Location and functional definition of human visual motion organization using functional magnetic resonance imaging

In humans, functional imaging studies have found a homolog of the macaque motion complex, MT+, which is suggested to contain both the middle temporal (MT) and medial superior temporal (MST) areas in the ascending limb of the inferior temporal sulcus. In the macaque, the motion-sensitive MT and MST areas are adjacent in the superior temporal sulcus. Electrophysiology has identified several motion-selective regions in the superior temporal sulcus (STS) of the macaque. Two of the best-studied areas include the MT and MST areas. The MT area has strong projections to the adjacent MST area and is typically subdivided into the dorsal (MSTd) and lateral (MSTl) subregions. While MT encodes the basic elements of motion, MST has higher-order motion-processing abilities and has been implicated in the perception of both object motion and self motion. The macaque MST area has been shown to have considerably larger receptive fields than the MT area. The receptive fields of MT cells typically extend only a few degrees into the ipsilateral visual field, while MST neurons have receptive fields that extend well into the ipsilateral visual field. This study tentatively identifies these subregions as the human homologs of the macaque MT and MST areas, respectively (Fig. 1). Putative human MT and MST areas were typically located on the posterior/ventral and anterior/dorsal banks of a dorsal/posterior limb of the inferior temporal sulcus. These locations are similar to their relative positions in the macaque superior temporal sulcus.