Neurones responsive to faces in the temporal cortex: studies of functional organization, sensitivity to identity and relation to perception.

We have investigated the distribution of cells responsive to faces within the macaque temporal cortex and their sensitivity to different face attributes. We found a functional organization of cells responsive to the sight of different views of the head. Cells of a similar type were grouped together both vertically down through the cortex, and horizontally in patches extending 0.5-2.0 mm across the surface of the cortex. A substantial proportion of cells responsive to faces were found to be sensitive to biologically important characteristics such as identity or expression. Cells were found to be highly selective for particular individuals that were familiar to the monkey with selectivity persisting across a great variety of viewing conditions such as changing face expression, orientation, colour, distance and size. Data suggested that sensitivity to identity arises at the level of specific views of the individual (e.g. full face). Information about different views may then be pooled to allow recognition independent of view. Visual transformations that make it difficult for humans to perceive faces (e.g., contrast reversal, isoluminant colour, coarsely quantized images, rotation or inversion) reduced the magnitude or increased the latency of cells' responses to faces. In this way, cell responses were related to perception and not simply to visual qualities of the image.