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 reveals a system of stripe-like subregions where densely labeled thick and thin stripes and pale interstripes can be recognized. Several lines of evidence suggest that CO stripe-like subregions are associated with functional streams in the visual cortex. In the present study, the distribution of retrogradely labeled callosal cells in V2 and the pattern of CO staining were correlated using tangential sections through the flattened cortex. Spectral and coherency analyses of the callosal and CO patterns were performed to assess quantitatively the degree of spatial correlation between these two patterns. The results showed that labeled callosal cells accumulated along the V1/V2 border and in finger-like bands that protruded up to 7-8 mm into V2. These callosal bands were in register with thick and thin CO stripes, with relatively few labeled callosal cells found in interstripe regions. This finding supports 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, these results extend to interhemispheric pathways the notion of functional specificity currently associated mainly with some visual intrahemispheric pathways.