Facial Identity And Facial Speech Processing In Developmental Prosopagnosia

Abstract

Developmental prosopagnosia is the life-long impaired ability to recognize familiar faces. The neural basis of this condition remains a matter of investigation. Face processing networks are bilateral but have right hemisphere dominance, and the location of lesions in acquired prosopagnosia is in keeping with this. There may be a complementary contribution from left hemisphere regions to certain types of face processing, and prior reports suggest that this might involve processing faces depicted by line contours or facial speech patterns by lip reading. We performed two studies in seven subjects with developmental prosopagnosia. The first task tested participants’ ability to match faces across viewpoint changes, with either unaltered photographs or high contrast line-drawing-like images. The second task involved a series of lip-reading tests to examine ability to perceive facial speech patterns. Performance on these two tasks was compared to twenty-three age- and education-matched control subjects. Prosopagnosic subjects had normal performance with line-contour faces, but facial processing showed no improvement with the added information in unaltered photographs. In facial speech pattern tests developmental prosopagnosic subjects could detect, discriminate, and identify facial speech patterns, but compared to controls, there was reduced use of visual cues or anomalous audiovisual integration in the McGurk effect, with only one subject performing normally. We conclude that developmental prosopagnosia may have a broader range of face processing impairment beyond just identity recognition. There can be association with a subtle impairment in lip-reading, which has been associated more with left than right fusiform damage after acquired lesions.