Structure of the Human Cortical Depth Map

Smith-Kettlewell Eye Research Institute, San Francisco CA

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Abstract

DESCRIPTION (From the Applicant's Abstract): One of the most significant roles of the visual brain is to provide the capability of encoding spatial relations in the three-dimensional world in which we operate. From domestic activities like cooking, to extreme sports and performance skills, an adequate representation of visual (and other sensory) space is an essential prerequisites. Any defects in the representation are likely to cause significant performance deficits and impairment of the quality of life. We therefore propose a combined psychophysical and functional MRI (magnetic resonance imaging) approach to determine the structure of the depth representation in the human brain. The final depth representation is a cortical process that encodes the 3D structure of a scene from all available cues, integrating these specific depth cues in to a unitary depth impression, or 'depth map'. This generic depth map receives input from a range of depth cues, such as binocular disparity, motion parallax, and a host of static monocular depth cues including perspective, shading texture, blur, and contrast. A series of fMRI studies is designed to isolate the cortical processing for each individual depth cue and determine how it feeds in to the generic depth map, with the depth cues psychophysically adjusted for equal salience. Is the depth from each cue processed in a cortical representation of space that is separate for each depth cue? In there only one cortical region concerned with the representation of depth from all cues? Or is there a combination of individual and generic representations? The answers determine the degree of susceptibility of depth representation to degradation by cortical insults. The mapping results will be validated by functional studies of the susceptibility of each cortical area to depth variations and of the time course depth adaptation, and also for insensitivity to contrast variations.