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.     

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.     

Responses of cortical neurons to viscero-somatic stimulation

Responses of cortical neurons in the posterior sigmoid gyrus of cats anesthetized with chloralose to electrical stimulation of somatic and visceral nerves were recorded. Bimodal viscero-somatic neurons are predominant in this part of the cortex and some of them also respond to light. Besides the polysensory modally-specific neurons it was also possible to distinguish a group of modally nonspecific cells (27%), whose responses to different stimuli did not differ statistically from each other. Simultaneous stimulation of visceral and somatic nerves led to facilitation of activity of the long-latency neurons; this was reflected in a decrease of 10 msec in the latent period of the response and an increase in the number of spikes per discharge.A. A. Zhdanov Leningrad University. Tadjik University, Dushanbe. Translated from Neirofiziologiya, Vol. 3, No. 6, pp. 574–581, November–December, 1971.     

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.     

Organization of afferent inputs of the parietal association (area 7) and Clare-Bishop areas of the cat neocortex

Unit activity was recorded from two parietal areas of the cat neocortex in semichronic experiments. Cell responses to presentation of adequate stimuli of different modalities and to direct electrical stimulation of various cortical zones were studied. About 4% of neurons of the Clare-Bishop area did not respond to visual stimulation. Cells responding to stimuli of different modalities were found in the Clare-Bishop area. A high percentage of cells in this area responded to direct electrical stimulation of area 17. In the association area (area 7) 27% of neurons tested responded to visual stimuli, but only a very small relative number of cells (compared with responding neurons of the Clare-Bishop area) responded to stimulation of the primary sensory areas. Electrical stimulation of area 7 inhibited evoked and spontaneous unit activity in the Clare-Bishop area. The hypothesis that these areas are the association representation of two different sections of the visual system — retino-geniculocortical and retino-tecto-thalamocortical — is discussed.Institute of Experimental Medicine, Academy of Medical Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 13, No. 6, pp. 612–620, November–December, 1981.     

Organization of the visceral afferent representation in the cerebral cortex

In experiments on cats which had been narcotized with chloralose and immobilized with myo-relaxants, we have studied cerebral cortical responses to stimulation of the visceral system. A peculiarity of the visceral afferent representation is the fact that the convergence of visceral and dermomuscular impulses is achieved with predominance of somatic signals in the cortical zones of visceral representation, with the exception of the focus of maximal activity (FMA). A second peculiarity is the fact that the visceral afferent systems develop habituation to prolonged stimulation. The principles of this development are similar to the general principles described in the literature for other sensory systems.     

Habituation of direct cortical responses in cats

Gradual diminution of direct responses of various cortical areas was studied in acute experiments on cats under barbiturate anesthesia. During repetitive stimulation of the surface of cortical association areas these responses underwent all changes characteristic of the habituation phenomenon. Direct cortical responses in primary projection areas were distinguished by great stability, and habituation was absent in this case. After neuronal isolation of an island of projection cortex, habituation of responses began to develop there just as in the cortical association areas. The possible causes of differences between changes in direct cortical responses in different areas are discussed. It is suggested that projection areas receive strong activating influences from deep brain structures, which exert a sensitizing effect on the direct responses.I. S. Beritashvili Institute of Physiology, Academy of Sciences of the Georgian SSR, Tbilisi. Translated from Neirofiziologiya, Vol. 13, No. 3, pp. 241–246, May–June, 1981.     

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.     

Investigation of habituation reaction of neurons of the cat motor cortex

The neuronal and total surface activity of the cortical representation of the motor analyzer in the region of the posterior sigmoid gyrus of the cat brain in response to rhythmical light, sound, and electrical stimuli and their complexes was analyzed. Two groups of neurons were found, of which the first is characterized by a gradual decrease in the number of peaks in the response and by their subsequent disappearance and the second by the absence of a discharge in response to stimulation and by its development before the application of the next stimulus. The first group was comprised of neurons which do not have background activity and the second was made up of neurons with a background activity of 0.4–3.7 imp/sec. This reorganization of the activity of cortical neurons in response to rhythmical stimulation is considered to be a habituation phenomenon.A. A. Zhdanov Leningrad State University. Translated from Neirofiziologiya, Vol. 3, No. 3, pp. 245–251, May–June, 1971.     

Some characteristics of unit activity in the frontal cortex of alert monkeys

Spontaneous activity of frontal cortical neurons (middle part of sulcus principalis) and their responses to stimuli of different biological significance were studied in alert monkeys. The region studied is characterized by a lower level of spontaneous activity than the motor cortex. Fluctuations in the level of spontaneous activity are connected with changes in the experimental situation. Two types of unit responses were distinguished to repetitive stimulation: preservation of responses and habituation. The type of unit response depends on the relationship of the stimuli to the animal's motivational sphere.A. A. Ukhtomskii Physiological Research Institute, A. A. Zhdanov Leningrad State University. Translated from Neirofiziologiya, Vol. 12, No. 1, pp. 3–12, January–February, 1980.     

Reticular structures and reticulospinal pathways participating in the initiation and inhibition of spino-bulbo-spinal activity

Reflex discharges in intercostal nerves and activity of reticulospinal fibers of the ventral and lateral funiculi, evoked by stimulation of the reticular formation and of the splanchnic and intercostal nerves were investigated in cats anesthetized with chloralose (50 mg/kg). Brain-stem neuronal structures participating in the "relaying" of spino-bulbo-spinal activity were shown to lie both in the medial zones of the medullary and pontine reticular formation and in its more lateral regions; they include reticulospinal neurons and also neurons with no projection into the spinal cord. Structures whose stimulation led to prolonged (300–800 msec) inhibition of reflex spino-bulbo-spinal activity were widely represented in the brain stem, especially in the pons. Analogous inhibition of this activity was observed during conditioning stimulation of the nerves. Reticulospinal fibers of the ventral (conduction velocity 16–120 m/sec) and lateral (17–100 m/sec) funiculi were shown to be able to participate in the conduction of spino-bulbo-spinal activity to spinal neurons. In the first case fibers with conduction velocities of 40–120 m/sec were evidently most effective. Evidence was obtained that prolonged inhibition of this activity can take place at the supraspinal level.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Institute of Normal and Pathological Physiology, Slovak Academy of Sciences, Bratislava, Czechoslovakia. Translated from Neirofiziologiya, Vol. 8, No. 4, pp. 373–383, July–August, 1976.     

Effect of direct and transcallosal stimulation on inhibition of unit activity in the cat association cortex

Inhibition of association cortical neurons (in the form of inhibition of spontaneous activity or of IPSPs) during direct and transcallosal stimulation was studied in cats immobilized with muscle relaxants. The duration of inhibition of stimulation and the number of stimuli. With an increase in the strength of stimulation inhibition deepened to a certain level for a particular neuron, after which it could be further lengthened with an increase in the number of stimuli. In the case of repeated stimulation by volleys of stimuli, very prolonged inhibition developed gradually in the neurons, during which spontaneous activity was inhibited for 2–5 sec. The duration of the IPSP depended on the intensity of stimulation and number of stimuli and its amplitude depended on the intensity and frequency of stimulation and on the number of stimuli. In some cases the amplitude of the IPSP continued to rise after a short volley of stimuli, even after the end of stimulation. An increase in the number of stimuli in the volley lengthened the IPSPs, but their amplitude remained constant throughout the period of stimulation. Prolonged inhibition (up to a few seconds) was connected with the development of a hyperpolarization postsynaptic potential in the neurons. It is suggested that neurons exerting a monosynaptic inhibitory influence on cells of the association cortex may be located in the opposite hemisphere.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 13, No. 2, pp. 133–141, March–April, 1981.     

Neuronal responses of a chronically isolated slab of auditory cortex to intracortical stimulation during paroxysmal electrical activity in cats

Responses of 155 neurons 3 weeks after neuronal isolation of a slab of auditory cortex (area AI) to single intracortical stimulating pulses at the level of layer IV were studied in unanesthetized, curarized cats during paroxysmal electrical activity evoked by series of high-frequency (10–20 Hz) electrical stimulation by a current 2–5 times above threshold for the direct cortical response. In response to such stimulation a discharge of paroxysmal electrical activity, lasting from a few seconds to tens of seconds, appeared in the slab. As a rule it consisted of two phases — tonic and clonic. This indicates that cortical neurons can form both phases of paroxysmal cortical activity. Depending on behavior of the neurons during paroxysmal electrical activity and preservation of their ability to respond to intracortical stimulation at this time, all cells tested in the isolated slab were divided into four groups. Their distribution layer by layer and by duration of latent periods was studied. Two-thirds of the neurons tested were shown to generate spike activity during paroxysmal discharges whereas the rest exhibited no such activity. A special role of neurons in layer II in generation of paroxysmal activity in the isolated slab was noted. The view is expressed that at each moment functional neuronal circuits, independent of each other, exist in the slab and also, evidently in the intact cortex, which can interact with one another when conditions change.I. I. Mechnikov Odessa State University. Translated from Neirofiziologiya, Vol. 16, No. 1, pp. 3–11, January–February, 1984.     

Organization of neurons responding to photic stimulation in the Clare-Bishop area in cats

Neuronal organization in the Clare-Bishop cortical association area was studied by consecutive vertical penetration of an electrode and analysis of unit responses to photic stimulation during each penetration. Activity of one or two neurons was recorded during 131 penetrations, and activity of over 3 neurons responding to photic stimulation (visually driven) during 55 penetrations. In 8 of the 55 penetrations all neurons discovered in each had identical characteristics; this type of organization corresponded most of all to the columnar organization of the cortical neurons. In 24 penetrations the neurons were arranged in groups: two or three neurons of one type intermingled with neurons of other types. In 18 penetrations considerable overlapping of the receptive fields of neurons in the same column was observed. A chaotic distribution of neurons with different characteristics was found in 5 penetrations. It is suggested that the organization of neurons in the Clare-Bishop area in columns as functional units of cortical structure is not the principal type of their organization.L. A. Orbeli Institute of Physiology, Academy of Sciences of the Armenian SSR, Erevan. Translated from Neirofiziologiya, Vol. 11, No. 4, pp. 297–302, July–August, 1979.     

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.     

Crossed and uncrossed afferent inputs of mesocerebral neurons of the mollusk Planorbis corneus

Experiments on the isolated ganglionic ring of the freshwater molluskPlanorbis corneus showed that more neurons (30%) in the ipsilateral mesocerebrum respond to stimulation of the left cerebral nerves than to stimulation of the opposite nerves (13%). A similar picture is observed for neurons of the right mesocerebrum, except that 11% of neurons respond to activation of the left cerebral nerves compared with 39% to stimulation of the ipsilateral right cerebral nerves. Ipsilateral connections of nerve of the visceral complex of ganglia are more clearly defined, as is exemplified by the left pallial nerve, during stimulation of which 68% of neurons in the ipsilateral mesocerebrum were activated, compared with 8% in the contralateral right mesocerebrum. Afferent fibers running in the visceral nerves cross at the level of the abdominal ganglion and not of the cerebral commissure, as might be expected from the structure of the ganglionic ring. The mesocerebral neurons themselves do not form synaptic connections between the mesocerebra, and excitation reaching one of them does not therefore induce any effects in the other.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 5, No. 6, pp. 571–575, November–December, 1973.     

Unit responses in the anterior and posterior hypothalamus to stimulation of the splanchnic and sciatic nerves and to photic stimulation

By extracellular recording of spike discharges the sensory properties of neurons of the anterior and posterior regions of the cat hypothalamus were studied during stimulation of the splanchnic and sciatic nerves and during photic stimulation. Hypothalamic neurons were shown to be characterized by wide convergence of heterosensory excitation: 68% of spontaneously active hypothalamic neurons responded to somatovisceral and photic stimulation. Some posterior hypothalamic neurons responded to somatovisceral stimulation but not to photic stimulation. Neurons responding only to photic stimulation were found in the anterior hypothalamus; no neurons responding only to visceral stimulation were found in the hypothalamus. Total convergence of somatic and visceral afferentation of neurons of the posterior and anterior hypothalamus was observed. Mostly responses of phasic type were obtained to stimulation of all modalities. The study of the quantitative ratio between responses of excitatory and inhibitory types showed that the former predominate. The principles governing the functional organization of hypothalamic afferent systems are discussed.Academician L. A. Orbeli Institute of Physiology, Academy of Sciences of the Armenian SSR, Erevan. Translated from Neirofiziologiya, Vol. 8, No. 3, pp. 276–282, May–June, 1976.     

Unit responses in the cat auditory cortex to electrical stimulation of nerve fibers innervating receptor cells in different parts of the organ of corti

Responses of 200 primary auditory cortical neurons to electrical stimulation of nerve fibers in different receptor zones of the cochlea were studied in cats anesthetized with pentobarbital. Under the influence of paired stimulation, after the response to the conditioning stimulus a state of prolonged (from 4 to 200 msec) refractiveness to the second stimulus developed in all the neurons tested. This long-lasting inhibition of unit activity was due to inhibition developing in the thalamus and the auditory cortex itself. The intensity and duration of excitation and inhibition in the cortical projection focus were maximal when the center of the receptive field was stimulated and decreased when the stimulus shifted from the center to the periphery. The region of the receptor surface of the cochlea to stimulation of which the auditory cortical neurons respond by an action potential is much narrower than the region whose electrical stimulation depresses the discharge of these neurons.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 14, No. 4, pp. 418–425, July–August, 1982.     

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.     

Spinal and spino-bulbo-spinal neuronal mechanisms of transmission of somatomotor and visceromotor reflexes in the thoracic spinal cord

Early (spinal) and late (spino-bulbo-spinal) responses of interneurons in segments T9–10 to stimulation of the splanchnic and intercostal nerves and the dorso-lateral and ventral funiculi of the spinal cord (at the C3 level) were investigated in experiments on cats anesthetized with chloralose. The experiments showed that interneurons activated by spinal and spino-bulbo-spinal mechanisms differ in their distribution in the dorso-ventral plane of the spinal cord. Cells of layers I–V were excited by spinal pathways only, but those of layers VII and VIII by both spinal and spino-bulbo-spinal or only by the latter. Spino-bulbo-spinal effects were evoked in interneurons by both somatic and visceral afferent waves. A conditioning spino-bulbo-spinal wave evoked deep and prolonged inhibition of late activity induced by somatic or visceral afferent impulses. Early (spinal) activity was inhibited only partially under these circumstances. This inhibition was shown to take place with the participation of supraspinal structures. The possible types of spinal and supraspinal mechanisms of inhibition of early and late activity in spinal neurons are discussed.Institute of Normal and Pathological Physiology, Slovak Academy of Sciences, Bratislava, Czechoslovakia. A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev, USSR. Translated from Neirofiziologiya, Vol. 5, No. 4, pp. 392–400, July–August, 1973.