Effect of Stimulus Size on the Dynamics of Orientation Selectivity in Macaque V1

• Published in: Journal of neurophysiology 2005-07, Vol.94 (1), p.799-812
• Main Authors: Xing, Dajun, Shapley, Robert M, Hawken, Michael J, Ringach, Dario L
• Format: Article
• Language: English
• Subjects: Animals; Macaca fascicularis; Models, Neurological; Neural Inhibition; Nonlinear Dynamics; Orientation - physiology; Pattern Recognition, Visual - physiology; Photic Stimulation - methods; Space Perception - physiology; Time Factors; Visual Cortex - physiology
• ISSN: 0022-3077; 1522-1598
• DOI: 10.1152/jn.01139.2004

1 Center for Neural Science, New York University, New York, New York; and 2 Departments of Neurobiology, Psychology, and Brain Research Institute, University of California, Los Angeles, California Submitted 5 November 2004; accepted in final form 15 February 2005 Previous research has established that orientation selectivity depends to a great extent on suppressive mechanisms in the visual cortex. In this study, we investigated the spatial organization and the time-course of these mechanisms. Stimuli were presented in circular windows of "optimal" and "large" radii. The two stimulus sizes were chosen based on an area-response function measured with drifting gratings at high contrast. The "optimal" size was defined as the smallest radius that elicited the peak response (average value of 0.45°), whereas "large" was defined as two to five times the optimal size. We found that the peak amplitude of tuned enhancement and untuned suppression varied