Stimulus-selective properties of inferior temporal neurons in the macaque.

Previous studies have reported that some neurons in the inferior temporal (IT) cortex respond selectively to highly specific complex objects. In the present study, we conducted the first systematic survey of the responses of IT neurons to both simple stimuli, such as edges and bars, and highly complex stimuli, such as models of flowers, snakes, hands, and faces. If a neuron responded to any of these stimuli, we attempted to isolate the critical stimulus features underlying the response. We found that many of the responsive neurons responded well to virtually every stimulus tested. The remaining, stimulus-selective cells were often selective along the dimensions of shape, color, or texture of a stimulus, and this selectivity was maintained throughout a large receptive field. Although most IT neurons do not appear to be "detectors" for complex objects, we did find a separate population of cells that responded selectively to faces. The responses of these cells were dependent on the configuration of specific face features, and their selectivity was maintained over changes in stimulus size and position. A particularly high incidence of such cells was found deep in the superior temporal sulcus. These results indicate that there may be specialized mechanisms for the analysis of faces in IT cortex.