fMRI Activation in the Human Frontal Eye Field Is Correlated With Saccadic Reaction Time

1 Canadian Institutes of Health Research Group on Action and Perception, Department of Psychology, University of Western Ontario, London, Ontario; and 2 Centre for Neuroscience Studies, Department of Physiology, Queen's University, Kingston, Ontario, Canada Submitted 13 August 2004; accepted in final form 5 December 2004 Variation in response latency to identical sensory stimuli has been attributed to variation in neural activity mediating preparatory set. Here we report evidence for a relationship between saccadic reaction time (SRT) and set-related brain activity measured with event-related functional magnetic resonance imaging. We measured hemodynamic activation time-courses during a preparatory "gap" period, during which no visual stimulus was present and no saccades were made. The subjects merely anticipated appearance of the target. Saccade direction and latency were recorded during scanning, and trials were sorted according to SRT. Both the frontal (FEF) and supplementary eye fields showed pretarget preparatory activity, but only in the FEF was this activity correlated with SRT. Activation in the intraparietal sulcus did not show any preparatory activity. These data provide evidence that the human FEF plays a central role in saccade initiation; pretarget activity in this region predicts both the type of eye movement (whether the subject will look toward or away from the target) and when a future saccade will occur. Present address and address for reprint requests and other correspondence: J. D. Connolly, Beckmann Behavioral Biology Bldg., Rm. 333, Div. of Biology, California Institute of Technology, Pasadena, CA 91125 (E-mail: connolly{at}vis.caltech.edu )