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  • 1
    Electronic Resource
    Electronic Resource
    Firing rhythmicity in the neocortex in vivo and in vitro under sustained iontophoretic excitation (1996)
    Springer
    Journal of comparative physiology 178 (1996), S. 63-74 
    Details
    ISSN: 1432-1351
    Keywords: Spike train ; Autocorrelation analysis ; Background and spontaneous firing ; Cat ; Guinea-pig
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Extracellular recordings were made from the cat intact neocortex and guinea-pig neocortical slices during microiontophoretic application of amino acid neurotransmitters. Spike train autocorrelation analysis showed a high stability of firing patterns in the intact neocortex. When excitation of a cell was increased in a step-wise manner with glutamate iontophoresis only an enhancement of the rate of firing was observed. The rhythmic component, which was mainly due to periodic multiple discharges, remained up to the highest firing frequencies. In contrast to the in vivo observation, glutamate, aspartate or K+ iontophoresis in cortical slices resulted in firing pattern alternations (always from bursts or irregular activity to regular spike firing) as well as an increase in firing rate. In slices the periodic component was typically due to single-spike regularity and its frequency rose with an increase of firing rate. The comparison of autocorrelogram alternations in vivo and in vitro suggests that the temporal organization of spike trains in the intact cortex is under tight external control and is defined mainly by neuronal interactions, whereas virtually all the neurons in vitro are very sensitive to the same iontophoretic influences and their individual outputs easily change according to the excitation (depolarization) level. The coincidence of the lowest frequencies of single-spike regularity in the in vitro preparation (5–7 Hz and 8–10 Hz) with theta- and alpha-rhythms in the electroencephalogram (EEG), and with single unit firing rhythmicity in the whole brain, may represent the basis of a unit-circuit resonance and provide a high stability of these EEG-rhythms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00189591
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  • 2
    Electronic Resource
    Electronic Resource
    Lipoprotein Metabolism in Dogs and Cats (1996)
    Springer
    Comparative clinical pathology 6 (1996), S. 17-23 
    Details
    ISSN: 1433-2981
    Keywords: Cat ; Dog ; Hyperlipidaemia ; Lipoproteins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract High-density lipoproteins (HDL) are the predominant lipoproteins in plasma of dogs and cats and are the major cholesterol-carrying particles. Two HDL subfractions are identifiable in dog: small, dense particles (equivalent to human HDL3) and large, buoyant particles called HDL1, which overlap in hydrated density with low-density lipoproteins (LDL). The HDL1 are enriched in cholesterol and apolipoprotein (apo) E, and are prevalent in dogs fed high amounts of cholesterol and, or, saturated fat, when they are also referred to as HDLc. Lipoproteins similar to human HDL2 and HDL3 are identifiable in feline plasma, along with trace HDL1. Lipoprotein lipase (LPL), hepatic lipase (HL) and lecithin: cholesterol acyl transferase (LCAT) activities are present in dogs and cats. Both species lack significant cholesteryl ester transfer protein activity, and reverse cholesterol transport is probably accomplished by receptor-mediated hepatic uptake of HDL1. Methods for the measurement of canine and feline plasma lipoprotein-cholesterol concentrations, apolipoprotein concentrations, and the activities of LPL, HL and LCAT have been developed. Together with oral and intravenous fat tolerance tests, these methods provide the basis for studying lipoprotein metabolism in cats and dogs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00368097
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  • 3
    Electronic Resource
    Electronic Resource
    Senile plaques in very aged cats (1996)
    Springer
    Acta neuropathologica 91 (1996), S. 437-439 
    Details
    ISSN: 1432-0533
    Keywords: Key words Amyloid β-protein ; Cat ; Senile plaque
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Senile plaques were found in the cerebral cortices of three very aged cats (more than 18 years old). The plaques consisted of a coarse assembly of silver staining-positive materials, and was morphologically different from the well-known classical, primitive, and diffuse plaques. Congophilic amyloid angiopathy was observed in a few cortical arterioles of the oldest cat (20 years old). The senile plaques and a few cortical blood vessels were immunopositive for amyloid β-protein (Aβ). Aβ-positive materials were also sparsely distributed in the cortical neuropil but did not form senile plaques there. These findings should help to clarify the development of senile plaques and the early stage of Aβ deposition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004010050448
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  • 4
    Electronic Resource
    Electronic Resource
    On the mechanism of the post-activation depression of the H-reflex in human subjects (1996)
    Springer
    Experimental brain research 108 (1996), S. 450-462 
    Details
    ISSN: 1432-1106
    Keywords: Spinal cord ; H-reflexes ; Ia afferents ; Reflex pathways ; Homosynaptic depression ; Human ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract It was demonstrated that the soleus H-reflex was depressed for more than 10 s following a preceding passive dorsiflexion of the ankle joint. This depression was caused by activation of large-diameter afferents with receptors located in the leg muscles, as an ischaemic block of large-diameter fibres just below the knee joint abolished the depression, whereas a similar block just proximal to the ankle joint was ineffective. The depression of the H-reflex was not caused by changes in motoneuronal excitability, as motor-evoked potentials by magnetic brain stimulation were not depressed by the same passive dorsiflexion. Therefore it was concluded that the long-lasting depression is due to mechanisms acting at presynaptic level. The transmission of the monosynaptic Ia excitation from the femoral nerve to soleus motoneurones was not depressed by the ankle dorsiflexion. The depression thus seems to be confined to those afferents that were activated by the conditioning dorsiflexion. In parallel experiments on decerebrate cats, more invasive methods have complemented the indirect techniques used in the experiments on human subjects. A similar long-lasting depression of triceps surae monosynaptic reflexes was evoked by a preceding conditioning stimulation of the triceps surae Ia afferents. This depression was accompanied by a reduction of the monosynaptic Ia excitatory postsynaptic potential recorded intracellularly in triceps surae motoneurones, but not by changes in the input resistance or membrane potential in the motoneurones. Stimulation of separate branches within the triceps surae nerve demonstrated that the depression is confined to those afferents that were activated by the conditioning stimulus. This long-lasting depression was not accompanied by a dorsal root potential. It is concluded that the long-lasting depression is probably caused by a presynaptic effect, but different from the “classical” GABAergic presynaptic inhibition which is widely distributed among afferent fibres and accompanied by dorsal root potentials. It is more probably related to the phenomenon of a reduced transmitter release from previously activated fibres, i.e. a homosynaptic post-activation depression. The consequences of this post-activation depression for the interpretation of results on spinal mechanisms during voluntary movements in man are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00227268
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  • 5
    Electronic Resource
    Electronic Resource
    Light and electron microscopic analysis of synaptic input from cortical area 17 to the lateral posterior nucleus in cats (1996)
    Springer
    Experimental brain research 109 (1996), S. 63-70 
    Details
    ISSN: 1432-1106
    Keywords: Corticothalamic ; Thalamus ; Immunocytochemistry ; γ-aminobutyric acid ; Phaseolus vulgaris leucoagglutinin ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The morphology and synaptic organization of the corticothalamic (CT) fibres from area 17 were studied in the lateral posterior nucleus (LP) of the thalamus in cats. Injection of the anterograde tracer Phaseolus vulgaris leucoagglutinin (PHAL) into primary visual cortex labelled a band of CT fibres in the LP with terminal field confined to its lateral division “LP1”. PHAL-labelled CT axons in the LP1 gave rise to both en passant and terminal boutons. They usually established several synaptic contacts -often in complex glomerulus-like synaptic arrangements-with dendritic shafts of large diameter and presynaptic dendrites containing pleomorphic vesicles. Postsynaptic targets of the PHAL-labelled CT boutons were characterized by postembedding γ-aminobutyric acid (GABA) immunocytochemistry. It appeared that, in the LP1 of the cat, almost half (44.5%) of the postsynaptic dendrites to CT boutons from area 17 belonged to the GABA-immunopositive interneurons and the majority (41%) of these GABA-immunopositive dendrites were F2 terminals. These results indicate that the CT axons from the striate cortex in the LP of the cat, in addition to a direct excitatory action, exert a powerful feed-forward inhibition on the thalamic principal cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00228627
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  • 6
    Electronic Resource
    Electronic Resource
    Increased oxidative metabolism in middle suprasylvian cortex following removal of areas 17 and 18 from newborn cats (1996)
    Springer
    Experimental brain research 110 (1996), S. 335-346 
    Details
    ISSN: 1432-1106
    Keywords: Brain damage ; Cortical development ; Cytochrome oxidase ; Extrastriate cortex ; Neural plasticity ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We measured changes in metabolic activity in middle suprasylvian (MS) cortex of cats subjected to early or late removal of areas 17 and 18 to localize shifts in activity possibly indicative of regions within MS cortex that may receive expanded inputs and be involved in the sparing of some visual behaviors following early primary visual cortex damage. Cytochrome oxidase (CO) activity was measured in MS cortex of mature, intact cats and of others with areas 17 and 18 removed in adulthood (P180), or on postnatal day 28 (P28) or postnatal day 1 (P1). Not less than 9 months after the ablation, brain sections were prepared and reacted for the presence of CO. The density of CO reactivity in each of the six cortical layers in MS cortex was measured and standardized against densities from ventral periaqueductal gray or hypothalamus on the same section. Following lesions on P1, significant increases in CO activity occurred in deep layer III and in layer IV of the medial bank of the MS sulcus, including all of area PMLS and the posterior portion of AMLS. In contrast, there were no significant differences in the level of CO activity among P28, P180, or intact cats for any of the cortical layers, and all had lower levels than the P1 cats. This metabolic change provides an anatomical marker for localizing adjustments in MS cortex and can be linked to amplified projections into MS cortex from the thalamus (LPm and A and C laminae of the dorsal lateral geniculate nucleus) and ventral posterior suprasylvian cortex following P1 ablations. Furthermore, this neurochemical analysis implicates a distinct region of MS cortex as the cortical locus of some spared visual functions following early primary visual cortex damage.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00229134
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  • 7
    Electronic Resource
    Electronic Resource
    Response properties of relay cells in the A-laminae of the cat's dorsal lateral geniculate nucleus after saccades (1996)
    Springer
    Experimental brain research 110 (1996), S. 435-445 
    Details
    ISSN: 1432-1106
    Keywords: Vision ; Lateral geniculate nucleus ; Saccadic eye movements ; Suppression ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Responses of relay cells in the A-laminae of the dorsal lateral geniculate nucleus (LGNd) during spontaneous saccades and saccade-like visual stimulation were extracellularly recorded in awake cats. Ninety-six out of 137 cells recorded (42 X and 54 Y cells) were responsive during spontaneous saccadic eye movements. All Y cells and 67% of the X cells responded with burst activity, i.e. with either one or two activity peaks during and after saccades. Thirty-three percent of the X cells were inhibited during saccades. Excitatory peaks occurred at mean latencies of 33 ms and 31 ms for X and Y cells, respectively. Comparable burst responses were obtained when retinal image shifts similar to those during saccades were induced by external saccade-like stimulus movements. However, the latencies of excitatory peak activity were significantly longer to external stimuli than to the onsets of saccades. This indicates the existence of an eye movement-related input which activates LGNd relay cells in addition to the visual input. We propose that the pretectogeniculate projection may contribute to the responses of LGNd relay cells following saccadic eye movements via a disinhibitory input and that this input could be involved in intra- and postsaccadic modulations of the transfer of visual signals to visual cortex.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00229143
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  • 8
    Electronic Resource
    Electronic Resource
    Spatial coordination by descending vestibular signals (1996)
    Springer
    Experimental brain research 108 (1996), S. 85-100 
    Details
    ISSN: 1432-1106
    Keywords: Vestibulospinal reflexes ; Medial vestibulospinal tract neurons ; Lateral vestibulospinal tract neurons ; Semicircular canal convergence ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Spatial response properties of medial (MVST) and lateral (LVST) vestibulospinal tract neurons were studied in alert and decerebrate cats during sinusoidal angular rotations of the whole body in the horizontal and many vertical planes. Of 220 vestibulospinal neurons with activity modulated during 0.5-Hz sinusoidal rotations, 200 neurons exhibited response gains that varied as a cosine function of stimulus orientation and phases that were near head velocity for rotation planes far from the minimum response plane. A maximum activation direction vector (MAD), which represents the axis and direction of rotation that maximally excites the neuron, was calculated for these neurons. Spatial properties of secondary MVST neurons in alert and decerebrate animals were similar. The responses of 88 of 134 neurons (66%) could be accounted for by input from one semicircular canal pair. Of these, 84 had responses consistent with excitation from the ipsilateral canal of the pair (13 horizontal, 27 anterior, 44 posterior) and 4 with excitation from the contralateral horizontal canal. The responses of the remaining 46 (34%) neurons suggested convergent inputs. The activity of 38 of these was significantly modulated by both horizontal and vertical rotations. Twelve neurons (9%) had responses that were consistent with input from both vertical canal pairs, including 9 cells with MADs near the roll axis. Thirty-two secondary MVST neurons (24%) had type II yaw and/or roll responses. The spatial response properties of 18 secondary LVST neurons, all studied in decerebrate animals, were different from those of secondary MVST neurons. Sixteen neurons (89%) had type II yaw and/or roll responses, and 12 (67%) appeared to receive convergent canal pair input. Convergent input was more common on higher-order vestibulospinal neurons than on secondary neurons. These results suggest that MVST and LVST neurons and previously reported vestibulo-ocular neurons transmit functionally different signals. LVST neurons, particularly those with MADs close to the roll axis, may be involved in the vestibular-limb reflex. The combination of vertical and ipsilateral horizontal canal input on many secondary MVST neurons suggests a contribution to the vestibulocollic reflex. However, in contrast to most neck muscles, very few neurons had maximum vertical responses near pitch.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00242906
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  • 9
    Electronic Resource
    Electronic Resource
    Responses of medullary reticulospinal neurones to stimulation of cutaneous limb nerves during locomotion in intact cats (1996)
    Springer
    Experimental brain research 111 (1996), S. 153-168 
    Details
    ISSN: 1432-1106
    Keywords: Locomotion ; Reticulospinal neurones ; Cutaneous afferents ; Gating ; Postural control ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The present study was designed to determine whether the transmission of cutaneous afferent information from the limbs to the medullary reticular formation is phasically modulated during locomotion. Experiments were carried out in three chronically prepared, intact cats in which nerve cuff electrodes were placed, bilaterally, on the superficial radial and the superficial peroneal nerves. Thirty-seven reticulospinal neurones (RSNs) were identified by stimulation of their axons in the lumbar spinal cord (L2); 29 of 37 of these were recorded with the cat at rest, 28 of 37 during locomotion and 20 of 37 both at rest and during locomotion. Low-threshold stimulation of the cutaneous nerves evoked excitatory responses in the majority of RSNs both at rest and during locomotion. In the 28 of 37 RSNs recorded during locomotion, it was possible to record the evoked response to stimulation of all four limb nerves, giving a total of 184 tested cases [RSNs testedxnumber of nerves stimulatedxphase of stimulation (swing or stance)]. The responses of most RSNs to cutaneous stimulation were modulated in a phase-dependent manner during locomotion. The maximal responses in most, but not all, cases were obtained during the swing phase of the limb that was stimulated and were largely independent of the discharge pattern of the cell. We interpret this result as indicating that the efficacy of transmission of the afferent information is determined more by the excitability of the spinal relay neurones than by the level of excitability of the RSNs in the brainstem. It is suggested that the base discharge pattern of RSNs might be largely determined by their central afferent input, while peripheral afferent inputs would primarily serve to modify the RSN discharge pattern in response to perturbations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00227294
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  • 10
    Electronic Resource
    Electronic Resource
    Segmental and supraspinal control of synaptic effectiveness of functionally identified muscle afferents in the cat (1996)
    Springer
    Experimental brain research 107 (1996), S. 391-404 
    Details
    ISSN: 1432-1106
    Keywords: Primary afferent depolarization ; Presynaptic inhibition ; Muscle afferents ; Spinal cord ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The present investigation documents the patterns of primary afferent depolarization (PAD) of single, functionally identified muscle afferents from the medial gastrocnemius nerve in the intact, anesthetized cat. Classification of the impaled muscle afferents as from muscle spindles or from tendon organs was made according to several criteria, which comprised measurement of conduction velocity and electrical threshold of the peripheral axons, and the maximal frequency followed by the afferent fibers during vibration, as well as the changes in discharge frequency during longitudinal stretch, the projection of the afferent fiber to the motor pool, and, in unparalyzed preparations, the changes in afferent activity during a muscle twitch. In confirmation of a previous study, we found that most muscle spindle afferents (46.1–66.6%, depending on the combination of criteria utilized for receptor classification) had a type A PAD pattern. That is, they were depolarized by stimulation of group I fibers of the posterior biceps and semitendinosus (PBSt) nerve, but not by stimulation of cutaneous nerves (sural and superficial peroneus) or the bulbar reticular formation (RF), which in many cases inhibited the PBSt-induced PAD. In addition, we found a significant fraction of muscle spindle primaries that were depolarized by stimulation of group I PBSt fibers and also by stimulation of the bulbar RF. Stimulation of cutaneous nerves produced PAD in 9.1–31.2% of these fibers (type B PAD pattern) and no PAD in 8.2–15.4% (type C PAD pattern). In contrast to muscle spindle afferents, only the 7.7–15.4% of fibers from tendon organs had a type A PAD pattern, 23–46.1% had a type B and 50–61.5% a type C PAD pattern. These observations suggest that the neuronal circuitry involved in the control of the synaptic effectiveness of muscle spindles and tendon organs is subjected to excitatory as well as to inhibitory influences from cutaneous and reticulospinal fibers. As shown in the accompanying paper, the balance between excitation and inhibition is not fixed, but can be changed by crushing the afferent axons in the peripheral nerve and allowing subsequent reconnection of these afferent fibers with muscle receptors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00230421
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  • 11
    Electronic Resource
    Electronic Resource
    Differential spinal projections from the forelimb areas of the rostral and caudal subregions of primary motor cortex in the cat (1996)
    Springer
    Experimental brain research 108 (1996), S. 191-205 
    Details
    ISSN: 1432-1106
    Keywords: Spinal cord ; Dorsal horn ; Ventral horn ; Intermediate zone ; Propriospinal neurons ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We used anterograde transport of WGA-HRP to examine the topography of corticospinal projections from the forelimb areas within the rostral and caudal motor cortex subregions in the cat. We compared the pattern of these projections with those from the somatic sensory cortex. The principal finding of this study was that the laminar distribution of projections to the contralateral gray matter from the two motor cortex subregions was different. The rostral motor cortex projected preferentially to laminae VI–VIII, whereas caudal motor cortex projected primarily to laminae IV–VI. Confirming earlier findings, somatic sensory cortex projected predominantly to laminae I–VI inclusive. We found that only rostral motor cortex projected to territories in the rostral cervical cord containing propriospinal neurons of cervical spinal segments C3-4 and, in the cervical enlargement, to portions presumed to contain Ia inhibitory interneurons. We generated contour maps of labeling probability on averaged segmental distributions of anterograde labeling for all analyzed sections using the same algorithm. For rostral motor cortex, heaviest label in the dorsal part of lamina VII in the contralateral cord was consistently located in separate medial and lateral zones. In contrast, no consistent differences in the mediolateral location of label was noted for caudal motor cortex. To summarize, laminae I–III received input only from the somatic sensory cortex, while laminae IV–V received input from both somatic sensory and caudal motor cortex. Lamina VI received input from all cortical fields examined. Laminae VII–IX received input selectively from the rostral motor cortex. For motor cortex, our findings suggest that projections from the two subregions comprise separate descending pathways that could play distinct functional roles in movement control and sensorimotor integration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00228094
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  • 12
    Electronic Resource
    Electronic Resource
    Activity of neurons of the subthalamic nucleus in relation to motor performance in the cat (1996)
    Springer
    Experimental brain research 108 (1996), S. 206-220 
    Details
    ISSN: 1432-1106
    Keywords: Subthalamic nucleus ; Pallidum ; Motor initiation ; Single-unit activity ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The activity of subthalamic nucleus neurons related to motor performance was studied in three unrestrained cats operantly conditioned to perform a lever-release movement. The movement was initiated either rapidly after the trigger stimulus (a brief sound) in a simple reaction-time paradigm or after a delay in trials identified by a tone cue. These paradigms were randomly presented. The activity of 171 neurons was recorded in the contralateral and in the ipsilateral subthalamic nucleus, with respect to the performing limb. The mean spontaneous activity of cells in the ipsilateral side (18.5±13.8 imp/s, mean±SD) was higher than that in the contralateral side (8.5±8.1 imp/s). A total of 145 cells (85%) presented significant changes in activity in relation to the lever-release movement (task-related cells). The remaining 26 cells were either related to other events of the task (n=15; lever-press or reinforcement occurrence) or not related at all to the task performance (n=11). The majority of changes of activity of task-related cells were initial increases in discharge, which started on average, 127 ms before movement onset and lasted several hundreds of milliseconds. These increases in discharge were more frequent in the contralateral side (75 of 80 task-related cells, 94%) than in the ipsilateral side (43 of 65 task-related cells, 66%). The changes in activity, either increases or decreases, occurred early after the trigger stimulus, since 62% of them had a latency of less than 100 ms. Although the mean latency of initial increases was rather similar in both sides (97 ms contralateral versus 104 ms ipsilateral), the contralateral side was characterized by a high proportion of very early responses (less than 20 ms). For most neurons, the early changes in activity described above were absent after the trigger stimulus in the delayed condition. For certain neurons, the changes in activity prior to movement were different in reactiontime condition and in delayed condition, showing that the pattern of activity preceding movement might depend on the temporal requirements for motor initiation. The results suggest that a significant proportion of subthalamic cells are involved in the preparation and the initiation phases of the lever-release movement studied, although other hypotheses (e.g. stimulus-related responses) cannot be definitely ruled out. The timings and patterns of the changes in activity observed in the subthalamic nucleus in the present study, and in the pallidal complex previously, cannot be explained easily by the classical scheme where the external pallidum inhibits the subthalamic nucleus. The results suggest rather that the subthalamic nucleus, driven by a yet-to-be-determined excitatory input, exerts an excitatory influence on the pallidum and plays a crucial role in the control of the basal ganglia output neurons.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00228095
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  • 13
    Electronic Resource
    Electronic Resource
    Binocular interactions and disparity coding in area 21a of cat extrastriate visual cortex (1996)
    Springer
    Experimental brain research 108 (1996), S. 257-272 
    Details
    ISSN: 1432-1106
    Keywords: Binocular positional disparities ; Orientation selectivity ; Binocular summation and facilitation ; Depth discrimination ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We have examined, using both qualitative and quantitative techniques, binocular interactions of extracellularly recorded single neurons in the extrastriate cortical area 21a of anaesthetized and paralysed cats. Consistent with previous reports we have found that: (a) all area 21a neurons were orientation-selective, with about 65% of them preferring orientations within 30° of the vertical; and (b) over 75% of area 21a cells could be activated through either eye. Furthermore, a significant minority (4 cells; about 10%) of a subpopulation of 39 neurons in which binocular interactions were examined quantitatively, were “obligatory binocular neurons”, that is, they responded very weakly, if at all, to the monocular stimuli presented through either eye but responded vigorously to simultaneous stimulation through both eyes. Almost 70% (27/39) of neurons tested quantitatively for binocular interaction have shown significant modulation (over 50%) of their peak responses in relation to binocular positional retinal disparities. The majority of neurons sensitive to binocular positional disparities resembled either “tuned excitatory” (22 cells; 56.5% of the sample) or “tuned inhibitory” (2 cells; 5% of our sample) cells. In particular, they gave, respectively, maximal or minimal responses to optimally oriented, moving photic stimuli when the receptive fields plotted through each eye completely or partially overlapped. Although neurons recorded in area 21a have relatively large receptive fields (mean width 3.3±1.1°; range 2.0–5.6°), the mean width of the disparity tuning curve (2.8±1.0°; range 1.3–4.8°) for our sample of area 21a neurons was similar to those of neurons with significantly smaller receptive fields, recorded in areas 17 and 18 of cat's primary visual cortex. We conclude that area 21a of the cat, like areas 17 and 18 of primary visual cortex, is likely to play an important role in binocular depth discrimination and might constitute a “higher order” area for stereoscopic binocular vision.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00228099
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  • 14
    Electronic Resource
    Electronic Resource
    Simulation of dynamic fusimotor effects in the discharge frequency of la afferents by prestretching the muscle spindle (1996)
    Springer
    Experimental brain research 108 (1996), S. 297-304 
    Details
    ISSN: 1432-1106
    Keywords: Dynamic γ stimulation ; Bag,1 Ia afferents ; Discharge pattern regularity ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The discharge patterns of primary muscle spindle afferents from the tibial anterior muscle of the cat were recorded under a ramp-and-hold stretch of constant amplitude (7 mm) and stretch rates varying between 1 and 50 mm/s. With seven Ia fibers, the discharge patterns were recorded under various dynamic γ stimulation frequencies of between 10 and 120 stimuli per second. With 26 passive spindle fibers of the type known as bag1 Ia fibers, the discharge patterns were obtained under progressively increasing prestretch of the muscle. From each discharge pattern the following discharge frequencies were read: the initial activity (the discharge frequency before the start of ramp stretching), the peak dynamic discharge (the discharge frequency at the end of the dynamic phase of stretching), the maximum static value (MSt; the discharge frequency at the beginning of the static phase of stretching), and the final static value (the discharge frequency at the end of the 3rd s of the plateau phase). These four discharge frequency values were plotted against MSt, in separate diagrams for the Ia fibers under dynamic γ stimulation and for the bag1 Ia fibers. The relationship between the four discharge frequency values and the MSt turned out to be the same or much the same for both groups of Ia fibers. This means that the two groups of Ia fibers produced (more or less) identical discharge patterns in response to the ramp-and-hold stretch. In addition, where Ia fibers of the two groups had the same MSt, their dynamic and static responses were determined. Under these circumstances no difference was found in respect to their stretch properties between Ia fibers of dynamically γ-activated spindles and bag1 Ia fibers of passive spindles. In the Discussion, the high degree of similarity in the behavior of the two groups of Ia fibers is explained in terms of the mechanical properties of intrafusal bag1 fibers, which render it likely that in passive intrafusal bag1 fibers stretch activation will evoke the same mechanical behavior as dynamic γ activation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00228102
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  • 15
    Electronic Resource
    Electronic Resource
    Effect of tris-(hydroxymethyl)-aminomethane on experimental focal cerebral ischemia (1996)
    Springer
    Experimental brain research 111 (1996), S. 51-56 
    Details
    ISSN: 1432-1106
    Keywords: Focal cerebral ischemia ; Cerebral acidosis ; Tris(hydroxymethyl)-aminomethane ; Brain edema ; Lactate ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Systemic and focal cerebral acidosis is considered deleterious to cell metabolism and neuronal recovery. We investigated the immediate effect of tris-(hyroxymethyl)-aminomethane (THAM), an alkalizing agent, on focal cerebral ischemia produced by occlusion of the left middle cerebral artery (MCA) in cats with systemic acidosis. Occlusion of MCA resulted in prompt decreases in local cerebral blood flow of the ipsilateral marginal and ectosylvian gyri from 47.7 ml/100 g per minute in control to 32.3 ml/100 g per minute and 8.3 ml/100 g per minute, respectively. In the control group, physiological saline was infused continuously and the treated group received 0.3 M THAM to normalize systemic and focal cerebral acidosis. There were no significant changes in the systemic arterial pressure, arterial PO2 and PCO2 throughout the experiments in the two groups. Arterial pH decreased from 7.42 to 7.30 in the control, while it remained normal during THAM treatment. Extracellular pH of the marginal gyrus (peri-infarct zone) decreased from 7.39 to 6.87 with 6 h ischemia in the control group. In THAM infusion, extracellular pH was kept between 7.26 and 7.29, which was significantly higher than the control group. THAM significantly decreased infarct volume and lactate and water contents of the gray matter in the marginal gyrus at 6 h after occlusion. It is concluded that THAM infusion immediately after ischemia onset is considered effective in improving acidosis at the site of ischemic penumbra and consequently reduces lactate production, brain edema, and infarct volume.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00229555
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  • 16
    Electronic Resource
    Electronic Resource
    Dorsal border periaqueductal gray neurons project to the area directly adjacent to the central canal ependyma of the C4-T8 spinal cord in the cat (1996)
    Springer
    Experimental brain research 112 (1996), S. 11-23 
    Details
    ISSN: 1432-1106
    Keywords: Periaqueductal gray ; Spinal cord ; Central canal ; Hypothalamohypophysial ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In a previous study horseradish peroxidase (HRP) injections in the upper thoracic and cervical spinal cord revealed some faintly labeled small neurons at the dorsal border of the periaqueductal gray (PAG). The present light microscopic and electronmicroscopic tracing study describes the precise location of these dorsal border PAG-spinal neurons and their terminal organization. Wheat germ agglutinin-conjugated HRP (WGA-HRP) injections into cervical and upper thoracic spinal segments resulted in several hundreds of small retrogradely labeled neurons at the dorsal border of the ipsilateral caudal PAG. These neurons were not found after injections in more caudal segments. WGA-HRP injections in the dorsal border PAG region surprisingly resulted in anterogradely labeled fibers terminating in the area dorsally and laterally adjoining the central canal ependyma of the C4-T8 spinal cord. No anterogradely labeled fibers were found more caudal in the spinal cord. The labeled fibers found in the upper cervical cord were not located in the area immediately adjoining the ependymal layer of the central canal, but in the lateral part of laminae VI, VII and VIII and in area X bilaterally. Electronmicroscopic results of one case show that the dorsal border PAG-spinal neurons terminate in the neuropil of the subependymal area and in the vicinity of the basal membranes of capillaries located laterally to the central canal. The terminal profiles contain electron-lucent and densecored vesicles, suggesting a heterogeneity of possible transmitters. A striking observation was the lack of synaptic contacts, suggesting nonsynaptic release from the profiles. The function of the dorsal border PAG-spinal projection is unknown, but considering the termination pattern of the dorsal border PAG neurons on the capillaries the intriguing similarity between this projection system and the hypothalamohypophysial system is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00227173
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  • 17
    Electronic Resource
    Electronic Resource
    Smooth eye movements evoked by electrical stimulation of the cat's superior colliculus (1996)
    Springer
    Experimental brain research 107 (1996), S. 382-390 
    Details
    ISSN: 1432-1106
    Keywords: Saccades ; Smooth eye movements ; Eye drifts ; Superior colliculus ; Cat ; Electrical stimulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Head-fixed gaze shifts were evoked by electrical stimulation of the deeper layers of the cat superior colliculus (SC). After a short latency, saccades were triggered with kinematics similar to those of visually guided saccades. When electrical stimulation was maintained for more than 150–200 ms, postsaccadic smooth eye movements (SEMs) were observed. These movements were characterized by a period of approximately constant velocity following the evoked saccade. Depending on electrode position, a single saccade followed by a slow displacement or a “staircase” of saccades interspersed by SEMs were evoked. Mean velocity decreased with increasing deviation of the eye in the orbit in the direction of the movement. In the situation where a single evoked saccade was followed by a smooth movement, the duration of the latter depended on the duration of the stimulation train. In the situation where evoked saccades converged towards a restricted region of the visual field (“goal”-directed or craniocentric saccades), the SEMs were directed towards the centre of this region and their mean velocity decreased as the eye approached the goal. The direction of induced SEMs depended on the site of stimulation, as is the case for saccadic eye movements, and was not modified by stimulation parameters (“place” code). On the other hand, mean velocity of the movements depended on the site of stimulation and on the frequency and intensity of the current (“rate” code), as reported for saccades in the cat. The kinematics of these postsaccadic SEMs are similar to the kinematics of slow, postsaccadic correction observed during visually triggered gaze shifts of the alert cat. These results support the hypothesis that the SC is not exclusively implicated in the control of fast refixation of gaze but also in controlling postsaccadic conjugate slow eye movements in the cat.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00230420
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  • 18
    Electronic Resource
    Electronic Resource
    Changes in PAD patterns of group I muscle afferents after a peripheral nerve crush (1996)
    Springer
    Experimental brain research 107 (1996), S. 405-421 
    Details
    ISSN: 1432-1106
    Keywords: Primary afferent depolarization ; Presynaptic inhibition ; Muscle afferents ; Nerve crush ; Spinal cord ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In the anesthetized cat we have analyzed the changes in primary afferent depolarization (PAD) evoked in single muscle spindle and tendon organ afferents at different times after their axons were crushed in the periphery and allowed to regenerate. Medial gastrocnemius (MG) afferents were depolarized by stimulation of group I fibers in the posterior biceps and semitendinosus nerve (PBSt), as soon as 2 weeks after crushing their axons in the periphery, in some cases before they could be activated by physiological stimulation of muscle receptors. Two to twelve weeks after crushing the MG nerve, stimulation of the PBSt produced PAD in all MG fibers reconnected with presumed muscle spindles and tendon organs. The mean amplitude of the PAD elicited in afferent fibers reconnected with muscle spindles was increased relative to values obtained from Ia fibers in intact (control) preparations, but remained essentially the same in fibers reconnected with tendon organs. Quite unexpectedly, we found that, between 2 and 12 weeks after crushing the MG nerve, stimulation of the bulbar reticular formation (RF) produced PAD in most afferent fibers reconnected with muscle spindle afferents. The mean amplitude of the PAD elicited in these fibers was significantly increased relative to the PAD elicited in muscle spindle afferents from intact preparations (from 0.08–0.4 to 0.47-0.34 mV). A substantial recovery was observed between 6 months and 2.5 years after the peripheral nerve injury. Stimulation of the sural (SU) nerve produced practically no PAD in muscle spindles from intact preparations, and this remained so in those afferents reconnected with muscle spindles impaled 2–12 weeks after the nerve crush. The mean amplitude of the PAD produced in afferent fibers reconnected with tendon organs by stimulation of the PBSt nerve and of the bulbar RF remained essentially the same as the PAD elicited in intact afferents. However, SU nerve stimulation produced a larger PAD in afferents reconnected with tendon organs 2–12 weeks after the nerve crush (mean PAD changed from 0.05-0.04 to 0.32-0.17 mV). The results obtained indicate that the PAD patterns of the afferent fibers reconnected with muscle spindle and tendon organ afferents are changed after crushing their axons in the periphery: stimulation of the bulbar RF appears to produce larger PAD in fibers reconnected with muscle spindles, and stimulation of cutaneous afferents produces larger PAD in fibers reconnected with tendon organs. It is suggested that these alterations in the patterns of PAD of muscle afferents result from central changes in the balance of excitatory and inhibitory influences acting on the segmental pathways mediating the PAD. Although the functional role of these changes has not been established, they may reflect compensatory changes aimed to adjust information arising from damaged afferents.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00230422
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  • 19
    Electronic Resource
    Electronic Resource
    Convergence of skin reflex and corticospinal effects in segmental and propriospinal pathways to forelimb motoneurones in the cat (1996)
    Springer
    Experimental brain research 107 (1996), S. 422-434 
    Details
    ISSN: 1432-1106
    Keywords: Forelimb motoneurones ; Cutaneous reflex ; Pyramidal tract ; Spinal cord ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The organization of facilitatory convergence from cutaneous afferents (Skin) and the corticospinal tract (pyramidal tract, Pyr) in pathways to forelimb motoneurones of mainly distal muscles was studied in anaesthetized cats by analysing postsynaptic potentials (PSPs), which were spatially facilitated by combinations of stimuli to the two sources at different time intervals. Conditioning Pyr volleys facilitated Skin-evoked PSPs of fixed (1.2–3.6 ms) central latencies (Skin PSPs), suggesting that disynaptic and polysynaptic skin reflex pathways are facilitated from the pyramidal tract. The shortest latencies (1.2–1.7 ms) of pyramidal facilitation suggested direct connection of pyramidal fibres with last order neurones of skin reflex pathways. Conditioning Skin volleys facilitated Pyr-evoked PSPs of fixed, mostly disynaptic latencies (1.0–2.5 ms; Pyr PSPs), suggesting that pyramido-motoneuronal pathways are facilitated from Skin at a premotoneuronal level. The shortest pathway from skin afferents to the premotor neurones appeared to be monosynaptic. Although Pyr and Skin volleys were mutually facilitating, the facilitation curve of Pyr PSPs and that of Skin PSPs were discontinuous to each other, with the peak facilitation at different Skin-Pyr volley intervals. Transection of the dorsal column (DC) at the C5/C6 border had little effect on the latencies or amplitudes evoked by maximal stimulation and the pyramidal facilitation of Skin PSPs. In contrast, the facilitation of Pyr PSPs by Skin stimulation was greatly decreased after the DC transection, and the facilitation curve of Pyr PSPs was continuous to that of Skin PSPs, with no separate peak. Latencies of Pyr PSPs ranged similarly to those in DC intact preparations. More rostral DC transection (C4/C5 border) reduced Skin-facilitated Pyr excitatory PSPs (EPSPs) less than C5/C6 lesions, suggesting that the C5 segment also contains neurones mediating Skin-facilitated Pyr EPSPs. The results show that convergence from skin afferents and the corticospinal tract occurs at premotor pathways of different cervical segments. We suggest that corticospinal facilitation of skin reflex occurs mostly in the brachial segments and Skin facilitation of cortico-motoneuronal effects takes place largely in the rostral cervical segments and partly in the brachial segments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00230423
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  • 20
    Electronic Resource
    Electronic Resource
    Activity of dorsal respiratory group inspiratory neurons during laryngeal-induced fictive coughing and swallowing in decerebrate cats (1996)
    Springer
    Experimental brain research 108 (1996), S. 247-256 
    Details
    ISSN: 1432-1106
    Keywords: Nucleus tractus solitarii ; Dorsal respiratory group ; Inspiratory neurons ; Superior laryngeal nerve ; Fictive coughing and swallowing ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Membrane potential changes and/or discharges from 36 inspiratory neurons were recorded intracellularly in the dorsal respiratory group (DRG; i.e., the ventrolateral subdivision of the nucleus tractus solitarii) in decerebrate, paralyzed, and ventilated cats. Electrical activities were recorded from both somata (n=10) and axons (n=26). Activities during quiet breathing were compared with those observed during fictive coughing and swallowing evoked by repetitive electrical stimulation of afferent fibers of the superior laryngeal nerve (SLN). These nonrespiratory behaviors were evident in paralyzed animals as characteristic discharge patterns of the phrenic, abdominal, and hypoglossal nerves. Twenty-six neurons exhibiting antidromic action potentials in response to electrical stimuli applied to the cervical (C3–5) spinal cord were classified as inspiratory bulbospinal neurons (IBSNs). These neurons were considered as premotoneurons. The remaining 10 inspiratory neurons (INAA) were not antidromically activated by electrical stimuli applied to either cervical spinal cord or ipsilateral cervical vagus. These neurons are thought to be propriobulbar neurons. We recorded the activity of 31 DRG inspiratory neurons (24 IBSNs and 7 I-NAA) during coughing. All but one (a late-recruited IBSN) discharged a burst of action potentials during the coughing-related phrenic nerve activity. Typically, ramp-like membrane depolarization trajectories and discharge frequencies during coughing were similar to those observed during inspiration. We recorded the activity of 33 DRG inspiratory neurons (23 IBSNs and 10 I-NAA) during swallowing. Most (28/33) neurons were briefly activated, i.e., discharged a burst of action potentials during swallowing, but peak discharge frequency decreased compared with that measured during inspiration. The membrane potentials of nine somata exhibited a brief bell-shaped depolarization during swallowing, the amplitude of which was similar to that observed during inspiration. These results suggest that some inspiratory premotoneurons and propriobulbar neurons of the DRG might be involved in nonrespiratory motor activities, even if clearly antagonistic to breathing (e.g., swallowing). We postulate the existence in the medulla oblongata of adult mammals of neurons exhibiting a “functional flexibility”.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00228098
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  • 21
    Electronic Resource
    Electronic Resource
    Firing properties of preposito-collicular neurones related to horizontal eye movements in the alert cat (1996)
    Springer
    Experimental brain research 110 (1996), S. 413-424 
    Details
    ISSN: 1432-1106
    Keywords: Prepositus hypoglossi nucleus ; Superior colliculus ; Eye position ; Eye velocity ; Feedback control ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The projection from the nucleus prepositus hypoglossi (PH) to the superior colliculus (SC) has been proposed to provide a feedback control of collicular saccadic activities. The present study aimed to identify the functional properties of PH neurones projecting to the SC relative to eye movement parameters. Preposito-collicular neurones were identified in alert cats by antidromic invasion and collision tests following electrical stimulations of the contralateral SC. Their discharges were then correlated with the horizontal component of eye movements. Particular attention was given to the timing of discharges relative to saccade onsets. Most prepositocollicular neurones (12/14) displayed transient activities associated to eye velocity, and onsets preceded the saccade onset by 9.4–19.9 ms. The mean eye velocity sensitivity of these “early” preposito-collicular neurones (1.46±0.53 spikes/s per degree per second) was quite similar to that calculated from a sample of putative motoneurones or interneurones that have been recorded within abducens nucleus and quantified in the same conditions. The remaining two preposito-collicular neurones exhibited transient activity related to saccades, but this followed the transient putative motoneuronal discharge. These “delayed” neurones also had lower eye velocity sensitivities (0.38 sp/s per degree per second and 0.58 sp/s per degree per second, respectively) compared with early neurones. Both classes of preposito-collicular neurones also displayed a subsequent tonic activity correlated with the eye position. Taken together, these results demonstrate that preposito-collicular neurones code both eye position and eye velocity just like ocular motoneurones, but in a predictive manner. The anticipatory discharge of early neurones makes them likely candidates for the control of peak activities of saccade-related collicular neurones, particularly in the caudal colliculus. Delayed preposito-collicular neurones may also participate in the control of collicular activities, but probably in more rostral SC, where peak activities occur later during eye movements together with smaller motor error coding.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00229141
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  • 22
    Electronic Resource
    Electronic Resource
    Peripheral nerve stimulation increases fos immunoreactivity without affecting type II Ca2+/calmodulin-dependent protein kinase, glutamic acid decarboxylase, or GABAA receptor gene expression in cat spinal cord (1996)
    Springer
    Experimental brain research 111 (1996), S. 326-336 
    Details
    ISSN: 1432-1106
    Keywords: Plasticity ; c-fos ; mRNAs ; Primary afferents ; In situ hybridization ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Expression patterns of the immediate early gene c-fos and of other genes including those for the α-subunit of type II Ca2+/calmodulin-dependent protein kinase (CaMKIIα), 67-kDa glutamic acid decarboxylase (GAD), and the α1-, β2-, and γ2-subunits of the GABAA receptor were described in the spinal cord of normal cats and following peripheral nerve stimulation. As revealed by in situ hybridization histochemistry, CaMKIIα messenger RNA (mRNA) is normally distributed only in cells of Rexed's laminae I–IV, whereas GAD mRNA is expressed by subpopulations of cells in all laminae, with the heaviest hybridization signal found in laminae I–III and medial parts of laminae V and VI. The three GABAA receptor subunits have varying expression patterns in the laminae. All of them are expressed by many cells located in the base of the dorsal horn and the intermediate zone, but only the γ2-subunit is intensely expressed by motoneurons. Single-pulse, electrical stimulation of the sciatic or median and ulnar nerves of anesthetized cats at a pulse rate of 1/s for 6–8 h failed to induce observable changes in gene expression for CaMKIIα, GAD, or for the three subunits of the GABAA receptor; although immunoreactivity for the protein products of c-fos (or c-fos-related genes) was markedly upregulated in some neurons of the dorsal horn and the intermediate zone. Therefore, under the present experimental conditions, upregulation of the immediate early gene c-fos (or c-fos-related genes) is not associated with changes in expression of late-effector genes potentially involved in central nervous system plasticity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00228722
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  • 23
    Electronic Resource
    Electronic Resource
    Properties of utricular nerve-activated vestibulospinal neurons in cats (1996)
    Springer
    Experimental brain research 112 (1996), S. 197-202 
    Details
    ISSN: 1432-1106
    Keywords: Utricular nerve ; Vestibulospinal neuron ; Lateral and medial vestibulospinal tracts ; Vestibular nuclei ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The axonal pathway, conduction velocities, and locations of the cell bodies of utricular nerve-activated vestibulospinal neurons were studied in decerebrated or anesthetized cats using the collision test of orthodromic and antidromic spikes. For orthodromic stimulation, bipolar tungsten electrodes were placed on the utricular nerve and the other vestibular nerve branches were transected. Monopolar tungsten electrodes were positioned on both sides of the upper cervical segments (C2–4), caudal end of the cervical enlargement (C7-T1), and from the lower thoracic to the upper lumbar segments (T12-L3) and were used for antidromic stimulation of the spinal cord. Another monopolar electrode was also placed in the oculomotor nucleus to study whether utricular nerve-activated vestibulospinal neurons have ascending branches to the oculomotor nucleus. Of the 173 vestibular neurons orthodromically activated by the stimulation of the utricular nerve, 46 were second-order vestibulospinal neurons and 5 were third-order neurons. The majority of the utricular nerve-activated vestibulospinal neurons were located in the rostral part of the descending vestibular nucleus and the caudal part of the ventral lateral nucleus. Seventy-three percent of the utricular nerve-activated vestibulospinal neurons descended through the ipsilateral lateral vestibulospinal tract. Approximately 80% of these neurons reached the cervicothoracic junction, but a few reached the upper lumbar spinal cord. Twenty-seven percent of the utricular nerve-activated vestibulospinal neurons descended through the medial vestibulospinal tract or the contralateral vestibulospinal tracts. Those axons terminated mainly in the upper cervical segments. Almost none of the utricular nerve-activated vestibular neurons had ascending branches to the oculomotor nucleus.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00227638
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  • 24
    Electronic Resource
    Electronic Resource
    Synaptic interactions of retrogradely labeled hypoglossal motoneurons with substance P-like immunoreactive nerve terminals in the cat: a dual-labeling electron microscopic study (1996)
    Springer
    Experimental brain research 110 (1996), S. 175-182 
    Details
    ISSN: 1432-1106
    Keywords: Hypoglossal motoneurons ; Retrograde transport ; Synaptic interactions ; Substance P ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract This study has investigated the synaptic interactions between hypoglossal motoneurons and substance P (SP)-immunoreactive terminals. Cholera toxin B conjugated to horseradish peroxidase was injected into the tip of the tongue on the right side of six ketamine-anesthetized cats. Two to five days later, the animals were killed. Cells containing HRP were labeled with a histochemical reaction utilizing tetramethylbenzidine (TMB) as the chromogen. TMB forms crystalline reaction products that are very distinct at the electron microscopic level. The tissues were then processed for immunocytochemisty using an antiserum against SP. The chromogen used in this case, di-aminobenzidine, yields amorphous reaction products. At the light microscopic level, labeled cells were observed primarily ipsilaterally in both intermediate and ventrolateral subdivisions of the hypoglossal nucleus. The majority of these labeled cells were seen at the level of obex. At the electron microscopic level, both asymmetric and symmetric synapses were observed. SP-immunoreactive nerve terminals formed asymmetric synapses with labeled dendrites and symmetric synapses with labeled perikarya. SP-labeled terminals also synapsed on unlabeled dendrites and somata. These are the first ultrastructural studies demonstrating synaptic interactions between hypoglossal motoneurons and SP terminals. These studies demonstrate that hypoglossal motoneurons that innervate intrinsic tongue muscles are modulated by SP and that SP may play a role in the control of fine movements of the tongue.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00228549
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  • 25
    Electronic Resource
    Electronic Resource
    Neural connectivity only accounts for a small part of neural correlation in auditory cortex (1996)
    Springer
    Experimental brain research 110 (1996), S. 379-391 
    Details
    ISSN: 1432-1106
    Keywords: Auditory cortex ; Cross-correlograms ; Cross-interval histograms ; Burst-firing ; Neural interaction ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In order to allow the relation of functional connectivity patterns (inferred from cross-correlograms) to structural connectivity (the anatomical substrate), we analyzed cross-correlogram peaks for spontaneous and stimulated activity in the auditory cortex. It was assumed that the broad correlograms, usually encountered, represent neural connectivity as well as secondary effects such as intrinsic firing patterns, global synchrony related to the ongoing electroencephalographic activity, and stimulus-related effects. Data were collected from 604 neuron pairs recorded under spontaneous conditions in primary auditory cortex of seven juvenile (30–70 days) and nine adult cats. Three hundred and six pairs (51%) had a peak cross-correlation coefficient significantly different from zero. For 113 neuron pairs out of this subgroup, correlations were calculated also for spike trains recorded during click stimulation. After a combined burst-correction and deconvolution procedure was carried out, the correlation peak strengths were not significantly changed for spontaneous activity, but peak width was narrower for single-electrode pairs than for dual-electrode pairs, suggesting a better synchronization for neighboring neurons. Under click stimulation conditions, overall peak synchronization strength was independent of interelectrode distance, whereas, after correction for secondary and stimulus effects, peak synchronization was significantly lower for dual-electrode pairs. However, the primary peak width for single-electrode pairs under stimulus conditions was no longer different from that of dual-electrode pairs. This implies that both under spontaneous and stimulus conditions secondary effects largely obscure any underlying correlation produced by anatomical connectivity. The secondary effects may be the result of intrinsic as well as network properties in auditory cortex and may functionally be more important than the weak primary effects resulting from anatomical connections. Cross-interval analysis suggests that the correlations in auditory cortex are dynamic and may show random switching between states of stronger and weaker synchronization.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00229138
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  • 26
    Electronic Resource
    Electronic Resource
    Intrinsic tone and distensibility of in vitro and in situ cat pulmonary arteries (1996)
    Springer
    Lung 174 (1996), S. 291-301 
    Details
    ISSN: 1432-1750
    Keywords: Pulmonary artery ; Vascular angiography ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract This study was designed to determine the in vitro and in situ diameter vs pressure relationship of 200- to 1,200-μm diameter pulmonary arteries in the cat. Diameter vs pressure relationships of these arteries were obtained using two methods, microscopic observation of in vitro cannulated and pressurized arteries and X-ray angiography of in situ arteries. Both in vitro and in situ arteries were studied first under normal conditions and then after reducing tone with Ca2+-free solution (in vitro) or papaverine (in situ). In vitro arteries commonly increased their tone in response to elevated transmural pressure, and in some cases, the diameter actually decreased as pressure increased. This behavior was not observed in the in situ arteries. The major difference between in vitro and in situ arteries was that when the in vitro arteries were relaxed, the slope of the diameter vs pressure curves increased, whereas the slope was not altered significantly by relaxation of the in situ arteries. This difference is emphasized by the increased distensibility with relaxation of the in vitro arteries but the decreased distensibility with relaxation of the in situ arteries. The results of this study suggest that, at least in the cat, small pulmonary arteries possess a mechanism that is dormant in the in situ environment within the normal lung. However, the potential for pressure-induced constriction may be unmasked by changing the vessel history and/or environment. Extrapolating results obtained from in vitro pulmonary arteries to the in situ situation should therefore be done with caution. Studies directed at what factors contribute to differences in the responses of in vitro and in situ arteries might help in understanding pulmonary vascular pathophysiology.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00176188
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