Phonagnosia, a Voice Homologue to Prosopagnosia
56.4036, Tuesday, 19-May, 2:45 pm - 6:45 pm, Pavilion
Irving Biederman1,2, Sarah Herald2, Xiaokun Xu1, Ori Amir1, Bryan Shilowich1; 1Department of Psychology, University of Southern California, 2Neuroscience, University of Southern California
Most cases of prosopagnosia—the inability to recognize faces—are “developmental,” most likely congenital, in contrast to those that are “acquired” through injury or stroke. There has never been a comprehensive account of the neural basis for the developmental form of this deficit (dPros) in which, somewhat paradoxically, such individuals appear to show normal localization of posterior face areas (OFA and FFA) as well as STS (in contrast to acquired prosopagnosia). dPros demonstrate normal discrimination of faces as same or different but cannot can imagine familiar faces. An investigation of a rare condition of developmental phonagnosia (dPhon)—the inability to individuate familiar people on the basis of their voice--has suggested the possibility of a common account of both conditions. In a manner parallel to dPros, dPhons can discriminate unfamiliar voices as same or different but cannot imagine familiar voices, although they have no trouble in imagining non-voice sounds. A region in the ventromedial prefrontal cortex (vmPFC) may function as a person identification node (PIN, Bruce & Young, 1986) in that it is activated by viewing personally familiar faces or imagining familiar voices (Fig. 1) in normal controls but not by unfamiliar faces repetitively viewed during the course of an experiment. Neither deficit is a consequence of a degraded perceptual representation which would have led to an inability to discriminate faces or voices, but a failure to activate a familiar identity based on face or voice. The conditions are also not a consequence of a general deficit in the functioning of vmPFC as a PIN as dPros and dPhons are normal in recognizing familiar voices or faces, respectively. The conditions may arise from a deficiency in the white matter connections to vmPFC from face-selective areas in the posterior part of the brain (for dPros) and prosody-selective areas (for dPhons).