Abstract
Inversion disrupts face recognition more than object recognition, and neuropsychological patients have shown behavioral dissociations between upright and inverted faces. These effects suggest that upright and inverted faces engage different mechanisms, but the neural basis for this difference is not clearly understood. Here we used repetitive transcranial magnetic stimulation (rTMS) to examine the role of a core component in the face-processing network, the occipital face area (OFA), in the perception of upright and inverted faces. A previous study demonstrated that rTMS to the right OFA disrupted perception of upright face parts (Pitcher, Walsh, Yovel & Duchaine, 2007). Here we tested inverted face stimuli that varied in either the face parts (eyes and mouth) or the spacing between these parts (Yovel & Kanwisher, 2004). Subjects performed a sequential same / different discrimination task while rTMS (10Hz for 500ms) was targeted at the right OFA, the left OFA, or vertex (a TMS control site). Discrimination of the inverted face part stimuli was impaired when rTMS was targeted at the right OFA only. rTMS had no effect on the inverted face spacing stimuli and had no significant effect on either type of face stimuli at the left OFA. In combination with our earlier-published results for upright face stimuli, these findings indicate that the right OFA represents face components regardless of face orientation. In a second experiment we examined the role of the lateral occipital (LO) object region in the processing of inverted and upright faces. Preliminary results suggest that whereas rTMS to the rOFA impaired perception of both upright and inverted faces, rTMS to rLO impaired discrimination of only inverted faces. Taken together, these results suggest that inverted faces are processed both by the occipital face-specific mechanisms (OFA) and more general object-selective mechanisms (LO), whereas upright faces are primarily processed by face-selective regions.