The proposed projects will focus on visually-guided grasping under a variety of conditions designed to recruit separate mechanisms for online motor control and long-term perceptual recognition. This division of labour can be mapped onto two distinct streams that have been identified in primate cortex: the dorsal (occipitoparietal) and ventral (occipitotemporal) pathways, respectively.

We will begin by examining the dissociation between vision for action and vision for perception before extending this research to examine their interaction. The research will focus on the regions involved in the grasping of three-dimensional objects, a task which is particularly interesting for theories of dual visual systems because it involves shape processing but for visuomotor control rather than for perceptual discrimination. Based on previous imaging results, we anticipate that our initial experiments win successfully dissociate dorsal (parietal and premotor) areas involved in planning to grasp a particular shape from ventral (inferotemporal) areas involved in recognizing and remembering that shape. We will then investigate whether the relative contributions of these two distinct systems can be manipulated by changes to the stimuli or the task. Specifically, varying the familiarity of the stimuli or introducing a short delay prior to initiation of the grasp can have dramatic effects on subjects' behavioural performance. These effects are believed to be due to changes the demands placed on the two visual streams which should be reflected in the activation in the underlying neural substrates. We also plan to investigate previously unexplored aspects of grasping with fMRI studies, including single-trial analyses to examine the temporal sequencing of neural regions and neurophysiological examinations of grasping in the monkey.

Our application extends previous recent in two ways. First, we have used data monkey physiology and human neuropsychology to ask new questions about brain function in neurologically-intact humans. Second, our goal is to extend past theories which have emphasized the segregation between visual functions to now examine their integration.