Face percept formation in human ventral temporal cortex

Loci in ventral temporal cortex are selectively active while viewing faces and other objects, but it remains unclear whether these areas represent accumulation of simple visual information, or processing of intact percept. We measured broadband electrocorticographic changes from implanted electrodes on the ventral temporal brain surface while showing patients noise-degraded images of faces and houses. In a subset of posterior fusiform gyrus face-selective regions, cortical activity decreased parametrically with noise increase, until the perceptual threshold. At noise levels higher than the perceptual threshold, and for house stimuli, activity remained at baseline. We propose that this convergence of proportional and thresholded response may identify active areas where face percepts are extracted from simple visual features. These loci exist within a topological structure of face percept formation in the human ventral visual stream, preceded by category non-selective activity in peri-calcarine early visual areas, and in concert with all-or-nothing activity in post-perceptual sub-regions of the ventral temporal lobe. This topological organization suggests a physiological basis for the anatomy of face perception, explaining different perceptual deficits following temporal lobe injury.

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