Abstract
Viewing an image sequence of faces of two different people results in a greater BOLD response in the fusiform face area (FFA) compared to when the sequence is composed of identical images of the same person. However, changes in identity necessarily involve changes in the image. Is the release from adaptation a result of a change in face identity per se, or could it be an effect that would be produced by any image change? In a fast event-related fMRI-adaptation (fMR-a) design, subjects viewed a sequence of two faces that could be of the same or different person, and in the same or different orientation (frontal or ∼20° rotated in depth). Critically, the physical similarity of view changes of the same person was scaled, by Gabor-jet differences, to be equivalent to the image change produced by an identity change. Subjects judged, by button press, whether the pair of faces on each trial were the same or different in image size (both in square of 128 or 256 pixels, or one image at each size), a task that allowed them to ignore both person and orientation. Both person and orientation changes produced equivalent releases from adaptation in FFA (relative to images of the same person in the same orientation) suggesting that FFA is sensitive to physical similarity rather than to the individuals depicted in the images.
Funded by NSF BCS 04-20794, 05-31177, 06-17699 to Ivring Biederman.