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.     

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.     

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.     

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.     

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.     

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.     

Functional heterogeneity of lateral geniculate body neurons in the rabbit]

Background and evoked activity of LGB units was studied on immobilized and anaesthetized rabbits. Two groups of projection units were revealed, differing by the level of background activity, latencies and mean frequency of discharges in responses to single photic flashes and to electrical stimulation of the optic nerve. It is assumed that these groups of units belong to the slowly and rapidly conducting paths of sensory information transmission in the visual projection system.