Projects
The effects of volition on express saccadic eye movements. Work in this lab has shown that the ultra short reaction time movements known as express saccades need not merely be a reflex response to suddenly appearing stimuli, but can be altered by a spatial instruction to the subject. For example, if a subject is instructed to make a saccade to one side of a visual stimulus, regardless of where it appears, the vector displacement of the saccade will be affected without an increase in reaction time.
Guidance of saccades by scene-based spatial memory. In everyday life, accurate, precise saccades can be made to elements of the visual scene that cannot be seen clearly prior to the eye movement, provided that the element has been "visited" by the eyes before. We are interested in the mechanisms of the scene-based spatial memory system that facilitate this behavior.
Saccadic inhibition and the conflict between reflexive and voluntary movement. Movements result from a combination of sensory signals and cognitive commands. We have studied how reflexive and voluntary saccade commands can interfere with each other. Recent work (Edelman and Xu, 2009) has shown that the presentation of a nearby distractor can facilitate a voluntary saccade to a nearby location whereas a distant distractor briefly, but strongly inhibits voluntary saccades.
The dependence of saccade latency on motor training and target location probability Work in the lab has shown that a high yield of ultra-short reaction-time saccades (express saccades) is made after a few sessions of training and that location probability has a smaller effect on the probability of express saccade occurrence. This is consistent with the possibility that express saccades are a common occurrence in everyday life.