Learning of peri-saccadic visual stimuli
56.525, Tuesday, May 14, 2:45 - 6:45 pm, Vista Ballroom
Yuval Porat1, Ehud Zohary1,2,3; 1Neurobiology Department, Alexander Silberman Institute of Life Sciences, Hebrew University of Jerusalem, 2Interdisciplinary Center for Neural Computation, Hebrew University of Jerusalem, 3The Edmond & Lily Safra Center for Brain Sciences, Hebrew University of Jerusalem
Introduction: Humans naturally scan the visual scene by making fast, ballistic eye movements at about three times per sec. These saccades could potentially result in a smeared and jerky image of the world, but visual perception is clearly immune to such effects. One suggestion is that this perceptual constancy is accomplished by saccadic suppression: a sharp drop in visual sensitivity during a saccade. Saccadic suppression has repeatedly been demonstrated, but the neural mechanisms underlying it are less clear (e.g. at what level in the visual pathways does suppression occur). Specifically, it is unknown if saccadic suppression can be gated by higher level mechanisms such as selective attention. Methods: Subjects performed a visual discrimination task while their eye movements were being recorded. Using a gaze-contingent paradigm, a visual stimulus (elliptic contour) was briefly presented during the execution of a horizontal saccade. In each trial, upon saccade completion, subjects reported the orientation of the ellipse (horizontal vs. vertical). Specificity to the location of the stimulus and the direction of the saccade were assessed by testing the degree of learning transfer to novel untrained conditions. Results: Performance was measured by the slope of the psychometric function (the percent of vertical choices as a function of the ellipse axes aspect-ratio). Preliminary results suggest that subjects improve considerably in this peri-saccadic discrimination task. Improvement was generalized over different saccade directions but not over different stimuli locations. Conclusion: Perceptual learning is possible even when stimuli are presented only during a saccade. Thus, peri-saccadic visual information can be processed at will. This suggests that at least some of the behavioral suppression is caused by high-level cortical mechanisms. References: Volkmann, F. C. (1962). Vision during voluntary saccadic eye movements. Journal of Optical Society of America, 52, 571578.