Abstract
We performed two monkey fMRI experiments to identify cortical regions involved in face configuration processing. In experiment 1, real and schematic faces (replaced face features with gray ovals) with veridical and scrambled configurations were created by manipulating face configurations and features orthogonally. Mosaic-scrambled versions of all faces were used to control for low-level differences across conditions. In experiment 2, veridical and scrambled faces were created by disassembling a composite image (four veridical faces positioned around a fixation point) in two ways. We either presented each full set of face features from one of the four veridical faces separately, or spread them over the four faces (hence showing four different features from the four different faces). This resulted in scrambled faces that fully controls for local low-level stimulus differences compared to the veridical faces while destroying the veridical configurations. To further control for different degrees of stimulus spreading and asymmetry, we created two other conditions with face features arranged in a scrambled configuration at each of the four positions in the initial composite images. Finally, two additional control conditions were created with objects. Three monkeys were scanned (3T, contrast-enhanced, 1.25 mm isotropic) while performing a fixation task. Results of both experiments revealed a significant face configuration effect in four face patches: bilateral ML and MF, left AD and a prefrontal patch rPLf. Although a significant 3-way interaction (configuration x face type x mosaic-scrambling) was found in MF, lAD and rPLf, only lAD and rPLf showed a face configuration effect with the real, but not schematic faces (Exp. 1). Furthermore, only ML and MF, but not lAD and rPLf showed a significant face feature effect (Exp. 2). These suggest a unique role of lAD and rPLf in processing intact veridical face configurations, but not schematic face-like configurations and face features in monkeys.
Meeting abstract presented at VSS 2014