Receptive field dynamics of neurons in the cat visual cortex and lateral geniculate body

Spike responses of single neurons in the primary visual cortex and lateral geniculate body to random presentation of local photic stimuli in different parts of the receptive field of the cell were studied in acute experiments on curarized cats. Series of maps of receptive fields with time interval of 20 msec obtained by computer enabled the dynamics of the excitatory and inhibitory zones of the field to be assessed during development of on- and off-responses to flashes. Receptive fields of all cortical and lateral geniculate body neurons tested were found to undergo regular dynamic reorganization both after the beginning and after the end of action of the photic stimulus. During the latent period of the response no receptive field was found in the part of the visual field tested, but later a small zone of weak responses appeared only in the center of the field. Gradually (most commonly toward 60–100 msec after application of the stimulus) the zone of the responses widened to its limit, after which the recorded field began to shrink, ending with complete disappearance or disintegration into separate fragments. If two bursts of spikes were generated in response to stimulation, during the second burst the receptive field of the neuron changed in the same way. The effects described were clearly exhibited if the level of background illumination, the intensity of the test bars, their contrast with the background, duration, angles subtended, and orientation were varied, although the rate and degree of reorganization of the receptive field in this case changed significantly. The functional importance of the effect for coding of information about the features of a signal by visual cortical neurons is discussed.Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 14, No. 6, pp. 622–630, November–December, 1982.     

“Regular” visual receptive fields of neurons of the cat lateral geniculate body

The spatial organization of receptive fields (RF) of neurons was studied in the lateral geniculate body (LGB) of cats with pretrigeminal transection of the brainstem (without general anesthesia). Using systematic point testing of the entire RF area and adjacent regions, the RF configuration and distribution of the response types for a stable flickering stimulus throughout the RF area were determined. Only 40% (64 units of 160 studied) LGB neurons had simple RF configuration. Such RF of ellipsoid or round shape were called regular receptive fields, RRF. Most RRF (51, or about 80%) demonstrated spatially homogeneous organization with similar-type (on, off, oron-off) responses to stimulation of the entire RF area. The RRF of 13 neurons, i.e., about 20%, included subfields with qualitatively different responses to application of a stable flickering light spot. The position of subfields was asymmetrical in 8 neurons (13%), while a nearly concentric RF arrangement, with the center surrounded by an antagonistic area, was found only in 5 units (7%) with RRF. Nearly all neurons with heterogeneous RRF demonstrated directional selectivity to moving stimuli.Neirofiziologiya/Neurophysiology, Vol. 27, No. 5/6, pp. 413–424, September–December, 1995.     

Sensitivity of the cat lateral geniculate body neurons to orientation of the brightness gradient vector

A new property of visual neurons: their sensitivity to orientation and the vector brightness gradient, was revealed and described. Receptive fields of the lateral geniculate body neurons in the cat have preferred orientation maximum reaction (average mean of orientation sensitivity coefficient--0.55 +/- 0.20). The preferred orientation mainly has a radial or tangential trend in the visual field. Temporal characteristics of the neuronal responses were analysed. A role of inhibition processes in the orientation sensitivity is discussed.     

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.     

Characteristics of residual neurons during retrograde degeneration in the cat lateral geniculate body

The dynamics of structural and functional characteristics of residual neurons in the degenerating lateral geniculate body was studied in cats during the 4–12 months after division of all cortico-subcortical projection connections, including axons of relay cells of the lateral geniculate body [9]. Spontaneous and evoked activity of the residual cells, their number, and also the dimensions of the cell bodies were investigated. With lengthening of the postoperative period a decrease in the number of cells of the lateral geniculate body responding to photic stimulation and also destruction of their receptive fields were observed; 12 months after the operation the residual neurons of the lateral geniculate body lose their sensitivity to photic stimulation. Morphological investigation revealed a progressive reduction in the number of neurons in the degenerating lateral geniculate body and predominance of small neurons among them. The nature of interneuronal relations in the lateral geniculate body are discussed on the basis of the results.Research Institute of Experimental Medicine, Academy of Medical Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 9, No. 6, pp. 575–582, November–December, 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.     

Inhibitory zones of receptive fields of the lateral geniculate body and visual cortex of the cat

Unit responses to moving strips were investigated. The organization of the inhibitory zones in the receptive fields of the lateral geniculate body and visual cortex of the cat was compared. The response in the receptive field of the lateral geniculate body was inhibited only during simultaneous stimulation of the excitatory and inhibitory zones of the field. Stimulation of the inhibitory zone in the receptive field of the visual cortex was effective for a long time (several hundreds of milliseconds) after stimulation of the excitatory zone. The inhibitory zones of the simple and complex receptive fields of the visual cortex differed significantly. An increase in the width of the strip above the optimal size reduced the inhibitory effect in the complex fields. This was not observed in the simple receptive fields. The functional and structural models of the receptive field of the visual cortex are discussed.I. P. Pavlov Institute of Physiology, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 5, No. 2, pp. 201–209, March–April, 1973.     

Analysis of unit activity in the cat lateral geniculate body

Spontaneous and evoked single unit activity of lateral geniculate body neurons was recorded extracellularly in acute experiments on cats. Eight groups of neurons differing in the durations of the minimal and mean interspike intervals of spontaneous unit activity, and in the latent period and duration of the first volley of spikes of evoked activity, were distinguished by analysis of the data. On the basis of this classification a scheme for interaction between neurons of the lateral geniculate body is suggested.Institute of General Pathology and Pathological Physiology, Academy of Medical Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 10, No. 1, pp. 30–37, January–February, 1978.     

Dependence of functional organization of receptive fields of the cat lateral geniculate body on visual stimulus contrast

The spatial organization of receptive fields of the lateral geniculate body in response to visual stimuli with different degrees of contrast was studied in cats. During variation of contrast changes in organization of the central zone were found to take place in some receptive fields. Inside the central zone of the receptive field as revealed by the use of low stimulus contrasts, an additional inhibitory ring appears in response to a stimulus of high contrast. The weighting function of the central zone of the receptive field becomes variable in sign. The role of this phenomenon in transmission of information on high spatial frequencies (increase in visus) at high contrasts is discussed.I. P. Pavlov Institute of Physiology, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 16, No. 6, pp. 789–796, November–December, 1984.     

Corticofugal control of unit responses of the cat lateral geniculate body

Acute experiments on anesthetized cats showed that blocking the projection connections of the cortex unilaterally increased the number of lateral geniculate neurons which generated long-latency phasic responses and the number of spikes in the responses of single neurons. Unit responses were monophasic more frequently in the lateral geniculate body on the side of the operation than in the same structure on the opposite side. On the basis of these results a hypothesis is developed to explain the mechanisms of monomodal descending cortical effects in microsystems of neurons of the lateral geniculate body.Institute of Experimental Medicine, Academy of Medical Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 5, No. 4, pp. 367–374, July–August, 1973.     

Cortical control of the afferent flow in the cat lateral geniculate body

Single unit responses in the dorsal lateral geniculate body to stimulation of the optic chiasma (testing) and area 17 (conditioning) of the visual cortex were studied in unanesthetized cats immobilized with tubocurarine. Two types of unit responses were found: P-responses (considered to be of relay, or principal, cells) and I-responses (considered to be of interneurons), whose parameters differed distinctly. Interaction between stimulation of the visual cortex and optic chiasma consisted of depression of the ability of the P cells of the nucleus to respond to testing stimulation. It is suggested that cortical influences on stimulus conduction by P cells of the nucleus is based on postsynaptic inhibition with the participation of interneurons.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 13, No. 6, pp. 563–570, November–December, 1981.