Cognitive response profile of the human fusiform face area as determined by MEG

Activation in or near the fusiform gyrus was estimated to faces and control stimuli. Activation peaked at 165 ms and was strongest to digitized photog raphs of human faces, regardless of whether they were presented in color or grayscale, suggesting that face- and color-specific areas are functionally separate. Schematic sketches evoked similar to 30% less activation than di d face photographs. Scrambling the locations of facial features reduced the response by similar to 25% in either hemisphere, suggesting that configura tional versus analytic processing is not lateralized at this latency. Anima l faces evoked similar to 50% less activity, and common objects, animal bod ies or sensory controls evoked similar to 80% less activity than human face s. The (small) responses evoked by meaningless control images were stronger when they included surfaces and shading, suggesting that the fusiform gyru s may use these features in constructing its face-specific response. Putati ve fusiform activation was not significantly related to stimulus repetition , gender or emotional expression. A midline occipital source significantly distinguished between faces and control images as early as 110 ms, but was more sensitive to sensory qualities. This source significantly distinguishe d happy and sad faces from those with neutral expressions. We conclude that the fusiform gyrus may selectively encode faces at 165 ms, transforming se nsory input for further processing.