Interaction between impulses evoked by stimuli of different modalities in neurons of the parietal associative cortex

In acute experiments on cats anesthetized with chloralose and nembutal interaction between visual, auditory, and electrodermal stimuli in neurons of the parietal association cortex was studied. Two types of interaction were found; the first characterized by inhibition or by inhibition followed by facilitation of the response to the test stimulus, the second by facilitation or by facilitation followed by inhibition of spontaneous impulses. Interaction between stimuli of different modalities was shown to depend on the properties of the neuron. In polysensory neurons ability to interact was much higher than in bimodal or monomodal neurons.M. Gorkii Donetsk Medical Institute. Kemerovo Medical Institute. Translated from Neirofiziologiya, Vol. 8, No. 3, pp. 223–229, May–June, 1976.     

Interaction between visceral,somatic, and visual excitation on single neurons of the lateral geniculate body in cats

Acute experiments on cats anesthetized with pentobarbital and immobilized with diplacin or listhenon showed that visceral and somatic excitation may either facilitate or inhibit single unit activity in the lateral geniculate body evoked by photic stimulation. The manifestations of facilitation were: a modulatory type of enhancement of responses of silent neurons and neurons with a low level of spontaneous activity; enhancement of responses accompanied by simultaneous depression of spontaneous activity — a sensory contrast effect; enhancement of long-latency responses; appearance of a short-latency discharge from cells with an inhibitory response to light; the appearance of responses to light in neurons not responding previously or stabilization of responses in neurons responding to light irregularly. The inhibitory effects were manifested as immediate inhibition of responses, usually long-latency, and the filling up of the inhibitory pauses of the response to light with spikes, leading to a decrease in the signal-noise ratio. Somatic stimulation was more effective and more frequently evoked facilitation of responses to light (in 74% of cells). Similar results were obtained by stimulation of the mesencephalic reticular formation. Visceral excitation gave rise to facilitatory and inhibitory effects to an almost equal degree. The results show that excitation arising as the result of visceral and somatic stimulation affects the conduction of visual information in the neuronal system of the lateral geniculate body.Ivano-Frankovsk Medical Institute. Institute of Experimental Medicine, Academy of Medical Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 5, No. 6, pp. 636–643, November–December, 1973.     

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.     

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.     

Morphological and physiological study of afferent projections of the posterolateral thalamic nucleus in rats

It was shown by the method of retrograde axonal transport of horseradish peroxidase that the posterolateral thalamic nucleus (NPL) in rats receives considerable ascending projections from the superior colliculus (SC), the dorsal part of the lateral geniculate body (LGB), and the pretectal region (PT) and smaller projections from n. ventralis posterior (VP) and n. ventralis lateralis (VL) of the thalamus, the ventral part of LGB, the zona incerta, and anterior hypothalamus. The most marked descending projections run into NPL from area 18A of the cortex and the dentate fascia of the hippocampus, whereas inputs from cortical areas 18, 20, 7, 29c, 17, and 36 are less marked. In electrophysiological experiments with peripheral stimulation of visual, auditory, and somatosensory systems, polysensory convergence and interaction between signals from these systems were studied during isolated and simultaneous presentation of heterosensory stimuli. Of 229 neurons tested, 134 (58.5%) responded to at least one of the stimuli mentioned. Among monomodal neurons (53 of 134) there were some cells which responded to visual (77.4%) and somatic (22.6%) stimulation; neurons which responded only to acoustic stimulation were not found in the nucleus. As far as polymodal neurons (81 of 134) responding to two or three sensory stimuli are concerned, the most effective inputs of these units were visual and somatosensory. Interaction between stimuli acting on polymodal neurons was expressed as mutual inhibition or facilitation of responses; opposite effects could be observed on the various components of these responses.I. M. Sechenov Institute of Evolutionary Physiology and Biochemistry, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 16, No. 2, pp. 168–176, March–April, 1984.     

Unit responses of the cat lateral geniculate bodies to visceral and somatic stimulation

Acute experiments on cats anesthetized with pentobarbital and immobilized with Diplacin or Listhenon showed that electrical stimulation of the vagus, splanchnic, pelvic, and sciatic nerves and also of the mesencephalic reticular formation induces either a prolonged change in the frequency of unit activity or phasic responses of single units of the lateral geniculate body. During stimulation of the visceral nerves tonic changes in unit activity were predominant, whereas phasic responses were found more often during somatic stimulation. Most neurons tested responded to all types of stimulation used and only 15–18% responded only to the specific stimulus: photic stimulation of the receptive field. The results suggest that interaction of visceral, somatic, and sensory-specific excitation takes place on single neurons of the lateral geniculate body.Institute of Experimental Medicine, Academy of Medical Sciences of the USSR, Leningrad. Ivano-Frankovsk Medical Institute. Translated from Neirofiziologiya, Vol. 5, No. 3, pp. 246–252, May–June, 1973.     

Reactions of neurons of orbitofrontal cortex to stimulation of limbic system formations

The reactions of 164 neurons of the orbitofrontal cortex (OFC) to stimulation of the mediodorsal nucleus of the thalamus (MD), the amygdaloid complex, and various sections of the hypothalamus, were investigated in acute experiments on cats. Stimulation of the MD led to the development in OFC neurons of reactions with a short (sometimes less than 6 msec) and stable latent period. Similar reactions were observed upon stimulation of the lateral amygdaloid nuclei. Stimulation of the basal and central nuclei of the amygdala evoked synchronization of the discharges in OFC neurons. Stable responses of OFC neurons developed from nuclei of the hypothalamus only in the lateral region. Stimulation of the other nuclei of the hypothalamus was accompanied by irregular responses or synchronization of the discharges. In an analysis of the material obtained, the functional characteristics of the connections between the structures investigated and OFC neurons were examined.State Medical Institute, Kemerovo. Translated from Neirofiziologiya, Vol. 3, No. 5, pp. 484–490, September–October, 1971.     

Corticofugal influences on segmental responses of lumbar spinal ventral horn interneurons in cats

Experiments on cats using extra- and intracellular recording methods showed that stimulation of the motor cortex of both hemispheres leads to considerable modulation of responses to stimulation of cutaneous and muscular lower limb afferents in spinal ventral horn interneurons in segments L6, 7. Three types of conditioning corticofugal effect were observed: facilitation, inhibition, and facilitation followed by inhibition (biphasic effect), and inhibitory effects predominated. The duration of facilitation of responses did not exceed 30–40 msec. The characteristics of the time course of inhibition varied: in some cases it began with relatively short intervals (8–15 msec), in other cases with an interval of 30–40 msec; its duration was 125–500 msec, or sometimes more. The effect of cortical stimulation on responses to stimulation of various afferent inputs of the same interneuron was shown to differ. The character of the conditioning corticofugal effect correlated with the latent period of segmental responses: facilitation was observed only in responses with a relatively short latent period (under 5 msec); responses with a longer latent period were mainly inhibited. The type of cortical effect also depended on the function performed by the activated afferent input. It is suggested that differential descending control of segmental polysynaptic responses recorded in ventral horn interneurons with wide convergence of afferent influences takes place in the initial stages of the reflex are. The mechanism of this control is discussed.I. P. Pavlov Institute of Physiology, Academy of Sciences of the USSR, Leningrad. Translated from Neiorofizologiya, Vol. 14, No. 6, pp. 563–571, November–December, 1982.     

Unit responses of the medial group of thalamic nuclei to stimulation of the frontobasal regions of the neocortex

In acute experiments on cats anesthetized with pentobarbital and chloralose, single-unit and focal responses of the medial group of thalamic nuclei (mediodorsal, central lateral, paracentral, central medianum, parafascicular) were studied to stimulation of the frontobasal regions of the cortex (proreal, posterior orbital, basal temporal regions). Depending on the number of neurons responding to cortical stimulation and on the length of the latent period of the responses three functionally heterogeneous subdividions of the medial nuclei were distinguished; the parvocellular and magnocellular portions of the mediodorsal nucleus and the intralaminar nuclei with the parafascicular complex. On the basis of responses of neurons activated antidromically by stimulation of the same cortical region and synaptically by stimulation of another region, the concept of the integrative function of nuclei of the medial group, integrating the frontobasal zones of the neocortex with the aid of neuron circuits in which the medial nuclei are included, is argued.M. Gor'kii Donetsk Medical Institute. Translated from Neirofiziologiya, Vol. 9, No. 1, pp. 11–18, January–February, 1977.     

Participation of interoceptive afferent impulses in polymodal responses of superior collicular neurons in the cat

Experiments on immobilized, unanesthetized cats showed that interoceptive afferent impulses reaching the brain via the vagus nerves evoke marked responses in, on average, 43% of superior collicular neurons. Both excitatory and inhibitory effects were observed. The latter were found more often during single stimulation of the vagus nerve. In half of the cases the inhibitory responses were characterized by the development of initial inhibition, clearly limited in time to between 180 and 1700 msec. Changes in spike activity of 60% of units were tonic in character. The onset of phasic responses with an initial period of activation was observed in only 9–11% of neurons. The number of these cells and also the total number of responding neurons were greater than when series of stimuli were applied to the vagus nerve. In individual cells during prolonged repetitive stimulation of the nerve gradual weakening of the responses took place. Somatic stimulation evoked mainly the development of phasic responses of excitatory type. Most of the neurons tested were bimodal and often the temporal structure of their responses was determined by the modality of the stimulus applied. The functional role of the changes discovered in spontaneous activity of superior collicular neurons under interoceptive influences and the central mechanisms of realization of such influences on the activity of the neuronal system in this brain structure are discussed.Ivano-Frankovsk Medical Institute, Ministry of Health of the Ukrainian SSR. Translated from Neirofiziologiya, Vol. 10, No. 6, pp. 590–596, November–December, 1978.     

Neuronal responses of the reticular and anterior ventral thalamic nuclei to stimulation of the thalamic ventrolateral nucleus and motor cortex

Responses of 137 neurons of the rostral pole of the reticular and anterior ventral thalamic nuclei to electrical stimulation of the ventrolateral nucleus and motor cortex were studied in 17 cats immobilized with D-tubocurarine. The number of neurons responding antidromically to stimulation of the ventrolateral nucleus was 10.5% of all cells tested (latent period of response 0.7–3.0 msec), whereas to stimulation of the motor cortex it was 11.0% (latent period of response 0.4–4.0 msec). Neurons with a dividing axon, one branch of which terminated in the thalamic ventrolateral nuclei, the other in the motor cortex, were found. Orthodromic excitation was observed in 78.9% of neurons tested during stimulation of the ventrolateral nucleus and in 52.5% of neurons during stimulation of the motor cortex. Altogether 55.6% of cells responded to stimulation of the ventrolateral nucleus with a discharge of 3 to 20 action potentials with a frequency of 130–350 Hz. Similar discharges in response to stimulation of the motor cortex were observed in 30.5% of neurons tested. An inhibitory response was recorded in only 6.8% of cells. Convergence of influences from the thalamic ventrolateral nucleus and motor cortex was observed in 55.7% of neurons. The corticofugal influence of the motor cortex on responses arising in these cells to testing stimulation of the ventrolateral nucleus could be either inhibitory or facilitatory.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 10, No. 5, pp. 460–468, September–October, 1978.     

Convergence and interaction of reticulofugal and peripheral afferent impulses on caudate neurons in the cat

Extracellular investigations on the activity of 269 caudate neurons during electrical stimulation of the midbrain reticular formation were carried out during chronic experiments on cats. Stimuli of different sensory modalities were used: auditory, mechanical, and visual. A response was observed to both reticular and peripheral stimulation in single neurons. The former produced an orthodromic response in 53% of caudate neurons, notable for its high probability of occurrence. A total of 23% of caudal neurons responded to this type of stimulation and application of stimuli of a single modality, while 14% responded polymodally. An excitatory response pattern prevailed during all types of stimulation. By applying twin stimuli to 100 caudate neurons, a capacity for interaction between reticular and acoustic inputs was discovered. Interaction was similarly observed in neurons which had reacted neither to separate application of both stimuli nor to either of the stimuli in isolation.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 19, No. 1, pp. 101–110, January–February, 1987.     

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.     

Electrophysiological analysis of the functional organization of cortico-cerebellar connections

The effect of stimulation of cortical association (orbito-frontal, parietal) and projection (auditory, sensomotor) areas on the activity of Purkinje neurons of the cerebellar cortex was studied in adult cats anesthetized with pentobarbital, with or without chloralose. These responses were compared with those to peripheral stimuli. Definite similarity was found between the responses of Purkinje cells to different cortical (association and projection) stimuli as regards both the types of responses of the neurons and their ability to respond. No similarity was observed in the responses of Purkinje cells to peripheral (visual, auditory, electrodermal) stimulation. Whereas almost identical numbers of neurons (over 50%) were excited in response to the different forms of cortical stimulation, the ability of the neurons to respond to peripheral stimuli differed considerably: 44.6% of neurons responded to electrodermal stimulation, 34.2% to auditory, and 18.8% to visual.Medical Institute, Kemerovo. Translated from Neirofiziologiya, Vol. 8, No. 5, pp. 483–489, September–October, 1976.     

Responses of neurons of reticular and ventral anterior nuclei of the cat thalamus to afferent stimuli of different modalities

Responses of 146 spontaneously active neurons of the reticular nucleus (R) and of 98 neurons of the ventral anterior (VA) nucleus of the thalamus to electrical stimulation of the skin of the footpads, to flashes, and to clicks were studied in experiments on cats immobilized with D-tubocurarine or myorelaxin. Stimulation of the contralateral forelimb was the most effective: 24.9% of R neurons and 31.3% of VA neurons responded to this stimulation. A response to clicks was observed in only 4.4% of R neurons and 2.4% of VA neurons. Nearly all responding neurons did so by phasic (one spike or a group of spikes) or tonic excitation. Depression of spontaneous activity was observed only in response to electrical stimulation of the skin. Depending on the site of stimulation, it was observed in 2.6–4.3% of R neurons and 1.7–2.1% of VA neurons tested. The latent period of the phasic responses of most neurons was 6–64 msec to electrical stimulation of the contralateral forelimb, 11–43 msec in response to stimulation of the hindlimb on the same side, 10–60 msec to photic and 8–60 msec to acoustic stimulation. Depending on the character of stimulation, 75.1–95.6% of R neurons and 68.7–97.6% of VA cells did not respond at all to the stimuli used. Of the total number of cells tested against the whole range of stimuli, 25% of R neurons and 47% of VA neurons responded to stimulation of different limbs, whereas 16% of R neurons and 22% of VA cells responded to stimuli of different sensory modalities. The functional role of the convergence revealed in these experiments is to inhibit (or, less frequently, to facilitate) the response of a neuron to a testing stimulus during the 40–70 msec after conditioning stimulation.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 7, No. 6, pp. 563–571, November–December, 1975.     

Hypothalamic influences on unit activity in the cat superior colliculus

Experiments on immobilized unanesthetized cats showed that hypothalamic stimulation effectively modified spontaneous unit activity and activity evoked by photic stimulation in the superior colliculus. Long-latency responses, often with a tonic type of formation, were predominant. Meanwhile, definite differences were found in the character of influences from different regions of the hypothalamus. Stimulation of the anterior hypothalamic region and lateral hypothalamus led more frequently to inhibition of spontaneous activity, often expressed as the development of initial inhibition, especially during stimulation of the lateral hypothalamus. Definite modulation of spontaneous activity of cyclic type also developed. Influences from these structures on activity evoked by photic stimulation were chiefly facilitatory and modulating in character. Stimulation of the ventromedial nucleus could produce inhibitory and facilitatory effects equally on activity of tectal neurons, with a tendency for the frequency of manifestation of facilitation to increase when a series of stimuli was used. The mechanisms of triggering and realization of hypothalamic influences on activity in the superior colliculus are discussed.Ivano-Frankovsk State Medical Institute, Ministry of Health of the Ukrainian SSR. Translated from Neirofiziologiya, Vol. 11, No. 6, pp. 560–568, November–December, 1979.     

Negative surface potential shift and responses of neurons and glial cells during tetanic stimulation of the cortical surface

The negative potential shift in response to tetanic stimulation of the surface of the cortex or thalamic nucleus was recorded from the cortical surface in cats lightly anesthetized with pentobarbital. Parallel intracellular recordings were obtained of activity of neurons and glial cells. Glial cells responded to this stimulation by slow depolarization, which, under certain conditions of stimulation, was followed by slow hyperpolarization; hyperpolarization shifts were observed in neurons. Depolarization and hyperpolarization of glial cells, like hyperpolarization of neurons, did not correlate in time with the development of a negative shift of the surface potential. It is postulated that this shift is a response of complex origin involving the participation not only of glial cells, but also of cortical neurons.I. S. Beritashvili Institute of Physiology, Academy of Sciences of the Georgian SSR, Tbilisi. Translated from Neirofiziologiya, Vol. 14, No. 3, pp. 248–253, May–June, 1982.     

Neuronal interaction in the auditory cortex of alert cats

Spontaneous activity of neighboring auditory cortical neurons was derived by glass microelectrodes in chronic experiments on unanesthetized, unimmobilized cats, and the spike trains were subsequently analyzed by computer. Altogether 20 pairs of neurons were tested. The commonest type of interaction (50%) was found to be a common excitatory source, conjectured to be from specific auditory afferents. Interaction of the "common inhibitory source" (5%) and also complex forms of interaction were found. Interaction was absent in only 10% of cases. No direct inhibitory influence of neighboring neurons on one another was observed. The possible causes of absence of a direct inhibitory action are discussed. The most likely cause is absence of marked spontaneous activity in inhibitory auditory cortical neurons.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 16, No. 2, pp. 161–167, March–April, 1984.     

Segmental inhibitory response in the frog spinal cord during orthodromic motoneuron activation

Different types of reflex discharges were produced in various preparations by stimulating the dorsal root of isolated frog spinal cord. These ranged from multiphasic low-amplitude waves to distinctly synchronized monosynaptic response. The discharges were followed by facilitation in the former and deep, protracted inhibition of response to test dorsal root stimulation in the latter. When interstimulus intervals measured 40–50 msec, inhibitory action was less pronounced than at shorter (15–30 msec) or longer (60–100 msec) intervals, thus indicating that at least two types of inhibition were at work, one at an earlier and the other at a later stage. Strychnine at a concentration of 10^–5 M effectively reinforced the former and blocked the latter, while 10^–4 M d-tubocurarine attenuated both types of inhibition substantially. It is concluded that inhibition of response occurs mainly as a result of recurrent activation of inhibitory systems via recurrent motoneuron axon collaterals when frog spinal cord afferents are excited. Intensity of the later (presynaptic) and earlier (postsynaptic) inhibition of reflex transmission is determined by the degree of synchrony in motoneuronal discharge in response to orthodromic stimulation.Institute of Medical Radiology, Academy of Medical Sciences of the USSR, Obninsk, Kaluga Oblast. Translated from Neirofiziologiya, Vol. 19, No. 3, pp. 343–350, May–June, 1987.     

Unit responses of the cerebellar cortex to stimulation of the vagus nerve and nerves of the limbs

Responses of 74 cerebellar cortical neurons to electrical stimulation of the vagus nerve and its gastric branches and also of the limb nerves were recorded extracellularly in experiments on rats anesthetized with chloralose and pentobarbital. Phasic and tonic unit responses were similar to all types of stimulation, but fewer neurons responded to stimulation of the vagus nerve than to stimulation of the limb nerves. Monosensory neurons responding only to visceral stimulation, were not found. Among cells giving a phasic response, some had a short and others a long latent period. The latent period of responses of all types was longer to vagal stimulation than to stimulation of the limb nerves. The maximal frequency of rhythmic responses to vagal stimulation was 8/sec, compared with 16/sec for stimulation of the limb nerves. Tonic responses of the neurons were excitatory, inhibitory, and mixed. The type of unit response could vary depending on the frequency and repetitiveness of the stimuli but was otherwise independent of the type of stimulation.N. I. Pirogov Vinnitsa Medical Institute. I. M. Sechenov Institute of Evolutionary Biochemistry and Physiology, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 4, No. 5, pp. 471–479, September–October, 1972.