The role of the fusiform gyrus in successful encoding of face stimuli

PET was used to measure regional cerebral blood flow (rCBF) while memorizin g pictures of unfamiliar human faces presented one at a time (FaceMemory). Other conditions included: (1) FaceRepeat-memorization of four individual f aces presented repeatedly; (2) FaceWatching-viewing passively single faces without overt memory demands; and (3) Scrambled-counting dots superimposed on pictures of scrambled faces. After each FaceMemory condition and after t he final FaceWatching condition scan, recall was tested by measuring face r ecognition. Contrasting FaceMemory and Scrambled conditions revealed severa l temporal activations: right midfusiform and bilateral anterior fusiform g yri. Contrasting FaceWatching and Scrambled conditions showed bilateral act ivation in the temporal poles and in the anterior fusiform gyri, No hippoca mpal activation arose from any contrast. Region of interest analyses on the above areas showed correlations with performance: (1) only rCBF in the rig ht midfusiform correlated positively with encoding during the FaceMemory an d FaceWatching conditions; (2) in the right temporal polar cortex rCBF decr eased during FaceMemory and correlated positively with performance, whereas rCBF increased during FaceWatching and correlated negatively with incident al performance; and (3) activity in the anterior fusiform gyri remained con stant across the conditions of FaceMemory, FaceRepeat, FaceWatching, and Sc rambled and was uncorrelated with performance. These data suggest an expand ed mnemonic role for the right midfusiform in depth of processing/encoding efface information, temporal polar cortex in face perception and recognitio n, and anterior fusiform activity in featural visual feature processing.