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Suzanne McKee, Alex Wade, Mark Pettet, Vladimir Vildavski, Greg Appelbaum, Tony Norcia; Disparity processing in the human brain imaged with high density EEG. Journal of Vision 2007;7(15):84. doi: 10.1167/7.15.84.
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© ARVO (1962-2015); The Authors (2016-present)
Psychophysical thresholds for relative disparity are far better when test and reference targets are presented in the same plane than when targets are presented in two planes separated by a pedestal disparity. Is this sensitivity difference reflected in the aggregate neural responses of different visual areas? We used high-density EEG recording, combined with fMRI-defined regions of interest, to localize the responses to disparity modulation in four visual areas: V1, V3A, V4 and hMT+. The stimulus consisted of randomly-spaced vertical lines. Alternating horizontal strips of the line pattern were either static or modulated repetitively by a 6 arcmin change in disparity. We compared the responses to disparity modulation in the same plane to modulation when the static and modulated strips were separated by a fixed 6 arcmin disparity pedestal. All four areas gave larger responses to modulation in the same plane than to modulation with the 6 arcmin pedestal. However, the biggest difference was observed in area hMT+, not V1. Extra-striate areas do not simply mirror response amplitudes in V1. Indeed, the form of the temporal responses in extra-striate areas was markedly different from the V1 response, suggesting that extra-striate areas may encode disparity-generated surface organization, as well as disparity magnitude.
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