THE EFFECT OF VISUAL DEPRIVATION ON THE NUMBER OF CALLOSAL CELLS IN THE CAT IS LESS PRONOUNCED IN EXTRASTRIATE CORTEX THAN IN THE 17 18 BORDER REGION/

It has been shown that neonatal bilateral enucleation and dark rearing in cats markedly reduce the number of callosal cells in the 17/18 bor der region, but whether these deprivation paradigms have the same effe ct in extrastriate cortex is unknown. By comparing numbers of callosal cells retrogradely labeled with horseradish peroxidase in both cortic al regions, we found that enucleation and dark rearing had significant ly less effect in extrastriate cortex. While less than 20% of the comp lement of callosal cells normally found at the 17/18 border region was present in this region in deprived cats, at least 60% of the normal c omplement of callosally-projecting cells was present in extrastriate c ortex of deprived cats. These results suggest that visual experience p lays a less prominent role in the stabilization of callosal connection s in extrastriate visual cortex than in the 17/18 border region.