Cortical connections of the dorsomedial visual area in prosimian primates.

The dorsomedial visual area (DM) was originally identified in New World owl monkeys as an area rostral to dorsomedial visual area 2 (V2) that is heavily myelinated, contains a complete representation of the visual field, and has a unique distribution of connections with other visual areas. A DM homologue has been proposed in prosimian galagos on the basis of physiological mapping. We determined the pattern of connections of the proposed DM with other cortical visual areas in galagos by placing injections of several different neuroanatomical tracers into DM and locating the resulting label in relation to areal boundaries and modules by using architecture from cytochrome oxidase and myelin preparations. We found that DM is connected with V1, V2, the middle temporal area, and regions of the medial area, the middle superior temporal area, the dorsointermediate area, the ventral posterior area, and the ventral posterior parietal area. Following some injections, label was also found in the fundal superior temporal sulcus area and in the frontal eye field. Connections with V1 were patchy. Although the majority of labeled neurons were in cytochrome oxidase blobs of V1, many labeled neurons were located in interblob regions as well. Similarities in the connections and the architecture of DM of galagos and owl monkeys suggest that the same area has been identified in both groups of primates.