Electrophysiological investigation of effect of pulvinar stimulation of caudate nucleus neurons that react to visual stimulation

Responses of caudate neurons to electrical stimulation of the afferent input from thepulvinar thalamic nucleus and to visual stimuli of various orientations were studied extracellularly in awake chronic cats. Activation responses dominated among reactions of these neurons. The response latencies have ranged from 4 to 85 msec for units with primary activation and from 20 to 150 msec for inhibited ones. The values are indicative of both rapidly and slowly conducting afferent pathways. A possibility of monosynaptic transmission in thepulvinarcaudate projections is also revealed.Pulvinar stimulation is found to be efficient for a significant (more than 50 percent) number of caudate neurons responding to visual stimuli, including orientation-selective cells. The mode of influences from other structures of the visual system (optic tract, area 17, the Clare-Bishop area) on caudate neurons responding topulvinar stimulation is described. The data are discussed with respect to the possible role of cortical and subcortical projections of the visual system in the creation of sensory specific responses of the caudate nucleus.A. A. Bogomolets Physiology Institute, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 23, No. 5, pp. 520–529, September–October, 1991.     

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.     

Response of caudate nucleus neurons to a photic stimulus at various locations on the visual field in the awake cat

The response of caudate nucleus neurons to presentation of photic stimuli located at varying distances from the fovea centralis was investigated in awake cats. Stimulation of different sites on the visual field below the fovea produced dissimilar reactions in 25 of the 35 (or 71%) of these neurons responding to photic stimulation. This divergence of response indicates that in 6 of these cells (or 17%) the receptive fields in the test area of the visual field bordered on the central area of the latter and 6 neurons (17%) showed reduced sensitivity to the effects of stimuli nearer to the periphery than to the center of the visual field, while 13 units (37%) were receiving qualitatively different information from various sites on the field of vision. On the basis of our findings we deduced that caudate nucleus neurons are involved in the analysis of visual sensory signals.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 18, No. 2, pp. 241–250, March–April, 1986.     

Synaptic transmission in suprasylvian visual cortex is reduced by excitatory amino acid antagonists

The activities of cortical neurones lying in the Clare-Bishop area of the suprasylvian visual region in anaesthetized cats were monitored during the application of cholinergic and amino acid agonists and antagonists, as well as during sequences of light and electrical stimulation. Of those Clare-Bishop cells which could be activated at short latencies by electrical stimuli applied to the contralateral, homologous cortical zone, D-alpha-aminoadipate and 2-amino-5-phosphonovalerate antagonized neuronal responses elicited by electrically evoked synaptic activation and by the presentation of light stimuli. Acetylcholine as well as the excitatory amino acids increased the firing of many of these neurones; however only the amino acid antagonists blocked the commissurally evoked excitations although both types of antagonist reduced the magnitudes of the visually evoked responses. It therefore appears as though the same synaptic transmitter is utilized by cortical commissural afferents as is employed by the cortical ipsilateral projection to the Clare-Bishop area, and furthermore this transmitter is likely to be an excitatory amino acid.     

Changes in the functional characteristics of Clare-Bishop area cells after partial unilateral isolation of the neocortex in cats

Evoked unit activity was investigated bilaterally in neurons of the Clare-Bishop area in cat brain after unilateral severing of the posterior limb of the internal capsule. Cell responses to photic, acoustic, and somatosensory stimuli, also to electrical stimulation of the association areas of the neocortex were investigated. The most rudimentary type of response to a diffuse light flash, electrical stimulation of the forepaw skin, and acoustic stimulation was restored in a proportion of test cells in the operated hemisphere within one week of operating. Sensitivity to visual stimuli increased considerably in cells of the Clare-Bishop area of the intact hemisphere during the first week after the operation. All test cells responded to presentation of light flashes; 80% had receptive fields located to electrical stimulation of the forepaw skin. Seven days after the operation the number of cells responding to photic stimulation fell to 35% and only 17% of cells responded to somatosensory stimuli. This article discusses features of the neuronal compensatory reorganization of the Clare-Bishop area and its role in the recovery of visual function.Institute of Experimental Medicine, Academy of Medical Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 18, No. 2, pp. 180–187, March–April, 1986.     

Neuronal response to sensory stimulation in the cat caudate nucleus

Neuronal response in the caudate nucleus to presentation of a wide variety of visual and other sensory stimuli was investigated in waking cats. Pronounced discrepancies in background activity of unknown origin as well as differing neuronal activity level were noted in adjacent sections of the nucleus. Of the neurons from which readings of response to sensory stimulation could be made, some reacted to presentation of exclusively visual and others to tactile stimuli; a third group responded to a combination of visual and somatic stimulation only. Response could only be produced in cells of all types by a high level of activity in the animal. Visual stimuli attracting the animal's interest proved to be the most effective form of stimulation. Ipsi- and contralateral sides of the animal's body were both represented in the caudate nucleus of each hemisphere. Neuronal response in the caudate nucleus may be compared with that produced by application of similar stimuli in cells belonging to different cortical areas.Institute for Research on Information Transmission, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 22, No. 1, pp. 3–10, January–February, 1990.     

Unit responses of the clare-bishop cortical association area in the cat to photic stimulation

Electrical activity of single unit in the Clare-Bishop visual association area of the cortex was studied in acute experiments on cats immobilized with Flaxedil and after pretrigeminal sections. The method of extracellular recording of action potentials of single units was used. The experimental results showed that 95.5% of cells responding to visual stimulation responded to movement of a spot of light in the receptive field of the neurons, and 55% of the cells responded selectively to the direction of movement. Some neurons responded to movement of a stimulus only when it entered and left the receptive field. About 85.3% of cells responded to a flashing spot of light, and also to a general change in the intensity of illumination of the receptive field. The receptive field of neurons of the Clare-Bishop area in most cases were in the form of stripes with their long axis horizontal. The results point to the important role of this cortical association area in the central analysis of visual information.L. A. Orbeli Institute of Physiology, Academy of Sciences of the Armenian SSSR, Erevan. Translated from Neirofiziologiya, Vol. 10, No. 1, pp. 22–29, January–February, 1978.     

Electrophysiological research into afferent connections of embryonic neocortex allotransplants grafted into the association cortex of adult rats

Grafts of the rat fetal neocortex at the 17–18th day of gestation were placed in the cavity made by aspiration in the primary visual or somatosensory cortex of adult rats. Findings from electrophysiological research performed 3–3.5 months after this transplant showed that neurons of this transplant responded to sensory stimulation specific to the cortical regions replaced by the transplant in 50% of animals. This response was evoked by stimulating local receptive fields displaying a topical organization pattern in a proportion of the animals. Neuronal response in the transplant indicated that the usual field of vision previously existing on the replaced portions of visual cortex had been restored. Electrical stimulation applied locally to a number of brain structures showed that the transplants received afferent inputs from the thalamic nucleus normally projecting to the cortical region replaced by the graft, as well as from homotopic sites on the contralateral cortex. Latencies and time course of neuronal response to stimulating these regions of the host brain resemble those observed in the normal. Afferent inputs from the host brain to cortical transplants thus emulate normal cortical input. Possible mechanisms underlying reinnervation of the grafts are discussed.N. I. Vavilov Institute of General Genetics, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 20, No. 4, July–August, 1988, pp. 448–456.     

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.     

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.     

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

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

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.     

Varying response of caudate neurons to visual stimuli in awake cats

Activity in 62 caudate nucleus neurons produced during presentation of visual stimuli was recorded during experiments on awake cats. Response of a sensory pattern, associated with a photic stimulus falling within a certain section of the visual field was observed in 52% of the neurons tested as against only 11% manifesting motor response related to eye movement guided towards a target. About a quarter of the cells responded to biologically significant stimuli, producing a nonspecific response, i.e., not specifically related to the nature of the visual stimuli presented. Several different response patterns could be recorded from a single unit. A hypothesis that more than one parallel pathway for afferent visual inferences on the caudate nucleus may exist is presented on the basis of findings from this research.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 21, No. 3, May–June, pp. 372–378, 1989.     

Study of the ancient tecto-thalamo-cortical pathway of the visual system in rats

Recording the evoked potentials and neuronal activity, electrophysiological studies have been made on tecto-thalamo-cortical tract in rats. The existence of a system of efferent projections in the superficial, visual layers of the superior colliculi was shown which are diffusely present in the nucleus lateralis posterior (n. LP), indicating low level of morpho-functional organization of this region of the dorsal thalamus in rats. In response to electrical stimulation of the n. LP, in laterocaudal parts of the visual system (fields 17 and 18a of the cortex) the evoked potentials of primary-negative polarity were observed which are associated mainly with the superficial (I--IV) cortical layers. Predominant representation of tecto-thalamo-cortical system in the laterocaudal visual area of the cortex indicates the tendency to separate representation (with respect to cortical areas and cortical layers) of retino-geniculate and retino-tecal visual systems in rats.     

Receptive fields of neurons of cat suprasylvian gyrus studied by stimuli of different colors

Receptive fields of 83 neurons in the Clare-Bishop area and 75 neurons in cortical areas 17 and 18 were studied. Testing receptive fields of neurons in the Clare-Bishop area by stimuli of different colors revealed differences in their structure, in 95% of neurons, depending on stimulus color. The structure of the receptive fields of neurons in areas 17 and 18 remained unchanged under these conditions. It is suggested that the Clare-Bishop area participates in color vision in the cat.I. S. Beritashvili Institute of Physiology, Academy of Sciences of the Georgian SSR, Tbilisi. Translated from Neirofiziologiya, Vol. 14, No. 6, pp. 644–650, November–December, 1982.     

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.     

Response of rabbit visual cortex neurons to direct stimulation by current of different intensities

Response was investigated in 47 rabbit visual cortex neurons to direct intracortical electrical stimulation consisting of single biphasic pulses of increasing intensities within the 150–2,700 µA range. Minimum level for generating all components of response to electrical stimulation remained similar from one neuron to the next, ranging between 150 and 600 µA. Three different patterns of dependence between numbers of spikes at different stages of response and current amplitude were identified: stable, gradual and selective patterns. Percentages of stable dependences were lower for after-discharges in comparison with initial firing (at 11 and 26% respectively) and the proportion of selective dependences were somewhat higher (at 32 and 21%). The selective dependence observed could imply the existence of optimum current levels at which peak neuronal response occurs. At the same time, duration of inhibitory pauses lengthened uniformly in the response of all test neurons during increasing intensity of the electrical stimuli. Findings obtained during this study may have a practical application in matters connected with visual prosthetics in the blind.M. V. Lomonosov State University, Moscow. Translated from Neirofiziologiya, Vol. 21, No. 2, pp. 239–247, March–April, 1989.     

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.     

Hypothalamic control of visual cortical unit activity in rabbits

During the action of an extracellular polarizing current on neurons of the rabbit visual cortex electrical stimulation was applied to various hypothalamic nuclei (preoptic region, anterior hypothalamic region, lateral hypothalamus, mammillary bodies, and posterior hypothalamic nucleus). Hypothalamic stimulation was found to reduce the mean discharge frequency of most visual cortical neurons tested under conditions of anodal polarization, when the initial level of activity is considerably increased, than to a decrease in activity under conditions of cathodal polarization, when the initial level of activity is considerably reduced. The same tendency toward restoration of the initial (spontaneous) level of unit activity after hypothalamic stimulation was discovered when this level was shifted as a result of stimulation by regular flashes. The greatest effect was observed during stimulation of the preoptic region of the hypothalamus. Stimulation of the posterior hypothalamic nucleus was least effective in this respect.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 9, No. 5, pp. 469–476, September–October, 1977.     

Responses of caudate neurons to various visual stimuli in alert cats

Responses of caudate neurons to two kinds of visual stimuli, namely diffuse light and a more local stimulus (a slit of light), oriented in different directions on a screen, were studied in alert cats during natural fixation of the gaze. The number of neurons which responded to local stimulation was several times greater than the number responding to diffuse light. Besides on-responses to local stimulation, a more distinct phase of inhibition of activity during presentation of the stimulus and off-responses also appeared. The latent periods of responses to both kinds of stimulation were commensurate at 40–90 msec for most neurons. Differences in neuronal responses also were found on a change in orientation of the slit. The results are discussed from the standpoint of participation of the caudate nucleus in visual information analysis.