Selectivity of macaque ventral intraparietal area (area VIP) for smooth pursuit eye movements

In the posterior parietal cortex (PPC) of the macaque, spatial and motion signals arising from different sensory signals converge. One of the functional subregions within the PPC, the ventral intraparietal area (VIP), is thought to play an important role for the multisensory encoding of self and object motion. In the present study we analysed the activity of area VIP neurons related to smooth pursuit eye movements (SPEMs). Fifty-three per cent of the neurons (123/234) were selective for the direction of the SPEMs. As evident from control experiments, activity observed during smooth eye movements was more closely related to extraretinal signals than visual parameters. In addition, we examined the sensitivity of area VIP neurons for the velocity of SPEMs. Seventy-four per cent of the pursuit-related neurons had a significant velocity tuning. There was a clear preference for high velocities. Eighty-six per cent of the neurons preferred the highest pursuit velocity (40 deg s(-1)) employed in our study. In everyday life, high pursuit velocities most frequently occur if the pursuit target is located in near-extrapersonal space, i.e. the action space of the head. Together with previous findings, the current results thus suggest that the information provided by VIP neurons may be used to encode motion in near-extrapersonal space and to guide and coordinate smooth eye and head movements within this very part of space.