Lip-reading abilities in a subject with congenital prosopagnosia.

We present the case of an individual with congenital prosopagnosia or "face blindness", a disorder where the ability to recognize faces is impaired. We studied the lip-reading ability and audiovisual perception of this subject using a DVD with four conditions (audiovisual congruent, auditory, visual, and audiovisual incongruent) and compared results with a normal patient cohort. The patient had no correct responses in the visual lip-reading task; whereas, he improved in the audiovisual congruent task. In the audiovisual incongruent task, the patient provided one response; thus, he was able to lip-read. (He was able to use lip-reading/to use labial informations) This patient perceived only global dynamic facial movements, not the fine ones. He had a sufficient complementary use of lip-reading in audiovisual tasks, but not visual ones. These data are consistent with abnormal development of the pathways used for visual speech perception and associated with second-order face processing disorders and normal development of the audiovisual network for speech perception.