Figure 1.

FMRI of alert fixating macaque reveals hot-spots, or “globs”, of color-preferring brain activity in posterior inferior temporal cortex, the brain region anterior to V3, consisting of V4, PITd, and posterior TEO. Visual area boundaries were determined using responses to checkerboard stimuli restricted to wedges along the vertical and horizontal meridians (Supplementary Figure 1). Top, a computationally flattened map, the average of all data for this monkey; sulci are indicated by dark grey. Middle, coronal sections showing responses from two independent data sets (40 stimulus runs each; approximate anterior-posterior position indicated at right). Color-preferring regions were identified as those that responded more strongly to equiluminant colored stripes than to achromatic stripes. Labels 1-7 identify prominent globs, and facilitate a comparison between the raw slice data and the computationally manipulated flattened data. Significance depicted by color bar. LGN, lateral geniculate nucleus; s.t.s., superior-temporal sulcus; o.t.s., occipital-temporal sulcus; i.o.s., inferior-occipital sulcus; l.s., lunate sulcus.

Bottom, traces show the time course of the fMRI response to achromatic stripes (grey columns); red/blue colored stripes of various red-to-blue luminance ratios (pink columns); and responses to uniform grey (white columns). Area MT shows stronger responses to achromatic stripes than to any colored stripes, and shows a minimum to colored stripes that are approximately equiluminant (color ratios 0 and 0.33). The globs show stronger responses to all colored stripes; and the inter-globs show similar magnitude responses to color and achromatic stripes. Responses were measured using a contrast agent, which results in a negative fMRI signal (traces have been flipped vertically, and de-trended). Scale bar = 1cm.