Behavioral, electrophysiological and morphological studies of binocular competition in the development of the geniculo-corticalpathways of cats

Cats were raised with one eye sutured and with a lesion in the retina of the other eye. In these cats the competitive interaction between the pathways that go to the cortex from each eye was tested by studying the behavioral capacities, the electrophysiological responses and the morphological appearance of the geniculo-cortical pathways. Two parts of the visual system in which no binocular competition was possible were defined. One is the segment that receives inputs from the monocular crescent of the visual field, which has been called the monocular segment. The other is the artificial monocular segment created by the limited lesion of the non-deprived retina, and this has been called the critical segment. In the binocular segments of the visual pathways we found, as have others, that: (1) behaviorally, cats do not respond to objects viewed by the deprived eye; (2) cortical cells tend not to respond to stimulation of the deprived eye; and (3) geniculate cells innervated by the deprived eye grow less than the normally innervated cells. However, we found that the deprived eye is more effective in driving neurons in contralateral than in ipsilateral cortex. Within the monocular and the critical segments of the visual pathways we found: (1) that cats orient appropriately to visual stimulation of the deprived eye, (2) that cortical cells respond to visual stimulation of the deprived eye, and (3) that geniculate cells grow more than the deprived cells in the binocular segment of the nucleus. Thus, the deleterious effects of visual deprivation of one eye can, to some extent, be prevented by damage to the other.