Martin Paré

Departments of Physiology and Psychology

Queen's University

Kingston, ON

Neural mechanisms regulating the selection of visual objects for eye movements.

Active vision entails alternating periods of saccadic eye movements and fixations, during which perceptual processing can take place. This natural visual behavior has been best studied with the visual search paradigm-the search of a target among distractors- which have suggested that two distinct processing stages precede saccade initiation: an initial scene analysis that direct visual attention to the target and the subsequent planning of the saccade. This talk will describe how these processes are reflected in the activity of sensory-motor neurons within the parietal cortex and the superior colliculus when animals are performing a rather unconstrained visual search task that mimics natural visual behavior. I will first show that the activity of sensory-motor neurons predicts simultaneously the goal and latency of search saccades, suggesting that visual attention is shifted concomitantly with saccade planning during natural visual behavior. Second, I will present evidence that this selective neuronal activity also reflects the identity of a visual stimulus presented in a neuron's receptive field, possibly accounting for the flexible allocation of attention that enhances the processing of certain visual feature when subjects search heterogeneous displays. Altogether, these findings indicate that saccade target selection arises from the multi-faceted activity of sensory-motor neurons.