Attentional modulation of fMRI responses in human V1 is consistent with distinct spatial maps for chromatically defined orientation and contrast.

Attending to different stimulus features such as contrast or orientation can change the pattern of neural responses in human V1 measured with fMRI. We show that these pattern changes are much more distinct for colored stimuli than for achromatic stimuli. This is evidence for a classic model of V1 functional architecture in which chromatic contrast and orientation are coded in spatially distinct neural domains, while achromatic contrast and orientation are not.