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Junjie Liu, Alyssa A. Brewer, Brian A. Wandell; Variations in temporal and chromatic responses across human visual cortex. Journal of Vision 2004;4(8):318. doi: 10.1167/4.8.318.
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© ARVO (1962-2015); The Authors (2016-present)
BACKGROUND. Regions within human visual cortex have different computational specializations. We are exploring the temporal and chromatic responses across visual cortex to learn more about the specializations for color. METHODS. Retinotopic maps were measured in three human subjects using small (3 deg radius) expanding ring and rotating wedge stimuli. Cortical regions representing 1–2.5 degree eccentricity were identified in V1/2/3, V3A, ventral occipital cortex (VO) and MT+. In each region fMRI contrast response functions to S-, (L−M)- and (L+M)-cone flickering patterns (3 deg radius, radial gratings, 0.8 cycle/degree) were measured at 1.5 and 7.5Hz frequencies. Subjects performed an attention control task during the measurements. RESULTS. MT+ and V3A are more sensitive to 7.5 than 1.5Hz for all color stimuli. Conversely, VO is more sensitive to 1.5 than 7.5Hz for all color stimuli. In MT+ and V3A, 1.5Hz responses to both L−M and S-cone modulations are quite low; 7.5Hz responses to S-cone modulations are slightly higher, but 7.5Hz responses to L−M modulations are significantly higher and comparable to the 7.5Hz L+M responses. In VO, 1.5Hz responses to S-, (L−M)- and (L+M)-cone modulations are all strong and comparable to each other; 7.5Hz responses to all modulations are weaker but still comparable to each other. CONCLUSIONS. Similar to human motion perception, MT+ and V3A respond well to only some color dimensions, and more powerfully to high than to low temporal frequencies. Similar to human color judgments, VO responds well to all color dimensions, and more powerfully to low than to high temporal frequencies.
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