THE DISTRIBUTION OF CALLOSAL CONNECTIONS CORRELATES WITH THE PATTERN OF CYTOCHROME-OXIDASE STRIPES IN VISUAL AREA V2 OF MACAQUE MONKEYS

In visual area V2 of monkeys, cytochrome oxidase (CO) histochemistry r eveals a system of stripe like subregions where densely labeled thick and thin stripes and pale interstripes can be recognized. Several line s of evidence suggest that CO stripe-like subregions are associated wi th functional streams in the visual cortex. In the present study, the distribution of retrogradely labeled callosal cells in V2 and the patt ern of CO staining were correlated using tangential sections through t he flattened cortex. Spectral and coherency analyses of the callosal a nd CO patterns were performed to assess quantitatively the degree of s patial correlation between these two patterns. The results showed that labeled callosal cells accumulated along the V1/V2 border and in fing er-like bands that protruded up to 7-8 mm into V2. These callosal band s were in register with thick and thin CO stripes, with relatively few labeled callosal cells found in interstripe regions. This finding sup ports the notion that the distribution of callosal connections in the visual cortex is dictated not only by the topography of visual areas, but also by the arrangement of cortical functional streams. Further, t hese results extend to interhemispheric pathways the notion of functio nal specificity currently associated mainly with some visual intrahemi spheric pathways.