Temporal property of single-cell activity in response to motion-defined shapes in monkey dorsal and ventral cortical areas.

In the primate brain, shape and motion are considered to be separately processed in the ventral and dorsal visual cortical areas, respectively. However, to achieve shape perception with a motion cue, shape and motion cannot be processed exclusively in separate cortical areas. Interactions between ventral and dorsal cortical areas are required, and yet, the neural mechanisms underlying motion-defined shape perception remain unclear. Here, we assessed the temporal properties of single-unit activity recorded from V4, the middle temporal area, and the anterior superior temporal sulcus while monkeys discriminated shapes defined by motion and luminance cues. Visual response latencies of V4 neurons were shorter in the luminance-cue condition than in the motion-cue condition. Meanwhile, the timings of initiation of shape selectivity were not different between cue conditions, indicating a difference in processing time. Middle temporal neurons were less shape modulated in the luminance-cue condition than in the motion-cue condition. Temporal properties of neural activities in the lower bank of anterior superior temporal sulcus were similar between cue conditions. These results suggest that an interaction of the ventral cortex with the dorsal cortex is required for shape discrimination with different visual cues.