Abstract
Human perception must deal in many cases with dynamism. In face processing dynamism conveys rich social information including facial expression, eye gaze and mouth movements. To examine the response to dynamism within the neural face-processing system, we first identified several face-selective regions using a dynamic face localizer. In addition to the “core” face network, which includes the OFA, FFA and pSTS-FA, the dynamic localizer revealed two additional face areas – the anterior Superior Temporal Sulcus (aSTS-FA) and the Inferior Frontal Gyrus (IFG-FA). A few recent electrophysiology studies in monkeys and neuroimaging studies in humans have shown that areas in the STS and IFG are responsive to voices suggesting a common mechanism for the processing of dynamic visual and auditory information from faces. To assess this predication, we presented subjects with dynamic stimuli of mute faces and audio clips of human speech. Our results show no significant response to human speech in the OFA and FFA while the pSTS-FA, aSTS-FA and IFG-FA showed a significant response to human speech. To further assess whether these areas are selective to human voices we examined their response to human vs. non-human auditory stimuli. The pSTS-FA, aSTS-FA and IFG-FA showed a significantly higher response to human auditory stimuli. In conclusion, our data suggest a clear distinction between two face-selective pathways - the ventral face-selective network including the OFA and FFA, encoding uni-modal, static form information and the dorsal network including the pSTS-FA, aSTS-FA and IFG-FA, encoding dynamic multi-modal information. These findings are inconsistent with the prevalent neural model that defines the pSTS-FA as part of the core face system and instead suggest a clear functional distinction between the pSTS-FA, which is part of a separate network that additionally encodes vocal information, and the OFA and FFA, which represent the visual aspects of a face.
Meeting abstract presented at VSS 2015