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Kevin DeSimone, Keith A. Schneider; Resolving an occluded stimulus on the human cortical surface using pRF estimates. Journal of Vision 2012;12(9):752. doi: 10.1167/12.9.752.
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Introduction. Electrophysiology techniques in macaque parietal cortex (Assad & Maunsell, 1995) and fMRI experiments in human temporal cortex (Yi et al, 2008) have indicated a spatiotemporal continuity of visually evoked responses for moving, occluded stimuli. We sought to temporally and spatially resolve such a stimulus in early visual areas and to characterize the signal in the event of occlusion using pRF estimates (Dumoulin & Wandell, 2008). Our experimental goal was to determine whether we could resolve a moving, occluded stimulus within primary and extrastriate cortex. Methods. Subjects’ brains were scanned with a 3 T MRI scanner and a 32-channel head coil. Standard retinotopic mapping and cortical flattening procedures were performed. The stimulus was a set of small (1°) circular apertures traveling at a constant velocity and that bounce off the boundaries of the display and one another. Results. We were able to track the stimuli across the visual field in retinotopic coordinates among multiple visual areas. In addition, we computed the pRF estimates across visual cortex and used these to determine the response to both occluded and unoccluded moving stimulus across the cortical surface. Conclusions. We have demonstrated that the representations on the human cortical surface of moving stimuli and their interactions with occluders can be resolved at different velocities in multiple visual areas.
Meeting abstract presented at VSS 2012
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