Specificity of projections from wide-field and local motion-processing regions within the middle temporal visual area of the owl monkey

The middle temporal visual area (MT) of the owl monkey is anatomically orga nized with respect to both preferred direction of motion and different type s of center-surround interaction. The latter organization consists of clust ers of neurons whose receptive fields have antagonistic surrounds that rend er them unresponsive to wide-field motion (local motion columns) interdigit ated with groups of neurons whose receptive fields have additive surrounds and thus respond best to wide-field motion (wide-field motion columns). To learn whether the information in these regions remained segregated furth er along the visual pathways, we made injections of retrograde tracers into two visual areas to which MT projects [the medial superior temporal area ( MST) and fundus of the superior temporal sulcus (FST)] and then labeled the wide-field and local organization using 2-deoxyglucose. In complementary e xperiments, we injected anterograde tracers into regions of MT that we had mapped using microelectrode recordings. Injections into both dorsal FST and ventral MST labeled clusters of cell bo dies in MT that were concentrated within wide-field motion columns, whereas injections into dorsal MST labeled neurons predominantly within local moti on columns. Results from the anterograde tracer experiments corroborated th ese findings. The high degree of specificity in the connections reinforces a model of functional organization for wide-field versus local motion proce ssing within MT. Our data support the previously reported division of FST i nto separate dorsal and ventral areas, and they also suggest that MST of th e owl monkey is, like MST of the macaque, functionally organized with respe ct to local versus wide-field motion processing.