Attention to form or surface properties modulates different regions of human occipitotemporal cortex.

We carried out 2 functional magnetic resonance imaging experiments to investigate the cortical mechanisms underlying the contribution of form and surface properties to object recognition. In experiment 1, participants performed same-different judgments in separate blocks of trials on pairs of unfamiliar "nonsense" objects on the basis of their form, surface properties (i.e., both color and texture), or orientation. Attention to form activated the lateral occipital (LO) area, whereas attention to surface properties activated the collateral sulcus (CoS) and the inferior occipital gyrus (IOG). In experiment 2, participants were required to make same-different judgments on the basis of texture, color, or form. Again attention to form activated area LO, whereas attention to texture activated regions in the IOG and the CoS, as well as regions in the lingual sulcus and the inferior temporal sulcus. Within these last 4 regions, activation associated with texture was higher than activation associated with color. No color-specific cortical areas were identified in these regions, although parts of V1 and the cuneus yielded higher activation for color as opposed to texture. These results suggest that there are separate form and surface-property pathways in extrastriate cortex. The extraction of information about an object's color seems to occur relatively early in visual analysis as compared with the extraction of surface texture, perhaps because the latter requires more complex computations.