Visuo-motor transformations for arm reaching.

Visuomanual co-ordination requires the merging of ocular and arm information in a common frame of reference. Here we consider behavioural evidence in humans for the use of a viewer-centred frame in the specification of end point positions of reaching. We then review anatomical and neurophysiological data in the non-human primate that indicate a prominent role of the parietal cortex in the process of multisensory fusion that leads to egocentric representations of space. Finally, we discuss the functional anatomy of the human parietal cortex in visuomanual co-ordination as revealed by neuroimaging.