INTEROCULAR SUPPRESSION IN THE PRIMARY VISUAL-CORTEX - A POSSIBLE NEURAL BASIS OF BINOCULAR-RIVALRY

In an attempt to demonstrate a physiological basis for the alternating suppression of perception when the two eyes view very different conto urs (binocular rivalry), we studied the responses of neurons in the la teral geniculate nucleus (LGN) and area 17 of cats for drifting gratin gs of different orientation, spatial frequency and contrast in the two eyes. Almost half of the LGN neurons studied exhibited modest inhibit ory interocular interaction, but independent of interocuiar difference s in orientation. Monocularly driven units in layer 4 of area 17 behav ed similarly. However, for the majority of binocular cortical cells, t he response to a grating of optimal orientation in one eye was suppres sed by a grating of very different orientation shown to the other eye, over a wide range of spatial frequency and independent of relative sp atial phase. This interocular suppression exhibits a remarkable non-li nearity: a grating of non-preferred orientation in one eye causes sign ificant interocular suppression only if the neuron is already respondi ng to an appropriate stimulus in the other eye [Sengpiel and Blakemore (1994) Nature, 368, 847-850]. We propose that the switches in percept ual dominance during binocular rivalry depend on interocular interacti ons at the level of binocular neurons of the primary visual cortex, wh ich might involve intracortical inhibition between adjacent ocular dom inance columns. The spontaneous alternations in perceptual suppression that occur during prolonged viewing of rivalrous patterns remain to b e explained, although significant variation in the strength of neurona l suppression in such conditions was occasionally seen.