Reciprocal connections between the striate cortex and extrastriate cortical visual areas in the rat.

Following injections of horseradish peroxidase (HRP) in the striate cortex of rats, a precise topographical correspondence between extrastriate cortical fields of anterograde and retrograde label was observed. The arrangement of these extrastriate labeled fields corresponds closely to the previously reported division of the peristriate cortex into multiple visual areas, suggesting that each of these areas is reciprocally connected to striate cortex. Cortical layers II--VI participate in this reciprocal connection.