Binocular units in the lateral geniculate nucleus of chronic cats

Abstract

Summary The effect of monocular and binocular stimulation on cells in the lateral geniculate nucleus was investigated in awake cats with painless head fixation. The cells were stimulated by moving visual patterns presented on a tangent screen. The features of the behavior of the cells were a relatively high level of spontaneous activity and a vigorous response to the moving patterns without any evidence of directional selectivity. Typically, the cells showed either on-, off- or on-off-responses to stimulation with diffuse light. When both eyes were stimulated by the moving patterns, the response varied from cell to cell. According to the form of the response, the cells were classified into 8 types. Depending on receptive field organization and balance of the center-surround influences, responses were either purely excitatory or inhibitory, or combinations of excitation and inhibition. Binocular response was compared with each of two monocular responses in 406 cells. The response was obtained exclusively by stimulation of one eye in 222 cells (54.7%). Binocular interaction occurred in the remaining 184 cells (45.3%). Of these, 85 cells (20.9%) were excited binocularly and various types of binocular interaction, either facilitation, summation or occlusion , occurred. In 70 cells (17.2%), excitation occurred upon stimulation of one eye and inhibition occurred upon stimulation of the other eye, and the response from the dominant eye was markedly suppressed when both eyes were stimulated simultaneously. In 16 cells (3.9%) no response occurred with monocular stimulation of each of the two eyes, but a clear response occurred upon binocular stimulation. Nine cells (2.3%) were activated monocularl, but the input from the non-dominant eye gave a facilitatory influence upon the response and the binocular response was markedly larger than the monocular response. The non-dominant eye gave an inhibitory influence in 4 cells (0.9%). The binocular response was smaller than the dominant eye response. Binocularly activated cells tended to be located in two areas. One area is in the dorsal part of layer A and the other area is below layer A 1 . On the other hand, the cells that were excited by stimulation of one eye and inhibited by stimulation of the other were located predominantly in the two main dorsal layers, A and A 1 .