, CO, N2, CH4 and the noble gases Ne, He in glassy poly(butylene terephthalate) films (PBTP) has been studied gravimetrically with a recording microbalance at 25°C. The sorption isotherms exhibit downward curvature to the pressure axis. As neither solubility nor adsorption can explain the experimental results, analysis was carried out based on the dual-sorption model: gas dissolution and microvoid filling are considered as independent sorption mechanisms. The parameters of the dual-sorption model for the mentioned penetrants are determined. The results indicate that for parameter correlation the Lennard-Jones potential parameters give a rough idea, but size exclusion of gases in small diameter microvoids is proposed and special chemical interactions must be considered.

Notes: Die ringöffnende metathetische Polymerisation (ROMP) von 5-Cyano-2-norbornen wurde unter Einsatz von Wolframhexachlorid, Wolframoxidterachlorid, Bis(dichloralkoxo)wolframtetrachlorid und Bis(dichloralkoxo)wolframoxiddichlorid als Übergangsmetallkomponente untersucht. Als Cokatalysatoren dienten Methylaluminoxan, Diethylaluminiumethoxid, Tetraisobutyldialuminoxan und Tetrabutylzinn. Als Lösungsmittel wurden Toluol, Chlorbenzol und Dichlormethan verwendet. Die Konzentration der Wolframkomponente lag im Bereich 5 × 10-4 - 5 × 10-3 mol/l. Unter den geprüften Katalysatoren erwies sich Wolframhexachlorid in Verbindung mit Diethylalumiumethoxid als der geeignetste. Mit diesem System verlief die Polymerisation auch bei großen Monomer/Wolfram-Verhältnissen (10200 :1) hochselektiv und führte zu großen Umsätzen (≥82%).

Notes: The dependence of dilution on the chain propagation and termination rate constants was investigated in the polymerization of ethyl acrylate in benzene solution at 50°C, with the rotating sector method. The errors of the above rate constants were determined and, by our method applied to decrease these errors, the errors of the propagation rate constant was reduced to its half value. By the application of our earlier results in polymerization kinetics, we found that in this system the chain propagation step is exclusively responsible for the solvent effects observed. Our experimental results can be quantitatively described in terms of the hot redical theory.

Notes: Low molecular weight amine-terminated monomaleimide prepolymers containing 1,3,5-triazine groups as well as ether linkages were synthesized by reacting benzophenone tetracarboxylic dianhydride, diamines having 1,3,5-triazine group and maleic anhydride. These reactive prepolymers are soluble in low boiling solvents such as chloroform, tetrahydrofuran etc. They were characterized by elemental analyses, IR and NMR spectroscopy, vapour pressure osmometry, and viscosity. On heating at 180-190°C these prepolymers undergo simultaneous chain extension by Michael addition reaction and crosslinking by mutual reaction between their amine-terminated and maleimide-terminated ends. The cured polymers are thermostable and the thermal behaviour was studied by TGA, DTA, and isothermal aging. Laminates fabricated using these prepolymers and carbon fiber as reinforcing agent were evaluated by their flexural strength and interlaminar shear strength.

Notes: Aniline/benzylamine-modified epoxy resins with different molecular weights, which contain tertiary amines in the middle of the polymer chain, were synthesized by the reaction of aniline/benzylamine with epoxy resin at various molar ratios. The resulting aniline/benzylamine-modified epoxy resins were reacted with diethylamine and subsequently reacted with 2-ethylhexanol-blocked toluene diisocyanate to obtain thermally crosslinkable resins which contain tertiary amines at the end and in the middle of the polymer chain. These resins were partially neutralixed with acetic acid to give thermally crosslinkable cationic resins. The resulting cationic resins were dissolved in suitable solvents and mixed with deionized water to form various emulsions. The emulsion and electrodeposition properties of these resins were studied in some detail to compare the properties of these cationic resins. The results show that the deposition yields and throwing power of the emulsions prepared from benzylaminemodified epoxy resins are higher than those of the emulsions prepared from anilinemodified epoxy resins. The emulsion having proper pH values can give a high throwing power. High throwing power is the characteristic property of these modified cationic resins. Factors determining the throwing power and deposition yield of the emulsions were also investigated.

Notes: Aryl acrylic acids, e. g. furyl acrylic acid or thienyl acrylic acid are readily formed by the Knoevenagel condensation reaction of arylcarbaldehydes and malonic acid in pyridine. Esterification of these acids with methanol/sulfuric acid gives the corresponding aryl acrylic acid methyl esters in good yields. In methanolic solution these methyl esters isomerize upon irradiation (λ 280 nm). No photodimerization was observed. Kinetic data are given.

Notes: Divers matériaux composites à base de peuplier rétifié ou naturel et de résine polyester insaturée ont été préparés par moulage. L'influence de la granulométrie de la charge a été étudiée sur quelques propriétés physico-chimiques (densité, reprise d'humidité, dureté) ou mécaniques des matériaux obtenus. La densité et la reprise de masse en milieu humide sont toujours plus faibles si la charge est traitée thermiquement sous atmosphère inerte. Par contre, la dureté des composites issus du peuplier naturel est plus importante. Les propriétés mécaniques sont inférieures si la charge est rétifitée.Si la charge lignocellulosique est traitée thermiquement, il est possible d'optimiser les trois paramètres: densité, reprise d'eau et propriétés mécaniques; la granulométrie optimale du peuplier est ainsi comprise entre 0,75 et 1,5 mm.Les résultats obtenus sont expliqués en tenant compte des propriétés physico-chimiques des charges et des interactions existant entre la résine polaire et le bois.

Notes: The present study investigates the pervaporation performance of four kinds of modified chitosan membranes to separate water from aqueous ethanol solution. Chitosan was prepared from chitin abstracted from the crab shell and subsequently deacetylated with aqueous NaOH solution. Modified chitosan membranes examined in this study include carboxymethyl chitosan, carboxyethyl chitosan, cyanoethyl chitosan, and amidoxime chitosan. The incorporation of hydrophilic functional groups into the 6-O position of chitosan enhances the selectivity of modified chitosan membrane compared to the previously reported chitosan-acetic acid complex membrane. Among the modified chitosan membranes, membranes containing carboxy groups show the best pervaporation performance. Carboxymethyl chitosan membranes show the maximum swelling and ethanol flux at approx. 15 wt.-% feed ethanol concentration due to the coupling and plasticizing effect.

Notes: Mechanische Parameter wie Elastizitätsmodul, Fliß- und Bruchspannung von aus der hochorientierten Schmelze hergestellten nadelkristallinen Mischungen aus Poly(propylen) und Poly(1-bute) wurden mit morphologischen Parametern, die aus Röntgenmessungen abgeleitet wurden, korreliert. Es wird gezeigt, daß der Elastizitätsmodul des Verbundes aus den E-Moduln der Fasern und der Matrix berechnet werden kann (Mischungsregel). Die an der Probe angreifenden Kräfte werden voll auf die Fasern übertragen; der Verbund kann daher als eigenfaserverstärktes System angesehen werden. Die Abschätzung der kritischen Faserlänge ergibt, daß die Festigkeit der FAsern voll ausgenutzt wird; der Bruch des Systems bei Belastung ist daher auf das Versagen der Fasern zurückzuführen. Das mechanische Verhalten des Verbundes wird stark beeinflußt durch die Komponentenzusammensetzung. Die longitudinale Struktur der Nadeln beider Komponenten bleibt unbeeinflußt von der jeweiligen Co-Komponente.

Notes: Water soluble cationic polyelectrolytes containing quaternary nitrogen atoms within the main chain were prepared via condensation polymerization of epichlorohydrin (ECH) with dimethylamine (DMA) and N,N-dialkylaminoalkylamines. The main parameters of the reaction that influence the polymer properties are: DMA/asymmetrical diamine molar ratio, the initial concentration of amine solution, NaOH/amine molar ratio, ECH/amine molar ratio, and asymmetrical diamine structure. The feature of flexible polyelectrolyte own to the investigated polymers was emphasized by the viscosimetric behaviour in dilute aqueous solutions with and without salt presence.

Notes: Antioxidants were attached to hydroxy-terminated liquid natural rubber by modified Friedel-Crafts alkylation reaction using anhydrous zinc chloride as catalyst. The rubber bound antioxidants were found to be less volatile and less extractable compared to conventional antioxidants. The bound antioxidants were tried both in latex compounds and dry rubber compounds. The vulcanizates showed improved ageing resistance compared to vulcanizates based on conventional antioxidants.

Notes: Current-voltage characteristics of polycarbonate samples (PC) have been studied in the voltage range 50-1000 V. The effect of UV-irradiation at λ = 225 and 300 nm, and thermal annealing on the electrical conductivity (σ) of PC was studied. The σ vs. 1/T relationship shows two slopes, i.e. two possible conduction mechanisms. The obtained results made it possible to determine a complete set of conduction parameters including activation energy and jump distance.

Notes: Terpolymers of acrylonitrile (AN), vinyl acetate (VA) (7.5-30 mol-%, related to AN), and divinylbenzene (DVB) (10 wt.-%) were prepared by suspension polymerization. The diluents used were mixtures of toluene or cyclohexanol (90 vol.-%) with solvents (10 vol.-%) such as hexadecane (HD), octane (O), dodecane (D), 2-ethylhexanol (E) or benzyl alcohol (B).It has been found that AN-VA-DVB terpolymers have a higher porosity, about 0.61-0.68, than corresponding AN-DVB copolymers. The terpolymers obtained with mixtures of various diluents differ in their supermolecular structure although they had similar porosity characteristics.The thermal effects accompanying heating of the terpolymers above 200°C significantly exceed that of nitrile groups cyclization observed of the other AN polymers.