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.     

Spontaneous and evoked unit activity in the visual cortex in mutant mice

Spontaneous and evoked unit activity was investigated in the visual cortex of mice with the "ocular retardation" (or/or) mutation, in which the action of the gene is manifested phenotypically by defective development of the optic nerve, with the consequent total blindness of the animals. Control experiments were carried out on inbred C57Br mice. A raised level of spontaneous activity was found in the neurons of the mutant animals and also differences in the distribution of the cells on the basis of the types of their spontaneous activity: A regular type of activity was found 2.5 times more often in the "or/or" mice than in the control group, whereas the proportion of cells with a volley type of discharge was 2.7 times smaller. In addition, visual cortical neurons of the "or/or" mice were more able to respond to acoustic stimulation, when 78% of the responses were tonic in character. Of the unit responses to electrical stimulation of the skin 70% also were tonic, and most were responses of excitation. In 42% of visual cortical neurons of the mutants convergence of heteromodal afferent influences was observed. The functional features described are evidently phenotypical manifestations of the action of the mutant gene on cortical neurons.P. K. Anokhin Institute of Normal Physiology, Academy of Medical Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 8, No. 6, pp. 568–574, November–December, 1976.     

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.     

Comparative effects of amygdala and central gray matter of the midbrain on lateral hypothalamic unit activity

The effect of stimulation of the stria terminalis, the main afferent component of the amygdalo-hypothalmic system, and of the central gray matter and tegmentum of the midbrain on lateral hypothalamic unit activity was investigated in acute experiments on rats. Five types of unit responses were discovered: phasic excitation and inhibition, tonic activation and inhibition, and a biphasic response. In response to stimulation of the stria terminalis and lateral hypothalamus mainly inhibitory responses (62.7%) were recorded. As a result of stimulation of the central gray matter most lateral hypothalamic neurons (87%) were activated. Convergence of influences from the amygdala and tegmentum was observed on 14.4% of responding neurons. The structures had an antagonistic action on most (84.6%) of the lateral hypothalamic neurons tested.Institute of Physiology, Siberian Branch, Academy of Medical Sciences of the USSR, Novosibirsk. Translated from Neirofiziologiya, Vol. 9, No. 1, pp. 25–32, January–February, 1977.     

Electrophysiological investigation of central neurons of the electroreceptor system of the skate

Bioelectrical responses of acoustico-lateral neurons to electrical stimulation of the ampullae of Lorenzini were investigated in acute experiments on the anesthetized Black Sea skateTrigon pastinaca. Three types of responses were found: a primary composite response, prolonged activity, and single unit activity. Excitation of the neurons corresponded to a more marked negative phase, and inhibition to a more marked positive phase of the primary response. The thresholds of the unit responses to adequate electrical stimulation were 10^–9–10^–10 A/mm² and the minimal latent period 20 msec. The spontaneous activity of some neurons clearly depended on the animal's respiration. The character of the response depended on stimulus polarity, as reflected in the appearance of on- and off-responses. A tonic type of response with features of adaptation was predominant. The dependence of some response parameters (latent period of on- and off-responses, firing rate, duration of the contrast interval, response thresholds) on those of the stimulus is analyzed. The mechanisms of these bioelectrical responses are discussed.I. P. Pavlov Institute of Physiology, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol.6, No.1, pp.59–67, January–February, 1974.     

Analysis of evoked discharges in hypothalamic neurons to somatosensory,acoustic, and photic stimulation

Single unit activity in the supramammillary, mammillary, and anterior hypothalamic areas in response to acoustic, photic, and sciatic nerve stimulation was recorded in cats anesthetized with chloralose and immobilized with succinylcholine. In response to sensory stimulation the spontaneous firing rate was increased or decreased, and silent neurons were activated. Evoked potentials of the silent neurons had the shortest latent period to acoustic and somatosensory stimulation (15 msec), and rather longer to photic stimulation (30 msec); in some cases their latent period was 200 msec. Histograms of interspike interval distribution showed a maximum for intervals of up to 50 msec. Histograms of spike distribution relative to the beginning of stimulation showed maximal density between 100 and 200 msec. A high degree of convergence of excitation was found on units of the anterior as well as the posterior hypothalamus. Unit responses in the hypothalamus to sensory stimuli of all three modalities are regarded as being of secondary, nonspecific type.L. A. Orbeli Institute of Physiology, Academy of Sciences of the Armenian SSR, Erevan. Translated from Neirofiziologiya, Vol. 3, No. 6, pp. 592–598, November–December, 1971.     

Corticofugal influences on neurons of the main trigeminal sensory nucleus

The effects of stimulation of the ipsilateral sensomotor cortex were studied on 88 neurons in the region of the main trigeminal sensory nucleus of a cat. The cortex was stimulated via a coaxial electrode by single impulses. Stimulation of the cortex caused the appearance of EPSPs and action potentials in these neurons; a small number of these responses were monosynaptic. The polarity of the impulse applied to the cortex had a significant effect on the magnitude of the latent period of the response and the postsynaptic reaction, which is apparently caused by the stimulation of different types of cortex neurons. Apparently, corticofugal pulsation regulates the level of sensitivity of the trigeminal sensory neurons.A. A. Bogomolets' Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 1, No. 1, pp. 47–53, July–August, 1969.     

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.     

Responses of neurons of different hypothalamic structures to stimulation of tooth pulp and Aß afferents in the cat sciatic nerve

The response of neurons of different hypothalamic structures to stimulation of painful tooth pulp afferents and painless sciatic nerve Aß afferents was investigated during acute experiments on cats. It was found that 80.7%, 81.5%, and 71.4% of neurons of the posterior, tuberal, and anterior hypothalamus respectively, responded to stimulation of the tooth pulp. Shortest latency of response was recorded in the posterolateral hypothalamus. Latency of response was shorter in the lateral than in the medial structures throughout the hypothalamus. A distinct prevalence of excitatory response was found in neurons of the posterior area and an almost equal proportion of excitatory and inhibitory response in neurons of the tuberal and anterior hypothalamus. A high degree of convergence between noxious and nonnoxious somatic afferents were discovered in hypothalamic neurons: 85.8% of those studied responded to stimulation of the sciatic nerve Aß afferents. The comparable unidirectional response pattern of hypothalamic neurons to stimulation of tooth pump painful afferents and painless sciatic nerve Aß fibers point to the nonspecific nature of the response observed in the mainstream population of multisensory hypothalamic neurons. A small population of unimodal nociceptive neurons (14.2%) was found in the hypothalamus. Nociceptive responses of anterior hypothalamic neurons were distinguished by their long refractory phase, lasting 200–500 msec, and their low rate of reproduction during rhythmic stimulation of tooth pulp (1.5–2 Hz). Neuronal organization of the nociceptive hypothalamic afferent system is discussed together with the role of convergent and specific "nociceptive" neurons in the shaping of thalamic regulatory functions.L. A. Orbeli Institute of Physiology, Academy of Sciences of the Armenian SSR, Erevan. Translated from Neirofiziologiya, Vol. 18, No. 2, pp. 171–180, March–April, 1986.     

Reflection of temporal parameters of an optical stimulus in unitary responses of the sensomotor and visual cortex in cats

Unit activity in the visual (area 17) and sensomotor (areas 4 and 6) cortex in response to an optical stimulus up to 1000 msec in duration was investigated by extracellular recording in acute experiments on cats anesthetized with chloralose (70 mg/kg body weight). Comparative analysis of the types of unitary responses and the durations of the intervals of functional changes showed that: 1) The number of neurons generating on-off responses was about 25% in the visual cortex and 100% in the sensomotor cortex; 2) the intervals of functional changes of the neurons were equal in length to the time intervals of on-off discharges; 3) together with a single time range (200–500 msec), for each area studied specific ranges also exist: from 0 to 200 msec for the visual cortex and from 500 msec and more for the sensomotor cortex; 4) the latent period of after-discharge is equal to the duration of the intervals of functional changes. The results were analyzed from the standpoint of reflection of temporal parameters of optical stimuli by neurons of the sensomotor cortex.A. A. Zhdanov Leningrad State University. Translated from Neirofiziologiya, Vol. 7, No. 4, pp. 365–371, July–August, 1975.     

Electrophysiological investigation of medullary neurons connected with lateral line organs of the catfish (Ictalurus nebulosus)

Unit responses in the acoustic-lateral region of the medulla to electrical and mechanical stimulation of the lateral line organs were investigated in acute experiments on curarized catfish. Of the total number of neurons 70% possessed spontaneous activity. An electrical stimulus evoked a tonic response both in spontaneously active and in "silent" cells. Three main types of firing pattern of the neurons were distinguished: fast-adapting, slow-adapting, and grouped. As regards the relation of the neurons to polarity of the stimulus they were subdivided into two groups. The thresholds of unit responses to electrical stimulation varied considerably: from 2.5·10^–9 to 5·10^–12 A/mm². The effect of intensity of the electrical stimulation on unit responses in the medulla is analyzed. The precise dependence of on- and off-responses of each neuron on stimulus intensity of any polarity was determined. The neurons were shown to be sensitive to both electrical and mechanical stimuli. It is postulated that this phenomenon is due to convergence of impulses from electrical and mechanical receptors of the lateral line on the neurons. The properties of the central neurons are compared with those of the peripheral electroreceptor system in catfish.I. P. Pavlov Institute of Physiology, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 5, No. 2, pp. 156–163, March–April, 1973.     

Effect of reticular formation on hippocampal neurons (field CA1)

The reaction of field CA₁ hippocampal neurons to stimulation of the reticular formation (RF) with impulses of different frequencies was investigated in experiments on unanesthetized rabbits. The effect of electrical and sensory stimuli was compared and the effect of reticular stimulation on the sensory responses was determined. With an increase in the frequency of RF stimulation, the number of neurons of field CA₁ responding with inhibition of the activity increases. Multimodal neurons of the hippocampus depend on the reticular input to a greater degree than unimodal neurons. Neurons whose activity does not change in response to the effect of sensory stimuli also do not respond to stimulation of the RF. Neurons responding with inhibitory reactions to sensory stimulation show a higher correlation with the effects of RF stimulation than neurons with activation reactions and, especially those with "complex" responses to the effect of sensory stimuli. In a considerable number of hippocampal neurons the responses to sensory stimuli change in the course of 10–15 min after stimulation of the RF. The role of the RF in the organization of the reactions of hippocampal neurons is discussed.Division of Memory Problems, Institute of Biological Physics, Academy of Sciences of the USSR, Pushchino-on-Oke. Translated from Neirofiziologiya, Vol. 3, No. 3, pp. 227–235, May–June, 1971.     

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.     

Properties of monosynaptic connections between callosal neurons and specific thalamic nuclei

A comparative analysis of monosynaptic afferent and efferent connections of callosal neurons and target neurons of transcallosal fibers with neurons of the specific ipsilateral thalamic nuclei (ventral posterolateral, ventral posteromedial, ventral lateral, and anteroventral) was undertaken on the sensomotor cortex of unanesthetized rabbits, using an electrophysiological method. Differences were demonstrated between callosal neurons and target neurons of transcallosal fibers with respect to monosynaptic inputs from the thalamic nuclei and pathways proceeding toward these structures and (or) entering the pyramidal tract. Among target neurons, compared with callosal neurons, more cells had descending projections (54 and 14%, respectively). Monosynaptic action potentials arose in 22% of target neurons in response to stimulation of specific thalamic nuclei, whereas no such responses occurred in callosal neurons. Projections of target neurons into thalamic nuclei were shown to be formed both by independent fibers and by axon collaterals of the pyramidal tract. It is postulated that the distinctive properties thus discovered indicate significantly greater convergence of influence of thalamic relay neurons on the target neurons; this determines differences known to exist in characteristics of receptive fields and spontaneous and evoked activity of callosal neurons, on the one hand, and of neurons excited synaptically by transcallosal stimulation, on the other hand.Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 17, No. 3, pp. 305–314, May–June, 1985.     

Unit responses of the sensomotor cortex to paired electrical stimuli

Unit responses of the sensomotor cortex to paired electrical stimulation and visual cortex, applied either simultaneously or after various delays (from 0 to 200 msec) depend on the order of application of the stimuli and on the interval between them. If stimulation of the sensomotor cortex was used in a conditioning role the response continued unchanged when the intervals between stimuli were increased to 200 msec. If, however, stimulation of the sensomotor cortex had a testing role interaction was observed between the stimuli so that responses to both first and second stimuli were blocked; this was exhibited most clearly for intervals of 40–80 msec between stimuli. The blocking effect persisted on some neurons with delays of up to 200 msec between stimuli, while the response of others to both the first and the second stimulus was restored.Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 5, No. 6, pp. 628–635, November–December, 1973.     

Role of interoceptive afferent excitation in sensory integration on neurons of the cat visual cortex

Experiments on cats immobilized with diplacin showed that stimulation of the vagus and splanchnic nerves had a significant effect on spontaneous unit activity in area 17 of the cortex. The unit responses most frequently observed were prolonged tonic changes in the discharge frequency. Complex phasic unit responses with stable inhibitory pauses and periods of activation occur less often. The development of phasic responses could begin either with a period of activation or with initial inhibition of activity. As a result of splanchnic nerve stimulation responses of predominantly excitatory type appeared. These also occurred more often in response to somatic stimulation. The degree of recruiting into the responses and the intensity of the responses themselves increased if a series of stimuli was applied to the nerves. The important role of the lateral hypothalamus and mesencephalic reticular formation in the mechanism of the visceral and somatic events observed on visual cortical neurons was demonstrated.Ivano-Frankovsk Medical Institute. Translated from Neirofiziologiya, Vol. 9, No. 4, pp. 361–368, July–August, 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.     

Responses of rabbit visual cortical neurons to intracortical electrical stimulation

Responses of rabbit visual cortical neurons to single and repetitive intracortical electrical stimulation were investigated. The stimulating electrode was located 0.7–1.2 mm away from the recording electrode. Response thresholds to single stimulation were as a rule 150–180 µA, whereas to series of stimuli they were 30–60 µA. The latent period to the first spike averaged 5–15 msec but the probability of the initial discharge was very low, namely 3–6%. With an increase in current intensity the duration of the initial inhibitory pause was increased in half of the neurons responding to it, whereas in the rest it was unchanged. After presentation of series of stimuli spontaneous activity was enhanced for a short time (4–6 sec). In about half of the cells the same kinds of discharge dynamics were observed in response to repetitive stimulation (frequency 0.25 Hz) as in responses to light, but more neurons with sensitization of discharge and fewer "habituating" neurons took part in responses to electrical stimulation. It is postulated that stimulation of a given point of the visual cortex evokes excitation of a local neuron hypercolumn and inhibition of neighboring cell columns.M. V. Lomonosov Moscow State University. Translated from Neirofiziologiya, Vol. 15, No. 4, pp. 412–419, July–August, 1983.     

Convergence of visceral afferent impulses on hypothalamic neurons during vagal and splanchnic nerve stimulation

Responses of posterior and anterior hypothalamic neurons to stimulation of the vagus, splanchnic, and sciatic nerves, and also to photic stimulation were studied by extracellular recording of spike activity in cats anesthetized with chloralose and immobilized with succinylcholine. Most responding neurons of the posterior and anterior hypothalamus did so to stimulation of both vagus and splanchnic nerves. The responses of these polysensory neurons to stimulation of visceral afferents of parasympathetic nerves were identical in sign and mainly excitatory in type. The absence of a reciprocal character of the response to stimulation of "antagonistic" autonomic nerves and the marked polysensory convergence are evidence of the nonspecific "reticular" character of activation of most of the neurons in the posterior and anterior hypothalamus.L. A. Orbeli Institute of Physiology, Academy of Sciences of the Armenian SSR, Erevan. Translated from Neirofiziologiya, Vol. 9, No. 2, pp. 165–170, March–April, 1977.     

Interaction between influences of functionally different cortical areas on caudate neurons in cats

Unit activity in the caudate nucleus evoked by paired stimulation of the anterior sigmoid and middle suprasylvian gyri was studied in acute experiments on cats. Responses in most neurons to testing stimulation of the anterior sigmoid gyrus during the period of inhibition of spontaneous activity evoked by conditioning stimulation of the suprasylvian gyrus were preserved, but in isolated cases they were actually facilitated. Meanwhile conditioning stimulation of the anterior sigmoid gyrus in the period of inhibition depressed responses to testing stimulation of the suprasylvian gyrus. Similar results were obtained in experiments on animals with deep transcortical sections between the sensomotor and parietal regions, ruling out the possibility of interaction between the stimulated zones at the cortical level.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 13, No. 2, pp. 142–148, March–April, 1981.