Representations of faces and body parts in macaque temporal cortex: a functional MRI study

Abstract

Human neuroimaging studies suggest that areas in temporal cortex respond preferentially to certain biologically relevant stimulus categories such as faces and bodies. Single-cell studies in monkeys have reported cells in inferior temporal cortex that respond selectively to faces, hands, and bodies but provide little evidence of large clusters of category-specific cells that would form "areas." We probed the category selectivity of macaque temporal cortex for representations of monkey faces and monkey body parts relative to man-made objects using functional MRI in animals trained to fixate. Two face-selective areas were activated bilaterally in the posterior and anterior superior temporal sulcus exhibiting different degrees of category selectivity. The posterior face area was more extensively activated in the right hemisphere than in the left hemisphere. Immediately adjacent to the face areas, regions were activated bilaterally responding preferentially to body parts. Our findings suggest a category-selective organization for faces and body parts in macaque temporal cortex.

Fig. 1.

Category-selective representations of faces and body parts in monkey temporal cortex. (A) Coronal slices of monkeys M1 and M2 depicting voxels activated significantly more by faces compared to objects. (B) Same coronal slices depicting voxels activated significantly more by body parts compared with objects. Approximate locations of the coronal slices (1, 2) are indicated on a sagittal slice. Scale indicates Z-score values of functional activity in colored regions. R, right hemisphere.

Fig. 2.

Topographic relationship of face and body part areas. Inflated and flattened cortical surface representations of the left and right hemispheres of monkeys M1 (A) and M2 (B). Activated voxels are color-coded according to their preferred category. Faces > objects, red; body parts > objects, yellow; overlap of the two, blue. sts, superior temporal sulcus; sf, sylvian fissure; ios, inferior occipital sulcus; ots, occipitotemporal sulcus; ls, lunate sulcus; ips, inferior parietal sulcus; cs, central sulcus; as, arcuate sulcus.

Fig. 3.

Time courses of fMRI signals from category-selective areas. (A) Signals from the pFace, pBody, aBody, and aFace areas averaged across two monkeys (M1 and M2). The duration of the visual stimulation epoch is indicated by the black bar. The pBody area was activated only in M1. Note the y-axis scale change for the time courses in the pFace and the aBody areas. (B) Selectivity of each area to faces (red) and body parts (black) relative to objects, computed with an index (see Methods and Results).