Responses to lightness variations in early human visual cortex |
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Authors: | Boyaci Huseyin Fang Fang Murray Scott O Kersten Daniel |
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Institution: | Department of Psychology, University of Minnesota, Minneapolis, Minnesota 55455, USA. boyac003@umn.edu |
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Abstract: | Lightness is the apparent reflectance of a surface, and it depends not only on the actual luminance of the surface but also on the context in which the surface is viewed 1-10]. The cortical mechanisms of lightness processing are largely unknown, and the role of early cortical areas is still a matter of debate 11-17]. We studied the cortical responses to lightness variations in early stages of the human visual system with functional magnetic resonance imaging (fMRI) while observers were performing a demanding fixation task. The set of dynamically presented visual stimuli included the rectangular version of the classic Craik-O'Brien stimulus 3, 18, 19] and a variant that led to a weaker lightness effect, as well as a pattern with actual luminance variations. We found that the cortical activity in retinotopic areas, including the primary visual cortex (V1), is correlated with context-dependent lightness variations. |
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