Electrophysiologic relations in the lateral geniculate body

Responses were evoked in the lateral geniculate body (L.G.B.) of "encéphale isolé" cats by single-shock stimulation of either the geniculate body or the optic tract of the other side. Responses to optic tract stimulation were modified following excitability changes in the contralateral L.G.B. due to topical application of strychnine and KCl. Laminar stimulation and recording in different layers (A, A1, and B) suggested the existence of a certain homotopic organization of L.G.B. interconnections. The activity evoked in the L.G.B. was found to be abolished by electrocoagulation of the posterior commissure and intermediate gray matter. These results point to the presence of a transthalamic pathway which might mediate L.G.B. activity to the contralateral visual cortex.     

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.     

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.     

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.     

双眼和单眼视觉剥夺猫外膝体细胞的图形适应

为测定丘脑外膝体细胞的图形适应是否依赖于早期视觉经验,在细胞外记录了双眼和单眼缝合的猫外膝体中断细胞对手工时间运动光栅刺激的反应。在双眼剥夺猫,占６８％的记录到的细胞在３０ｓ内反应下降到稳定值,其平均反应值下降３３％,适应程度较正常猫显著。在单眼剥夺猫,记录到的剥夺眼驱动的和非剥夺眼驱动的细胞中,分别有占５３％和４４％的细胞显示图形适应,两者差别不大。研究表明,早期视剥夺能增强或保持图形适应,提示     

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.