title: Color signals in human motion-selective cortex.
abstract: The neural basis for the effects of color and contrast on perceived speed was examined using functional magnetic resonance imaging (fMRI). Responses to S cone (blue-yellow) and L + M cone (luminance) patterns were measured in area V1 and in the motion area MT+. The MT+ responses were quantitatively similar to perceptual speed judgments of color patterns but not to color detection measures. We also measured cortical motion responses in individuals lacking L and M cone function (S cone monochromats). The S cone monochromats have clear motion-responsive regions in the conventional MT+ position, and their contrast-response functions there have twice the responsivity of S cone contrast-response functions in normal controls. But, their responsivity is far lower than the normals' responsivity to luminance contrast. Thus, the powerful magnocellular input to MT+ is either weak or silent during photopic vision in S cone monochromats.
authors.affiliation: Department of Psychology, Stanford University, California 94305, USA. wandell@stanford.edu
authors.forename: B A
authors.initials: BA
authors.lastname: Wandell
authors.forename: A B
authors.initials: AB
authors.lastname: Poirson
authors.forename: W T
authors.initials: WT
authors.lastname: Newsome
authors.forename: H A
authors.initials: HA
authors.lastname: Baseler
authors.forename: G M
authors.initials: GM
authors.lastname: Boynton
authors.forename: A
authors.initials: A
authors.lastname: Huk
authors.forename: S
authors.initials: S
authors.lastname: Gandhi
authors.forename: L T
authors.initials: LT
authors.lastname: Sharpe
mesh_terms: D000221:Adaptation, Ocular / Q000502:physiology; D000293:Adolescent; D000328:Adult; D003116:Color; D003118:Color Perception / Q000502:physiology*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D009039:Motion Perception / Q000502:physiology*; D009473:Neuronal Plasticity / Q000502:physiology; D010775:Photic Stimulation; D017949:Retinal Cone Photoreceptor Cells / Q000502:physiology; D014793:Visual Cortex / Q000033:anatomy & histology / Q000502:physiology*