Visual Motion Processing in Macaque V2

Summary: In the primate visual system, direction-selective (DS) neurons are critical for visual motion perception. While DS neurons in the dorsal visual pathway have been well characterized, the response properties of DS neurons in other major visual areas are largely unexplored. Recent optical imaging studies in monkey visual cortex area 2 (V2) revealed clusters of DS neurons. This imaging method facilitates targeted recordings from these neurons. Using optical imaging and single-cell recording, we characterized detailed response properties of DS neurons in macaque V2. Compared with DS neurons in the dorsal areas (e.g., middle temporal area [MT]), V2 DS neurons have a smaller receptive field and a stronger antagonistic surround. They do not code speed or plaid motion but are sensitive to motion contrast. Our results suggest that V2 DS neurons play an important role in figure-ground segregation. The clusters of V2 DS neurons are likely specialized functional systems for detecting motion contrast. : Direction-selective (DS) neurons are widely distributed in the primate visual system. Hu et al. examined visual responses of DS neurons in the second largest visual area (V2) in macaque monkeys and demonstrate distinctive response properties of these neurons compared with DS neurons in the well-studied traditional motion area MT. Keywords: macaque, V2, direction selectivity, RF surround, motion contras