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.     

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.     

Unit responses of the cat caudate nucleus to cortical stimulation before and after destruction of nonspecific thalamic nuclei

Responses of caudate neurons to stimulation of the anterior sigmoid and various parts of the suprasylvian gyrus were studied in acute experiments on cats. The experiments consisted of two series: on animals with an intact thalamus and on animals after preliminary destruction of the nonspecific thalamic nuclei. Stimulation of all cortical areas tested in intact animals evoked complex multicomponent responses in caudate neurons with (or without) initial excitation, followed by a phase of inhibition and late activation. The latent periods of the initial responses to stimulation of all parts of the cortex were long and averaged 14.5–25.5 msec. Quantitative and qualitative differences were established in responses of the caudate neurons to stimulation of different parts of the cortex. Considerable convergence of cortical influences on neurons of the caudate nucleus was found. After destruction of the nonspecific thalamic nuclei all components of the complex response of the caudate neurons to cortical stimulation were preserved, and only the time course of late activation was modified.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 12, No. 5, pp. 464–471, September–October, 1980.     

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.     

Single unit responses of the reticular and ventral anterior nuclei of the thalamus to electrical stimulation of the centrum medianum

In acute experiments on cats anesthetized with thiopental (30–40 mg/kg, intraperitoneally) and immobilized with D-tubocurarine (1 mg/kg) responses of 145 neurons of the reticular and 158 neurons of the ventral anterior nuclei of the thalamus to electrical stimulation of the centrum medianum were investigated. An antidromic action potential appeared after a latent period of 0.3–2.0 msec in 4.1% of cells of the reticular nucleus and 4.4% of neurons of the ventral anterior nucleus tested in response to stimulation. The conduction velocity of antidromic excitation along axons of these neurons was 1.7–7.6 m/sec. Neurons responding with an antidromic action potential to stimulation both of the centrum medianum and of other formations were discovered, electrophysiological evidence of the ramification of such an axon. Altogether 53.8% of neurons of the reticular nucleus and 46.9% of neurons of the ventral anterior nucleus responded to stimulation of the centrum medianum by orthodromic excitation. Among neurons excited orthodromically two groups of cells were distinguished: The first group generated a discharge consisting of 6–12 action potentials with a frequency of 130–640 Hz (the duration of discharge did not exceed 60 msec), whereas the second responded with a single action potential. Inhibitory responses were observed in only 0.7% of neurons of the reticular nucleus and 4.4% of the ventral anterior nucleus tested. Afferent influences from the relay nuclei of the thalamus, lateral posterior nucleus, and motor cortex were shown to converge on neurons responding to stimulation of the centrum medianum.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 12, No. 1, pp. 36–45, January–February, 1980.     

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 areas to stimulation of the ventroposterior thalamic nucleus

Single unit responses of the first (SI) and second (SII) somatosensory areas to stimulation of the ventroposterior thalamic nucleus (VP) were investigated in cats immobilized with D-tubocurarine. In response to VP stimulation 12.0% of reacting SI neurons and 9.5% of SII neurons generated an antidromic spike. In most antidromic responses of both SI and SII neurons the latent period did not exceed 1.0 msec. The minimal latent period of spike potentials during orthodromic excitation was 1.5 msec in SI and 1.7 msec in SII. Neurons with an orthodromic spike latency of not more than 3.0 msec were more numerous in SI than those with a latency of 3.1–4.5 msec. The ratio between the numbers of neurons of these two groups in SII was the opposite. In SII there were many more neurons with a latency of 5.6–8.0 msec than in SI. EPSPs appeared after a latent period of 1.1–9.0 msec in SI and of 1.4–6.6 msec in SII. The latent period of IPSPs was 1.5–6.8 msec in SI and 2.2–9.4 msec in SII. The relative importance of different pathways for excitatory and inhibitory influences of VP on SI and SII neurons is discussed.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 8, No. 2, pp. 115–121, March–April, 1976.     

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.     

Unit responses in area 5b of the suprasylvian gyrus to stimulation of the posterior lateral thalmamic nucleus

In response to stimulation of the posterior lateral nucleus in unanesthetized cats immobilized with D-tubocurarine an evoked potential consisting of three components with a latent period of 3–5 msec appeared in area 5b of the suprasylvian gyrus. All three components were reversed at about the same depth in the cortex (1500–1600 µ). Reversal of the potential shows that it is generated in that area by neurons evidently located in deeper layers of the cortex and is not conducted to it physically from other regions. Responses of 53 spontaneously active neurons in the same area of the cortex to stimulation of the posterior lateral nucleus were investigated. A characteristic feature of these reponses was that inhibition occurred nearly all of them. In 22 neurons the responses began with inhibition, which lasted from 30 to 400 msec. In 30 neurons inhibition appeared immediately after excitation while one neuron responded by excitation alone. The latent periods of the excitatory responses varied from 3 to 28 msec. The short latent period of the evoked potentials and of some single units responses (3–6 msec) confirms morphological evidence of direct connections between the posterior lateral nucleus and area 5b of the suprasylvian gyrus. Repetitive stimulation of that nucleus led to strengthening of both excitation and inhibition. Influences of the posterior lateral nucleus were opposite to those of the specific nuclei: the posterior ventrolateral nucleus and the lateral and medial geniculate bodies. Stimulation of the nonspecific reticular nucleus, however, evoked discharges from neurons like those produced by stimulation of the posterior lateral nucleus.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 5, No. 5, pp. 502–509, September–October, 1973.     

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

Responses of 189 neurons of the somatosensory cortex to stimulation of the nonspecific reticular (R) and anteroventral (AV) nuclei of the thalamus were studied in cats anesthetized with thiopental and immobilized with tubocurarine. In the series of experiments with stimulation of R and, for comparison, of the specific ventral posterolateral nucleus (VPL), 132 neurons were recorded, of which 22 (16.7%) did not respond to stimulation of these nuclei, 77 (58.3%) responded only to stimulation of VPL, and 33 (25%) responded to stimulation of both VPL and R. In the series of experiments in which AV was stimulated, 57 neurons were recorded. Eight (14.8%) responded to neither stimulus and 25 (43.1%) responded only to stimulation of VPL; 24 responded to stimulation of AV (42.1%), and of these, 10 also responded to stimulation of VPL. A characteristic feature of unit responses in the somatosensory cortex to stimulation of the nonspecific nuclei was the irregularity of the responses and their longer latent period. Only five cells responded sooner to stimulation of the nonspecific nuclei than to stimulation of VPL. Responses of the nonspecific nuclei to stimulation appeared clearly only if the stimulation was repetitive. Preliminary stimulation of R blocks the response to stimulation of VPL during the subsequent 40–60 msec.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol.4, No.4, pp. 384–390, July–August, 1972.     

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.     

Unit responses of the somatosensory cortex of the waking cat to stimulation of the ventro-posterolateral thalamic nucleus

Unit responses in the primary somatosensory projection cortex to stimulation of the ventro-posterolateral thalamic nucleus were investigated by extra- and intracellular recording in chronic experiments on cats. Short-latency spike responses of 71.3% of recorded neurons appeared after not more than 4 msec. It is concluded that activation of neurons in this area of the cortex is chiefly monosynaptic and disynaptic. Besides participating in the initial response to the stimulus, one-quarter of the neurons generated after-discharges 120–314 msec later. These after-discharges are based on rebound after IPSPs and additional synaptic activation. Initial inhibition may appear 1.5 msec after stimulation of the ventro-posterolateral nucleus, evidence against the participation of recurrent collaterals in the formation of these IPSPs.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 5, No. 4, pp. 348–354, July–August, 1973.     

Unit activity of the thalamic associative nuclei in response to peripheral stimulation of different modalities

Responses of 252 neurons of the mediodorsal nucleus (MD) and 329 cells of the pulvinar-posterolateral complex (Pulv-LP) of the thalamus to single and combined stimulation of peripheral receptor systems (visual, auditory, and somatosensory) were investigated in acute experiments on cats anesthetized with a mixture of pentobarbital and chloralose. Three types of responses of these thalamic units to peripheral stimulation were distinguished: quickening of spontaneous activity (Pulv-LP 32.0, MD 20.6%), inhibition (Pulv-LP 21.0, MD 24.2%), and mixed (Pulv-8.8, LP MD 4.0%). No response was found in 37.4% of Pulv-LP neurons and 51.2% of MD neurons. Besides definite similarity in the organization of the two structures, Pulv-LP and MD also had differences. Responses of the neurons to stimulation of peripheral receptors were divided into three groups on the basis of the duration of their latent period: short (under 20 msec), average (21–40 msec), and long (over 41 msec) latent periods. The second group was the largest.Donetsk Medical Institute. Kemerovo Medical Institute. Translated from Neirofiziologiya, Vol. 10, No. 5, pp. 469–477, September–October, 1978.     

Localization of sources of thalamic inputs into the sensorimotor cortex in the rabbit using retrograde axonal transport technique

It was shown that the rabbit sensorimotor cortex received afferent fibers from neurons located in the specific, nonspecific, and association thalamic nuclei using the retrograde axonal transport technique. The distribution, dimensions, and shape of the somata of relay neurons spread through the thalamic nuclei were analyzed. The total number of neurons sending out thalamo-sensorimotor-cortical fibers was calculated and the coordinates of loci with the highest density of these cells in each thalamic nucleus were identified. Multipolar and stellate cells with somata measuring 12–20 µm and 10–15 µm in diameter, respectively, prevailed amongst relay neurons. Amongst the specific nuclei, the majority of afferent fibers are sent out by the ventrolateral, ventral anterior, and anterior ventral nuclei. A comparable number of afferent fibers are sent out by the mediodorsal and paracentral nuclei; these split up among the association nuclei and paracentral nuclei, respectively. It is suggested that afferents from many different groups of thalamic nuclei are essential for the sensorimotor cortex to participate in thalamocortical interaction.Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 19, No. 1, pp. 87–94, January–February, 1987.     

Effects of systemic injection of neuroleptics on neuronal background activity in the cat ventrolateral thalamic nucleus

Background activity was recorded in 272 neurons of the ventrolateral thalamic nucleus before and after systemic haloperidol and droperidol injection at a cataleptic dose using intracellular techniques during chronic experiments on cats in a drowsy condition. Brief burster discharges lasting 5–50 msec and following on at a high intraburst spike rate (of 200–450 Hz) were characteristic of neuronal activity in intact animals. Regular discharges occurred at the rate of 2–2.5 Hz or occasionally 3–4 Hz in 15% of cells. Numbers of neurons with the latter activity pattern rose to 22 and 30%, respectively, following haloperidol and droperidol injection. Both irregular and prolonged (80–300 msec) regular discharges were recorded in one third of the total. A relatively low intraburst spike rate (of 60–170 Hz) was observed in 37% of cells following 10 days' haloperidol injection. These changes are thought to be produced by intensified inhibitory effects on neurons of the thalamic ventrolateral nucleus from the substantia nigra and reticular thalamic nucleus following blockade of dopaminergic and -adrenergic receptors.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 21, No. 5, pp. 675–685, September–October, 1989.     

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.     

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.     

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.     

Modification of evoked unit activity of the dorsomedial thalamic nucleus following destruction of the basolateral amygdala in rats

Neuronal responses of the dorsomedial thalamic nucleus of anesthetized rats to stimulation of the anterior periamygdalar cortex were compared before and after destruction of the basolateral nuclei of the ipsilateral amygdala. After destruction of the afferent inflow from the nuclei of the amygdala a new type of response appeared, in the form of prolonged generation of bursts of spikes, and also a significant decrease in the number of cells with a phasic activation response and an increase in the number of tonically activated neurons. Destruction of the amygdala was shown to lead to an increase in the number of cells of the dorsomedial nucleus with spontaneous activity. The duration of the tonic spike response in animals undergoing the operation was found to be significantly increased from 142.5±42.4 to 375.4±53.8 msec, whereas the parameters of other types of neuronal responses did not differ statistically significantly.Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 16, No. 6, pp. 784–789, November–December, 1984.     

Unit responses of the reticular and ventral anterior thalamic nuclei of cats to orbitofrontal cortical stimulation

Responses of 98 neurons of the reticular (R) and 72 neurons of the ventral anterior (VA) thalamic nuclei to stimulation of various zones of the orbitofrontal cortex were investigated in acute experiments on cats immobilized with D-tubocurarine. Not all zones of this cortex were found to be connected equally closely with R and VA. Most of the R (82.7%) and VA (66.7%) neurons responded to stimulation of the proreal gyrus, and fewest (37.3 and 48.9%, respectively) to stimulation of the posterior orbital gyrus. Among the responding neurons, 85.2–86.3% of R cells and 78.2–81.2% of VA cells were excited by cortical stimulation and the rest were inhibited. Excitation was expressed as the appearance of a single spike or of discharges of varied duration in response to each stimulus. The latent period of the spike responses varied from 0.5 to 55.0 msec and the minimal latent period of the discharges was 0.8 msec and its maximal value over 500 msec. The spike frequency in the discharge was 120–250/sec. Unit responses consisting of spikes with a latent period of under 1.3 msec and, it is assumed, some of the responses with a latent period of under 4.0 msec were antidromic. The axons of some R and VA neurons were shown to form branches terminating in different zones of the orbitofrontal cortex.