BINOCULAR INTERACTION IN STRIATE CORTEX OF KITTENS REARED WITH ARTIFICIAL SQUINT

Abstract

In 4 kittens the right medial rectus was severed at about the time of normal eye opening, producing an obvious divergent squint. The animals were raised under normal conditions for periods of 3 months to 1 year. When the 2 eyes were then tested separately no behavioral visual defects were seen. Recordings from the striate cortex were normal, except for a marked decrease in the proportion of binocularly driven cells: instead of about 80% only 20% could be influenced from the 2 eyes. The cortex appeared normal microscopically. In a given penetration there was a marked tendency for cells driven from a particular eye to occur in long uninterrupted sequences. These results suggest that the strabismus caused cells to shift in their ocular dominance, a given cell coming to favor more and more the eye that dominated it at birth, ultimately losing all connections with the non- dominant eye. We conclude that a lack of synergy in the input from the 2 eyes is sufficient to cause a profound disruption in the connections that subserve binocular interaction. Recordings from normal adult cats indicate that besides being grouped according to receptive-field orientation, cells in the striate cortex are grouped by ocular dominance into regions of ipsilateral, contralateral, and mixed dominance. The exaggeration of eye dominance of individual cells, in animals raised with squint, produced an accentuation of these cortical subdivisions.