Abstract
Although faces are naturally seen in both left/right and up/down rotated views, virtually all fMRI work on the representation of face views has examined only left/right rotation around frontal views. Accordingly, we designed an fMRI adaptation study to test multiple cortical areas for up/down viewpoint selectivity. Face-selective regions of interest were determined in a block-designed scan comparing responses to faces versus houses. This identified five face-selective regions of interest: fusiform face area (FFA), occipital face area (OFA), lateral occipital complex (LOC), superior temporal sulcus (STS), and inferior frontal sulcus (IFS). Event-related scans with a cross-adaptation paradigm were used to examine BOLD signals in each face region. Subjects adapted to frontal, up 20°, or down 20° views followed by one of these as a test view, thus producing nine different adapt/test combinations. Twelve subjects with normal vision were scanned. An initial two way ANOVA examined effects of hemisphere and self-adaptation (i.e. identical test and adapt stimuli). This analysis showed an effect of hemisphere (right magnitudes larger) only in FFA, and significant adaptation effects in FFA (p <0.001), OFA (p <0.01), and IFS (p <0.028). A second ANOVA compared results for all adapt and test view combinations to their no adapt conditions in these three areas. FFA and IFS showed a significant cross-adaptation as well as self-adaptation. In general, upward faces produced greater adaptation than adaptation to frontal or downward faces in these areas, thus indicating view selective tuning in the up/down direction. Results in OFA, however, suggest an invariance to up/down head rotation. Thus, up/down head rotation is encoded in some but not all face selective cortical areas.