Impairment of speech-reading in prosopagnosia

Abstract

The face is a source of information processed by a complex system of partly independent subsystems. The extent of the independence of processing personal identity, facial expression and facial speech remains at present unclear. We investigated the speech-reading ability of a prosopagnosic patient, LH, who is severely impaired on recognition of personal identity and recognition of facial expressions. Previous reports of such cases raised the possibility that speech-reading might still be intact, even if almost all other aspects of face processing are lost. A series of speech-reading tasks were administered to LH including still photographs, video clips, short-term memory tasks for auditory and speech-read materials, and tasks aimed at assessing the impact of the visual input on auditory speech recognition. LH was severely impaired on these tasks. We conclude that in LH there is a strong association between severe face processing deficits and loss of speech-reading skills.