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  • 1
    Electronic Resource
    Electronic Resource
    Short-latency peripheral inputs to thalamic neurones projecting to the motor cortex in the monkey (1979)
    Springer
    Experimental brain research 36 (1979), S. 445-462 
    Details
    ISSN: 1432-1106
    Keywords: Monkey ; Thalamus ; Motor cortex
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary One hundred seventy-five neurones in the n.ventroposterior lateralis (VPL) and n.ventralis lateralis (VL) in the thalamus of anaesthetised monkeys have been tested antidromically for projection to the cortex and for somatosensory input from the contralateral arm. Using bipolar stimulation of the cortical surface, 113 thalamic neurones were successfully identified as antidromically driven from the hand area of the postcentral gyrus (48 neurones) or from the hand area of the precentral gyrus (65 neurones). All but one of these 113 neurones could only be antidromically discharged from the postcentral cortex or from the precentral cortex, and not from both. Most had antidromic latencies between 0.5 and 1.5 ms. Twenty-five/sixty-five precentrally projecting neurones and 45/48 postcentrally projecting neurones were activated by stimulation of the contralateral median or radial nerves. Both groups responded at short latency (4–8 ms) and many were activated by low-threshold shocks (0.8–1.3 T) and had restricted receptive fields on the hand. Precentrally projecting neurones responded most powerfully to joint movement or deep pressure, and some of these neurones were also responsive to cutaneous stimuli. Precentrally projecting neurones with peripheral inputs were all found in the oral subdivision of the VPL (the VPLo). The properties of these neurones suggest that they may be partly responsible for rapid somatosensory input to the motor cortex.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00238515
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  • 2
    Electronic Resource
    Electronic Resource
    Absence of callosal collaterals derived from rat corticospinal neurons (1980)
    Springer
    Experimental brain research 39 (1980), S. 433-440 
    Details
    ISSN: 1432-1106
    Keywords: Callosum ; Cortex ; Fluorescent retrograde tracing ; Electrophysiology ; Corticospinal branching
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In rat the presence of axon collaterals from corticospinal neurons to the contralateral hemisphere has been investigated by means of anatomical and electrophysiological techniques. Anatomical Experiments. Several combinations of fluorescent retrograde tracers were used. In eight rats injections of Evans Blue, “True Blue”, “Fast Blue” or DAPI-Primuline were made in areas 10, 6, and 4 and in the most medial part of the S1 granular cortex of one hemisphere, 1.5 mm below cortical surface. These injections were combined with injections of “Fast Blue”, DAPI-Primuline, “Granular Blue”, “Nuclear Yellow”, or Bisbenzimide in the ipsilateral corticospinal tract in the C2 segment. Survival times of the animals varied according to the tracers used. In the non-injected hemisphere the retrogradely labeled corticospinal neurons were present in layer V of especially areas 10, 6, 4 and the medial portion of the S1 granular cortex. However, the retrogradely labeled callosal neurons in these areas were present in all layers except layer I. The labeled callosal and corticospinal neurons in layer V were intermingled and frequently situated very close to one another. However, with none of the tracer combinations were double labeled neurons observed. Electrophysiological Experiments. In six rats, layer V neurons of hindlimb-sensorimotor cortex were tested for antidromic responses to stimulation of contralateral corticospinal tract (CST) and corpus callosum (CC). Eighty-five CST neurons were identified, none of which responded antidromically to CC shocks. Eighty-two layer V neurons were identified which responded antidromically to CC shocks, but none of them responded antidromically to CST shocks. CC shocks elicited strong synaptic responses in CST neurons and vice versa. Depth measures indicated extensive intermingling of CST and CC neurons. From both sets of findings it was concluded that, in rat, CST neurons do not give rise to callosal collaterals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00239308
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  • 3
    Electronic Resource
    Electronic Resource
    Cortical afferents and efferents of monkey postarcuate area: an anatomical and electrophysiological study (1984)
    Springer
    Experimental brain research 56 (1984), S. 410-424 
    Details
    ISSN: 1432-1106
    Keywords: Cortex ; Monkey ; Postarcuate area ; Premotor area
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A study has been made of the corticocortical efferent and afferent connections of the posterior bank of the arcuate sulcus in the macaque monkey. The distribution of efferent projections to the primary motor cortex (MI) was studied by injecting three different fluorescent retrograde tracers into separate regions of MI. The resultant labeling showed a discrete and topographically organized projection: neurons lying below the inferior limb of the arcuate sulcus project into the MI face area, while neurons located in the posterior bank of the inferior limb of the arcuate sulcus and in the arcuate spur region project into the MI hand area. These findings were confirmed electrophysiologically by demonstrating that postarcuate neurons could only be activated antidromically by stimulation within restricted regions of MI. HRP injections within postarcuate cortex indicated that afferents to this region arise from a number of cortical areas. However, the largest numbers of labeled neurons were found in the posterior parietal cortex (area 7b; PF) and in the secondary somatosensory region (SII). Neurons in both 7b (PF) and SII could be antidromically activated by postarcuate stimulation. It was further shown that stimulation of area 7b (PF) gives rise to short-latency synaptic responses in postarcuate neurons, including some neurons with identified projections to MI. The results are discussed in relation to the possible function of the postarcuate region of the premotor cortex in the sensory guidance of movement.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00237982
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  • 4
    Electronic Resource
    Electronic Resource
    Recording and identification of single motor units in the free-to-move primate hand (1990)
    Springer
    Experimental brain research 81 (1990), S. 95-106 
    Details
    ISSN: 1432-1106
    Keywords: Motor unit ; Hand muscles ; Monkey ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A new technique is described for recording the activity of single motor units in human or monkey hand muscles. A pair of microwire electrodes is introduced into the muscle using a fine needle. After insertion, the needle can be completely removed, leaving the recording microwires in situ. The method allows stable recording of a motor unit during natural movement of the hand and fingers. The identity of a given single motor unit was reflected in the form and amplitude of the motor unit-triggered average (MU-TA), derived by averaging the unrectified surface EMG recorded from the muscle with discharges of the motor unit. The MU-TA of a given unit remained constant despite variations in the form and size of its action potential. Inspection of successive MU-TAs increased confidence that records were taken from one and the same unit over long recording periods. Control experiments in human first dorsal interosseous showed that the peak-to-peak amplitude of the MU-TA was highly correlated with both the twitch force (r= 0.65–0.92, mean 0.82, six subjects) and force threshold (r=0.62–0.93, mean 0.83) of a given unit. Similar findings were obtained for human abductor pollicis brevis (AbPB) motor units. In the monkey, AbPB motor units which were recruited early in a precision grip task and which discharged steadily during the grip had smaller MU-TAs than laterecruited, phasic units. The combination of methods described in this paper enable a single motor unit to be identified and recognised. The relative size of the unit, which is an important parameter in most motor unit studies, can be reliably estimated from the amplitude of the MU-TA. This allows indirect assessment of motor unit size in a free-to-move animal.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00230105
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  • 5
    Electronic Resource
    Electronic Resource
    The development of corticospinal projections to tail and hindlimb motoneurons studied in infant macaques using magnetic brain stimulation (1992)
    Springer
    Experimental brain research 90 (1992), S. 225-228 
    Details
    ISSN: 1432-1106
    Keywords: Rhesus monkey ; Magnetic brain stimulation ; Development ; Cortico-motoneuronal cells
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The EMG responses evoked in tail, leg and foot muscles by magnetic stimulation (MS) of the brain were investigated in two male macaque monkeys under ketamine sedation. The animals were studied longitudinally over a period of 7 months (from 2.75 to 9.75 months old). MS was generally ineffective in eliciting responses when the animals were 2.75–4.5 months old, even at maximum stimulator output (1.5 Tesla). After this time the threshold for evoking EMG responses decreased considerably, and there was an increase in the probability of occurrence of the responses. These age-related changes plateaued at about 7.5 months, after which they remained fairly constant at adult levels. In both animals the maturation of these responses in tail and hindlimb muscles occurred later than in forelimb muscles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00229276
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  • 6
    Electronic Resource
    Electronic Resource
    The effects upon the activity of hand and forearm muscles of intracortical stimulation in the vicinity of corticomotor neurones in the conscious monkey (1987)
    Springer
    Experimental brain research 66 (1987), S. 621-637 
    Details
    ISSN: 1432-1106
    Keywords: Monkey ; Motor cortex ; Intracortical stimulation ; Corticospinal tract
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Corticomotor (CM) neurones were identified in three conscious macaque monkeys by the presence of post-spike facilitation (PSF) in spike-triggered averages of e.m.g. recorded from intrinsic hand and forearm muscles during performance of a precision grip task. Post-spike effects were compared with those produced by single-pulse intracortical microstimulation (ICMS), with strengths of 4–20 μA, delivered at the site of 47 CM cells. Most muscles facilitated by a CM cell were also facilitated by ICMS at the site of the cell. ICMS effects were stronger: at 10 μA, the amplitude of ICMS-evoked facilitation was on average 2.8 times greater than PSF, and 6.9 times greater at 20 μA. Onset latency of ICMS-evoked facilitation was consistently longer (by 1.7 and 1.3 ms at 10 and 20 μA respectively) than PSF, and it is suggested that this results from the indirect, trans-synaptic excitation of CM cells by ICMS. Post-spike suppression was rarely seen (7/421 compared to 105/421 cases of PSF). In contrast, suppression and facilitation were equally common in response to ICMS. The synaptic mechanisms underlying these effects were explored in 5 anaesthetised macaque monkeys. ICMS facilitated a greater proportion of the tested muscles than did the CM cell recorded at the stimulus site. The results suggest the juxtaposition in the motor cortex of CM neurones with different ‘muscle fields’. The merits of STA and ICMS for exploring cortical organisation are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00270695
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  • 7
    Electronic Resource
    Electronic Resource
    The effect of polyhydroxyphenols on brain ATP in the mouse (1969)
    Springer
    Experimental brain research 7 (1969), S. 250-257 
    Details
    ISSN: 1432-1106
    Keywords: Polyhydroxyphenols ; Mouse ; Brain ; ATP ; Convulsions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The penetration of pyrogallol and catechol into the brains of mice after an intraperitoneal injection has been studied together with their effects on locomotor activity and on the concentration of cerebral ATP. A 60 mg/kg dose of catechol produced convulsive activity together with a decrease in concentration of brain ATP. The time courses of these effects were similar, and closely followed the time course of catechol penetration into the brain, all showing peak changes at 3 min. 60 mg/kg pyrogallol did not produce convulsive activity although there was a fall in concentration of cerebral ATP of the same order (20–30%) as that produced by the same dose of catechol. There was also a marked similarity between the cerebral penetration of pyrogallol and the time course of the fall of ATP it produced, although penetration was slower and maximal changes were observed 10 min after injection. Both catechol and pyrogallol produced similar changes of ATP in the cerebral hemispheres, thalamus, medulla, and cerebellum of mice whose brains were divided prior to estimation. In a further attempt to determine if there was any correlation between brain levels of ATP and convulsive activity it was found that: 1. A lower dose of catechol (40 mg/kg), which still produced convulsions, had less effect on the cerebral ATP than did a non-convulsive dose of pyrogallol (60 mg/kg). 2. 60 mg/kg catechol produces typical convulsions in mice respiring a 95% O2, 5% CO2 gas mixture, but there was no significant change in brain levels of ATP in these mice. It is concluded that there is no correlation between the convulsive action of catechol and the fall in brain concentration of ATP produced by this compound.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00239032
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  • 8
    Electronic Resource
    Electronic Resource
    Recruitment order of motoneurons during functional tasks (1994)
    Springer
    Experimental brain research 79 (1994), S. 503-508 
    Details
    ISSN: 1432-1106
    Keywords: Recruitment ; Motoneuron ; Motor unit ; First dorsal interosseus ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The recruitment order of motoneurons of first dorsal interosseous (1DI) muscle has been shown to be the same during either isometric abduction or flexion of the index finger. However, it is not known whether this stereotyped recruitment is the same for all functional tasks. This question was addressed by using the 1DI muscle, which contributes to many functional tasks involving the hand and fingers. Single motor units and surface electromyographic activity were recorded from 1DI in three human subjects. Each subject performed tasks of abduction of the index finger, rotation to unscrew a threaded knob and pincer to close a springloaded clip. The same motor units were activated for each of the three tasks, providing no evidence for the existence of task groups. The order of recruitment of pairs of selected motor units was the same for each of the three tasks.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00229189
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  • 9
    Electronic Resource
    Electronic Resource
    An investigation of the intrinsic circuitry of the motor cortex of the monkey using intra-cortical microstimulation (1998)
    Springer
    Experimental brain research 123 (1998), S. 397-411 
    Details
    ISSN: 1432-1106
    Keywords: Key words Motor cortex ; Monkey ; Intracortical microstimulation ; EMG
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The motor cortex contains a distributed map of muscles, with a single muscle represented over a wide cortical area. We have searched for inter-connections between distant sites projecting to common muscles by delivering pairs of 20-µA single-pulse intracortical microstimuli (ICMS) to sites separated by 1.5–2 mm in the hand-area primary motor cortex of two macaque monkeys performing a precision grip task. The facilitation of hand- and forearm-muscle rectified EMG was measured. When stimuli were delivered simultaneously, responses were quantified using a technique to correct for non-linearities inherent in the use of averaged, rectified EMG. A spatial facilitation was seen for such simultaneous stimuli; however, it was of the same magnitude as that occurring when ICMS was paired with stimulation of corticospinal axons in the pyramidal tract (PT), so that it was likely to be spinal in origin. When two such distant sites were stimulated separated by a 10- or 20-ms delay, the second response scaled with the level of background EMG in the same way as a response to the PT stimulus. By contrast, when the same site was stimulated twice with these delays, the second response showed a facilitation compared with a similarly timed PT response. There would therefore appear to be a local facilitation of the cortical output at these intervals, which is not seen between distant sites. Antidromically identified pyramidal-tract neurones (PTNs) were recorded whilst stimuli were delivered to a cortical site, with a distance between stimulating and recording electrodes of also 1.5–2 mm. The most common response was a facilitation followed by a suppression. Six of eleven PTNs showed a facilitation in their discharge following this stimulation (maximum connection strength s=0.19), 8/11 showed a suppression (maximum s=0.16). It is concluded that powerful inter-connections do exist between distributed parts of the motor output and that there is widespread cortical activation after even a single ICMS pulse. However, these inter-connections do not lead to interactions between cortical outputs following stimulation, as assessed from the EMG. It is proposed that this is likely to reflect differences in the summation of output cells to local versus remote stimulation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002210050585
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  • 10
    Electronic Resource
    Electronic Resource
    Neural control of dexterity: what has been achieved? (1999)
    Springer
    Experimental brain research 128 (1999), S. 6-12 
    Details
    ISSN: 1432-1106
    Keywords: Key words Hand ; Primate ; Monkey ; Cortex
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  This chapter reviews progress made in our understanding of the neural control of dexterity. It stresses the increasing benefit derived by uniting the different disciplines concerned with the study of the hand. It highlights the study of natural movements and of the importance of tackling the function of the interface between the neural control system and the biomechanical appartus of the hand and arm. It also highlights the distributed nature of the control system, its utilisation of complex spatio-temporal representations and its dependence on sensory input. It concludes by pointing out the lessons that have been learned from two fields of work: the development of motor skill and the comparative study of dexterity in different primate species
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002210050811
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