Unit responses of the thalamic and ventral anterior thalamic nuclei to electrical stimulation of thalamic relay nuclei in cats

Responses of 92 neurons of the reticular (R) and 105 neurons of the ventral anterior (VA) thalamic nuclei to stimulation of the ventrobasal complex (VB) and the lateral (GL) and medial (GM) geniculate bodies were investigated in cats immobilized with D-tobocurarine. Altogether 72.2% of R neurons and 76.2% of VA neurons responded to stimulation of VB whereas only 15.0% of R neurons and 27.1% of VA neurons responded to stimulation of GM and 10.2% of R neurons and 19.6% of VA neurons responded to stimulation of GL. The response of the R and VA neurons to stimulation of the relay nuclei as a rule was expressed as excitation. A primary inhibitory response was observed for only two R and three VA neurons. Two types of excitable neurons were distinguished: The first respond to afferent stimulation by a discharge consisting of 5–15 spikes with a frequency of 250–300/sec; the second respond by single action potentials. Neurons of the first type closely resemble inhibitory interneurons in the character of the response. Antidromic responses were recorded from 2.2% of R neurons and 7.8% of VA neurons during stimulation of the relay nuclei. Among the R and VA neurons there are some which respond to stimulation not only of one, but of two or even three relay nuclei. If stimulation of one relay nucleus is accompanied by a response of a R or VA neuron, preceding stimulation of another nucleus leads to inhibition of the response to the testing stimulus if the interval between conditioning and testing stimuli is less than 30–50 msec.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 8, No. 6, pp. 597–605, November–December, 1976.     

Responses of units in the magnocellular part of the medial geniculate body to acoustic and somatosensory stimulation

Responses of 150 neurons in the magnocellular part of the medial geniculate body to clicks and to electrodermal stimulation of the contralateral forelimb were investigated in cats immobilized with myorelaxin. Of the total number of neurons 65% were bimodal, 16.6% responded only to clicks, and 15.4% only to electrodermal stimulation. The unitary responses were excitatory (spike potentials) and inhibitory (inhibition of spontaneous activity). Responses beginning with excitation occurred more frequently to stimulation by clicks than to electrodermal stimulation, whereas initial inhibition occurred more often to electrodermal stimulation. The latent period of the initial spike potentials in response to clicks and to electrodermal stimulation was 5–27 and 6–33 (mean 11.6 and 16.2) msec respectively. Positive correlation was found between the latent periods of spike potentials recorded in the same neurons in response to clicks and to electrodermal stimulation, and also to electrodermal stimulation and to stimulation of the dorsal funiculus of the spinal cord. It is concluded that the magnocellular division of the medial genicculate body is a transitional structure between the posterior ventral nucleus and the parvocellular division of the medial geniculate body, and that in addition, it is connected more closely with the auditory than with the somatosensory system. It is suggested that the somatosensory input into the magnocellular division of the medial geniculate body is formed mainly by fibers of the medial lemniscus.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 10, No. 2, pp. 133–141, March–April, 1978.     

Unit responses of the cat parietal association cortex to stimulation of reticular and anteroventral thalamic nuclei

Responses of 124 neurons in the anterior division of the middle suprasylvian gyrus to stimulation of the reticular (R) and anteroventral (VA) nuclei and the pulvinar (Pulv.) of the thalamus were studied in acute experiments on unanesthetized cats immobilized with D-tubocurarine. Responses of 70 neurons to stimulation of R and Pulv. were investigated. Altogether 51.5% of the cells of this group responded to stimulation of R while 38.6% of neurons responded to stimulation both of R and of Pulv., indicating convergence of afferents from nonspecific and associative nuclei of the thalamus on these neurons. Responses of 54 cells to stimulation of VA and Pulv. were investigated. The tests showed that 72.2% of neurons responded to stimulation of VA and convergence of afferents from VA and Pulv. was found in 29.6% of neurons. As a rule neurons were excited in response to stimulation of R and VA. Inhibition was observed in only one neuron in response to stimulation of R and in six neurons in response to stimulation of VA. The latent period of responses to stimulation of R varied between 2.2 and 37.0 msec, of VA from 6.0 to 35.5 msec, and of Pulv. from 2.1 to 35.0 msec. The length of the latent periods to stimulation of nonspecific and associative nuclei were compared for groups of neurons for which convergence of afferent influences from R and Pulv. or from VA and Pulv. was found. The question of connections of R and VA with the parietal association cortex is discussed.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 5, No. 4, pp. 339–347, July–August, 1973.     

Convergence of signals of various sensory modalities on the neurons of the sensorimotor zone of the rabbit cerebral cortex

The responses of the neurons to electrocutaneous stimulation, light flashes, and clicks in the cortical region of the motor representation of the rabbit forelimb were investigated by means of intra- and quasiintracellular recordings. In unanesthetized animals, in only eight out of 65 neurons did postsynaptic potentials (PSP) with a short (10–30 msec) latent period arise in response to light and sound. In 15 neurons, long latency (50–150 msec) responses to one or both of these stimuli were recorded. In most of the cells, short latency stable responses to stimulation of the contralateral forelimb and unstable long latency responses to light and/or sound, frequently of the nature of an increase in the background "synaptic noise," were observed. Under deep chloralose narcosis, the type of convergence was sharply changed: in most of the neurons, short latency responses to all the stimuli used appeared. However, the picture of convergence differed from that described earlier [5,6] for the motor cortex of the cat under chloralose narcosis. The responses to various stimuli were less similar to one another; the somesthetic modality substantially "predominated" (judging by the stability and nature of the interaction of the response).Brain Institute, Academy of Medical Sciences of the USSR. Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 3, No. 5, pp. 474–483, September–October, 1971.     

Interaction between responses evoked by acoustic and somatosensory stimuli in neurons of the magnocellular part of the medial geniculate body

Interaction between responses to acoustic clicks and to electrodermal stimulation of the contralateral forelimb was investigated in 78 neurons in the magnocellular part of the medial geniculate body of curarized cats. Of this number, 33 neurons responded by discharges both to clicks and to electrodermal stimulation, 25 responded to clicks only, and 20 to electrodermal stimulation only, or to stimulation of the dorsal funiculus of the spinal cord. Conditioning stimulation evoked inhibition of the response to the testing stimulus in 32 of 33 neurons responding by spike discharges to both clicks and electrodermal stimulation. Electrodermal stimulation inhibited responses to clicks in all the neurons tested which responded only to clicks, whereas clicks evoked inhibition of responses to electrodermal stimulation (or to stimulation of the dorsal funiculus) in only four of the 20 neurons which responded to these types of stimulation only. It is suggested that inhibition of excitability arising in neurons of the magnocellular part of the medial geniculate body during interaction between auditory and somatosensory afferent volleys is based on postsynaptic inhibition.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 12, No. 4, pp. 368–374, July–August, 1980.     

Multisensory convergence on neurons of the motor cortex in unanesthetized cats

Postsynaptic potentials (PSPs) of 83 neurons in the motor cortex of unanesthetized cats in response to electrodermal, photic, and acoustic stimulation were investigated by intra-and quasi-intracellular recording methods. Most cells responded to stimulation of at least one limb. About 60% of neurons of the posterior and over 75% of neurons of the anterior sigmoid gyrus responded to stimulation of two (or more) limbs. In 29 of 39 neurons of the anterior and 12 of 44 of the posterior sigmoid gyrus PSPs with a short (less than 50 msec) and stable latent period were evoked by flashes and clicks. On presentation of two somesthetic stimuli complete blocking (if the interval was less than 30–60 msec) or weakening (interval 30–200 msec) of responses to the second (testing) stimulus was observed. On presentation of paired photic (or acoustic) stimuli or paired stimuli of different modalities at various intervals from 0 to 100 msec, the testing response was often potentiated. The character of the responses and their interaction thus differed from those obtained under chloralose anesthesia [6, 7]. It is postulated that under the action of chloralose a system of neurons with strong excitatory feedback is formed in the motor cortex which may respond to stimuli of different modalities by something resembling the "all or nothing" principle.Brain Institute, Academy of Medical Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 3, No. 6, pp. 563–573, November–December, 1971.     

Unit responses in the cat auditory cortex to medial geniculate body stimulation

Responses of 98 auditory cortical neurons to electrical stimulation of the medial geniculate body (MGB) were recorded (45 extracellulary, 53 intracellularly) in experiments on cats immobilized with tubocurarine. Responses of the same neurons to clicks were recorded for comparison. Of the total number of neurons, 75 (76%) responded both to MGB stimulation and to clicks, and 23 (24%) to MGB stimulation only. The latent period of extracellularly recorded action potentials of auditory cortical neurons in response to clicks varied from 7 to 28 msec (late responses were disregarded), and that to MGB stimulation varied from 1.5 to 12.5 msec. For EPSPs these values were 8–13 and 1–4 msec respectively. The latent period of IPSPs arising in response to MGB stimulation varied from 2.2 to 6.5 msec; for 34% of neurons it did not exceed 3 msec. The difference between the latent periods of responses to clicks and to MGB stimulation varied for different neurons from 6 to 21 msec. Responses of 11% of neurons to MGB stimulation, recorded intracellularly, consisted of sub-threshold EPSPs, while responses of 23% of neurons began with an EPSP which was either followed by an action potential and subsequent IPSP or was at once cut off by an IPSP; 66% of neurons responded with primary IPSPs. Neurons responding to MGB stimulation by primary IPSPs are distributed irregularly in the depth of the cortex: there are very few in layers III and IV and many more at a depth of 1.6–2 mm. Conversely, excited neurons are predominant in layer III and IV, and they are few in number at a depth of 1.6–2 mm. It is concluded that the afferent volley reaching the auditory cortex induces excitation of some neurons therein and, at the same time, by the principle of reciprocity, induces inhibition of others. This afferent inhibition takes place with the participation of inhibitory interneurons, and in some cells the inhibition is recurrent. The existence of reciprocal relationships between neurons in different layers of the auditory cortex is postulated.A. A. Bogomolets' Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 4, No. 1, pp. 23–31, January–February, 1972.     

Unit responses of the ventral posterior and ventral lateral thalamic nuclei to electrical stimulation of the thalamic reticular nucleus

A microelectrode investigation was made of responses of 72 physiologically identified neurons of the ventral posterior (VP) and 116 neurons of the ventral lateral (VL) thalamic nuclei to electrical stimulation of the reticular (R) thalamic nucleus. Mainly those neurons of VP and VL (73.7 and 86.2% respectively) which responded to stimulation of the first motor area and nucleus interpositus of the cerebellum responded to stimulation of R; 19.8% of VL neurons tested responded to stimulation of R by an antidromic action potential with latent period of 0.5–2.0 msec and 46.6% of neurons responded by orthodromic excitation; 23% of orthodromic responses had a latent period of 0.9–3.5 msec and 77% a latent period of 4.0–21.0 msec; 19.8% of VL neurons tested were inhibited. Among IPSPs recorded only one was monosynaptic (1.0 msec) and the rest polysynaptic. It is postulated that both R neurons are excitatory and that the inhibition which develops in VL neurons during stimulation of R are connected mainly with activation of inhibitory interneurons outside the reticular nucleus.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 9, No. 5, pp. 477–485, September–October, 1977.     

Neuronal response in nucleus reticularis thalami and neighboring thalamic structures to natural stimulation during chronic experiments on cats

Spike response was investigated in 104 neurons of the nucleus reticularis thalami (R) and adjoining thalamic nuclei to acoustic, tactile, and visual stimuli during chronic experiments on cats. Of the test neurons, 29% responded to acoustic stimulation and 11% showed no preference in relation to different acoustic stimuli. Minimum latencies of response to sounds measured 12–37 msec in excitatory and 18–27 msec in inhibitory cells. Duration of excitation produced by acoustic stimuli reached 50–250 msec; inhibition lasted 27–190 msec. Most cells belonging to this nucleus were excited by different stimuli; the proportion of inhibitory neurons did not exceed 4–10%.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 21, No. 4, pp. 451–461, July–August, 1989.     

Unit responses of the first and second somatosensory cortical areas to peripheral,thalamic, and cortical stimulation

Unit responses of the first (SI) somatosensory area of the cortex to stimulation of the second somatosensory area (SII), the ventral posterior thalamic nucleus, and the contralateral forelimb, and also unit responses in SII evoked by stimulation of SI, the ventral posterior thalamic nucleus, and the contralateral forelimb were investigated in experiments on cats immobilized with D-tubocurarine or Myo-Relaxin (succinylcholine). The results showed a substantially higher percentage of neurons in SII than in SI which responded to an afferent stimulus by excitation brought about through two or more synaptic relays in the cortex. In response to cortical stimulation antidromic and orthodromic responses appeared in SI and SII neurons, confirming the presence of two-way cortico-cortical connections. In both SI and SII intracellular recording revealed in most cases PSPs of similar character and intensity, evoked by stimulation of the cortex and nucleus in the same neuron. Latent periods of orthodromic spike responses to stimulation of nucleus and cortex in 50.5% of SI neurons and 37.1% of SII neurons differed by less than 1.0 msec. In 19.6% of SI and 41.4% of SII neurons the latent period of response to cortical stimulation was 1.6–4.7 msec shorter than the latent period of the response evoked in the same neuron by stimulation of the nucleus. It is concluded from these results that impulses from SI play an important role in the afferent activation of SII neurons.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 8, No. 4, pp. 351–357, July–August, 1976.     

Transformation of the afferent tactile signal into a motor command in the cat motor cortex

Activity of 112 neurons of the precruciate motor cortex in cats was studied during a forelimb placing reaction to tactile stimulation of its distal parts. The latent period of response of the limb to tactile stimulation was: for flexors of the elbow (biceps brachii) 30–40 msec, for the earliest reponses of cortical motor neurons about 20 msec. The biceps response was observed 5–10 msec after the end of stimulation of the cortex with a series of pulses lasting 25 msec. Two types of excitatory responses of the neurons were identified: responses of sensory type observed to each tactile stimulation of the limb and independent of the presence or absence of motion, and responses of motor type, which developed parallel with the motor response of the limb and were not observed in the absence of motion. The minimal latent period of the responses of motor type was equal to the latent period of the sensory responses to tactile stimulation (20±10 msec). Stimulation of the cortex through the recording microelectrode at the site of derivation of unit activity, which increased during active flexion of the forelimb at the elbow (11 stimuli at intervals of 2.5 msec, current not exceeding 25 µA), in 70% of cases evoked an electrical response in the flexor muscle of the elbow.M. V. Lomonosov Moscow State University. Translated from Neirofiziologiya, Vol. 9, No. 2, pp. 115–123, March–April, 1977.     

Responses of caudate neurons to clicks in chronic experiments on cats

Spontaneous and evoked unit activity in response to repeated application of clicks at a frequency of 0.3–2.0 Hz in the caudate nucleus was studied by an extracellular recording technique in chronic experiments on cats. Four types of spontaneous unit activity in the caudate nucleus were distinguished. Altogether 44% of neurons tested responded by changes in spontaneous activity to clicks. Five types of responses of caudate neurons to clicks were discovered: phasic excitation, phasic inhibition, tonic activation, tonic inhibition, and mixed tonic responses; the commonest type was tonic activation. During prolonged stimulation by clicks extinction of the phasic responses was not observed. Complete or partial extinction of tonic responses in the course of frequent repetition of stimulation was observed in 33% of responding neurons. The question of possible convergence of specific and nonspecific influences on caudate neurons is discussed.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 12, No. 1, pp. 28–35, January–February, 1980.     

Responses of caudate neurons to acoustic stimulation in cats

Responses of 141 neurons of the caudate nucleus to acoustic stimuli — tones (500 and 2000 Hz) and clicks of different frequency (0.2 and 0.8/sec) and intensity (75, 80, 95 dB) — were recorded extracellularly in chronic experiments on cats. The responses recorded showed great variability with respect to character (phasic, tonic), structure (one or two phases of excitation), latent periods (from 7.5 to 300.0 msec), and burst discharge frequency (from 90 to 800 spikes/sec). Analysis of averaged poststimulus histograms and graphs of the dynamics of the responses showed that responses of 74% of neurons were much better expressed if less frequent stimuli were used: The regularity of the responses and the number of spikes in each response increased. Responses of neurons also increased and acquired a more distinct temporal structure if the intensity of the clicks increased. The character of responses to clicks and tones differed qualitatively in 17% of neurons studied: Phasic excitation arose in response to clicks, tonic changes in spike activity to tones. The particular features of responses of caudate neurons to acoustic stimulation with different parameters are discussed.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 12, No. 6, pp. 588–595, November–December, 1980.     

Response of neostriatal neurons to direct electrical stimulation of the optic tract and photic stimulation in awake cats

During acute experiments on awake cats the response of 98 neurons belonging to the head and tail of the caudate nucleus to direct electrical stimulation of the optic tract and presentation of photic stimuli was investigated using extracellular recording techniques. Of the test neurons 34.6% responded to stimulation of the optic tract and 36.2% to optic stimulation. Long latency (over 40 msec for the optic tract and over 80 msec for visual stimulation) excitatory responses prevailed in both cases. A small number of cells responded to optic tract stimulation with short latencies of 5–14 msec. Both types of stimulation were presented during investigations of 58 units of which eight were found to respond to both stimuli. The latter varied in their reaction to different stimuli and their response pattern. Findings are discussed in relation to the possible pathways by which visual information reaches the cortical structure under study.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 18, No. 4, pp. 476–485, July–August, 1986.     

Character of evoked responses of the dorsomedial thalamic nucleus to stimulation of the periamygdalar cortex and area amygdaloidea anterior in rats

Characteristics of focal potentials and single unit responses of the dorsomedial nucleus of the thalamus to electrical stimulation of the anterior periamygdalar cortex (APC) and area amygdaloidea anterior (AAA) were compared in acute experiments on rats. Differences were found in the parameters, dynamics, and duration of the recovery cycle of focal potentials in response to stimulation of APC and AAA. Stimulation of APC and AAA was accompanied by changes in the discharges of 26.9 and 19.2% of neurons studied respectively. Four types of unit responses are described: activating (64.3% of responding cells), biphasic activating (14.3%), inhibitory or inhibitory-activating (14.3%), and complex (7.1%). Spontaneous activity was exhibited by 25% of reacting cells. Stimulation of APC was shown to give rise to both shortlatency (12–18 msec) and long-latency (23–66 msec) phasic activating responses of the neurons whereas the latent periods of the analogous responses to stimulation of AAA exceeded 20 msec (from 21 to 136 msec). Unit responses of the second type consisted of a principal phasic response of three or four spikes with mean latent periods of 9–19.1 msec, preceded by a single short-latency (2.9–4.1 msec) spike. Responses of the first two types were characteristic of 92.9 and 64.3% of neurons responding to stimulation of APC and AAA respectively.Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 13, No. 6, pp. 604–611, November–December, 1981.     

Reactions of neurons of the orbitofrontal cortex to stimulation of optic thalamic nuclei

The reactions of 288 neurons of the orbitofrontal cortex (OFC) to stimulation of the posteroventral (VP), ventral anterior (VA), and reticular (R) nuclei, as well as the median center (CM) of the thalamus, were investigated in acute experiments on cats. OFC neurons can be divided into four groups by their reactions to stimulation of thalamic nuclei: 1) those which respond with an increase in the frequency of the discharges to single and serial stimuli with a frequency of up to 20/sec; 2) those which respond doubtfully to single stimuli with a frequency of 4–12/sec; 3) those which respond with inhibition of the background impulses; 4) those which do not respond to stimulation of the nuclei. Stimulation of the thalamic nuclei evoked responses of OFC neurons with a large scatter of the latent period duration. The responses of neurons to stimulation of the VP (mean latent period 19.1±6.1 msec) had the shortest latent period (sometimes less than 3–4 msec). Reactions with a longer latent period developed upon stimulation of the VA (23.8±7.4 msec) and CM (42.8±12.8 msec). The uniqueness of the links of the OFC with the various optic thalamic nuclei is shown in an analysis of the material obtained and possible methods of the activation of the neurons of this region from thalamic structures are discussed.State Medical Institute, Kemerovo. Translated from Neirofiziologiya, Vol. 3, No. 4, pp. 350–358, July–August, 1971.     

Analysis of spike discharge of a neuron population in the cat motor cortex during a conditioned change of posture reflex

Spike responses of area 4 neurons in the projection area of the contralateral forelimb to acoustic stimulation (1 sec), which became the conditioned stimulus after training, and to dropping of the platform beneath the test limb, which served as reinforcing stimulus, were studied in trained and untrained cats. Responses only of those neurons which were activated during a passive movement caused by dropping of the platform were studied. In trained animals the number of these neurons which responded to the conditioned stimulus if a reflex occurred was 100%, and in the absence of conditioned-reflex movements to the conditioned stimulus it was 70%, much greater than the number of neurons responding to the same acoustic stimulus in untrained animals (45%). On peristimulus histograms of responses of the test neuron population in untrained and trained animals to acoustic stimulation (in the absence of movements) only the initial spike response with a latent period of under 50 msec and a duration of up to 100 msec could be clearly distinguished. In the presence of reflex movement multicomponent spike responses were observed: an initial spike response and early and late after-responses linked with performance of conditioned-reflex limb flexion. Early after-responses 100–200 msec in duration, appearing after a latent period of 100–150 msec, were linked to the time of application of the conditioned stimulus, whereas the appearance and duration of late after-responses were determined by the time of onset of conditioned-reflex movement. The magnitude of the neuronal response to reinforcement in trained animals does not depend on the appearance of the conditioned movement.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 17, No. 1, pp. 93–102, January–February, 1985.     

Responses of cat cerebellar cortical neurons to stimulation of the caudate nucleus,globus pallidus,and substantia nigra

Stimulation of the head of the caudate nucleus in cats anesthetized with chloralose and pentobarbital evoked spike responses of the Purkinje cells and other cerebellar cortical neurons in the paramedian lobes, lobulus simplex, and the tuber of the vermis. Phasic responses in the form of simple discharges (on account of activation of the neurons through mossy fibers) appeared mainly after a latent period of 5–12 and 14–20 msec; the latent period of responses consisting of complex discharges (on account of activation of Purkinje cells through climbing fibers) was 5–6, 9–22 msec, or more. Depending on the latent period, the spike responses differed in their rhythm of generation. In response to stimulation of the caudate nucleus with a frequency of 4–6/sec recruiting responses were found. An inhibitory pause was an invariable component of the tonic responses. During stimulation of the globus pallidus responses of the same types (phasic and tonic) appeared as during stimulation of the caudate nucleus, but they differed in the distribution of the neurons by latent period of spike responses. The minimal latent period was 4 msec. Recruiting also was observed during repetitive stimulation of the globus pallidus. During stimulation of the substantia nigra Pukinje cells activated by climbing fibers responded. Evoked complex discharges appeared after a stable latent period of 8.5±0.3 msec. Arguments are put forward regarding the role of the substantia nigra, the globus pallidus, nuclei of the inferior olive, and also the thalamic nuclei in the mechanism of caudato-cerebellar oligosynaptic and polysynaptic connections.N. I. Pirogov Medical Institute, Vinnitsa. Translated from Neirofiziologiya, Vol. 10, No. 4, pp. 375–384, July–August, 1978.     

Conduction of excitation in the cat visual system

Unit responses in area 17 of the visual cortex to stimulation of the lateral geniculate body and optic tract were studied in experiments on unanesthetized cats immobilized with D-tubocurarine. Of the neurons tested, 53.6% responded to stimulation of the lateral geniculate body. In 92% of these cells the responses were orthodromic with latent periods of between 2 and 12.5 msec. Most cells responded with latent periods of 2.0–2.5, 3.0–3.5, and 4.0–4.5 msec, corresponding to latent periods of the components of the electropositive wave of the primary response. Antidromic responses to stimulation of the lateral geniculate body were given by 8% of neurons. The difference between the latent periods of responses of the same visual cortical neurons to stimulation of the optic tract and lateral geniculate body was 0.1–1.8 msec, but for most neurons (55.8%) it was 0.5–1 msec. The histograms of response latencies of visual cortical neurons to stimulation of the above-mentioned formations were found to be similar. It is concluded that the optic radiation contains three principal groups of fibers with conduction velocities of 28.5–16.6, 11.7–8.9, and 7.4–6.0 m/sec, respectively.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 7, No. 6, pp. 589–596, November–December, 1975.     

Postsynaptic potentials of motoneurons evoked by rubrofugal impulsation in the hypoglossal nucleus of the cat

The effect of stimulation of the ipsilateral and contralateral red nuclei on motoneurons of the hypoglossal nucleus was studied in cats anesthetized with chloralose and pentobarbital. In 35 (69%) of the 51 motoneurons tested, PSPs were generated in response to stimulation of the red nuclei by series of 3 to 5 stimuli of threshold strength and with a frequency of 500–600/sec. Of this number, 33 motoneurons responded to stimulation by EPSPs, whose latent periods varied from 3.5 to 14.0 msec (mean value for the ipsilateral red nucleus 5.7±0.75, for the contralateral nucleus 6.8±0.8 msec), whereas two motoneurons responded (after 6.2 msec) by IPSPs. Of the 35 motoneurons responding to stimulation of the red nuclei, stimulation of the lingual nerve evoked EPSPs in 31 and IPSPs in 4 (two of them were inhibited by rubrofugal impulses). IPSPs were generated as a result of stimulation of the lingual nerve in 16 motoneurons which did not respond to rubrofugal impulses.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 10, No. 1, pp. 62–66, January–February, 1978.