Center for Perceptual Systems Seminar Series
Mon, September 24, 2012 • 12:00 PM - 1:00 AM • SEA 4.244
"Constructing a stable world from an unstable retinal image: interactions between visual and oculomotor systems"
Elisha Merriam, Ph.D.
Center for Neural Science, Heeger lab
New York University
Monday, September 24
Reception with Refreshments at 11:30 AM
Find information about current and upcoming talks at CPS on our website:http://www.utexas.edu/cola/centers/cps/events/upcoming.php
Abstract: As the eyes move, objects in the world change position on the retina. Despite the constant displacement of retinal images, a coherent and stable visual scene is perceived. This phenomenon, termed spatial constancy, indicates that the brain constructs a stable representation of the visual world by combining information about eye movements with sensory information from the visual system. I will describe a series of fMRI studies in humans that explore how visual information is transformed from an unstable retinal input to a stable and coherent visual percept. I show that all of human visual cortex represents stimulus location in an eye-centered (retinotopic) reference frame, as opposed to a world-centered (spatiotopic) reference frame. I will present neuroimaging evidence that non-retinal eye position signals modulate visual responses in many cortical areas, producing eye position gain fields that resemble classic recordings from monkey parietal cortex. Using multivariate analysis methods, I show that eye position gain fields may be used by the brain to continually reconstruct stimulus location as the eyes move. Finally, I will show that eye movement signals have a profound effect on visual activity, even during the small 'microsaccade' eye movements that occur involuntarily during intended fixation. Together, these studies suggest that visual perception arises from an active process that tightly integrates information from the oculomotor system.