Primary visual cortex projections to extrastriate cortices in enucleated and anophthalmic mice

In the mouse, visual extrastriate areas are located within distinct acallosal zones. It has been proposed that the striate-extrastriate and callosal projections are interdependent. In visually deprived mice, the normal patterns of callosal and striate-extrastriate projections are disrupted. It remains unknown whether visual deprivation affects the topography of V1-extrastriate projections and their relationship with callosal projections. Two anterograde tracers were injected in V1 and multiple retrograde tracer injections were performed in the contralateral hemisphere of intact and enucleated C57BL/6 mice and in ZRDCT/An mice to determine the effects of prenatal and postnatal afferent sensory activity on the topography of V1-extrastriate and callosal projections. Greater topographic anomalies were found in striate-extrastriate projections of anophthalmic than enucleated mice. In enucleated mice, the relationship between striate-extrastriate projections and callosal zones was highly variable. In anophthalmic mice, there was also a greater overlap between these projections. These results suggest that the prenatal afferent sensory activity regulates some aspects of the distribution of V1-extrastriate and callosal projections, in addition to the development of a normal topographic representation in extrastriate areas.