Covert processing of faces in prosopagnosia is restricted to facial expressions: evidence from cross-modal bias.

We present a single case study of a brain-damaged patient, AD, suffering from visual face and object agnosia, with impaired visual perception and preserved mental imagery. She is severely impaired in all aspects of overt recognition of faces as well as in covert recognition of familiar faces. She shows a complete loss of processing facial expressions in recognition as well as in matching tasks. Nevertheless, when presented with a task where face and voice expressions were presented concurrently, there was a clear impact of face expressions on her ratings of the voice. The cross-modal paradigm used here and validated previously with normal subjects (de Gelder & Vroomen, 1995, 2000), appears as a useful tool in investigating spared covert face processing in a neuropsychological perspective, especially with prosopagnosic patients. These findings are discussed against the background of different models of the covert recognition of face expressions.