Wei Wang

Institute of Neuroscience
Chinese Academy of Sciences
w.wang@ion.ac.cn

Abstract

A central question in the visual processing of form and motion is how the cortex integrates local visual cues to form global representations. We investigated the cortical representation of second-order contours defined by contrast modulation, phase reversal, and motion in macaque V1 and V2. We found that the iso-orientation domains elicited by contours defined by contrast modulation or phase reversal were in precise register with those activated by luminance-defined contours. However, iso-orientation domains activated by motion-defined contours were closely correlated with the motion axes of their local-noise inducers rather than the oriented motion contours. A simple spatio-temporal energy model reproduced all our experimental results in V1 and V2. Thus, our simulation and experimental results revealed that population responses to second-order contours in macaque V1 and V2 were driven through the linear processing of local luminance or motion cues within these classical second-order contour stimuli. The central issue addressed here is concerning the cortical loci and integration from local cues into global representations across different hierarchically organized processing stages in primate ventral visual pathway. The population responses recorded in macaque V1 and V2 reflect actually the local luminance or motion cues (physically present) and not the illusory and second-order contours they define (but we see perceptually). Furthermore, our results suggest that the global contours could be accomplished in high-tier visual areas such as in V4 via pooling inputs from multiple V1 and V2 neurons with small spatio-temporal receptive fields that are spatially aligned in precise retinotopic coordinates.

Short Bio

Dr. Wei Wang is a Principal Investigator and Head of the Laboratory of Visual Perceptual Mechanisms. He graduated and received his Ph.D. from University of Science & Technology of China in 1998. He was working as a research fellow and senior research fellow at University College London (UCL), University of Manchester Institute of Science & Technology (UMIST) and University of Manchester (UM) respectively from 1998 to 2006. Dr. Wang was awarded the prestige Wellcome Trust Career Development Research Fellowship at the Faculty of Life Sciences, University of Manchester on 1st June 2006. His major research interests lie in the cortical neural mechanisms of visual perceptual phenomena.