Does prosopagnosia take the eyes out from faces? Evidence for a defect in the use of diagnostic facial information in a brain-damaged patient

Abstract

One of the most impressive disorders following brain damage to the ventral occipito-temporal cortex is prosopagnosia, or the inability to recognize faces. Although cases of acquired prosopagnosia with preserved general visual and memory functions are rare, several cases have been described in the neuropsychological literature and investigated neuro-functionally over the last decades. Yet, a fundamental question remains unresolved: which facial information do these patients use (or not) when they process faces? To address this question, we investigated PS, a case of prosopagnosia with normal object recognition and with a functionally preserved right middle fusiform gyrus — the ‘Fusiform Face Area’, FFA — (Rossion et al., 2003) using a response classification technique sampling information in 3D space (2D image × spatial frequencies, Bubbles, Gosselin and Schyns, 2001). Patient PS and control participants determined the identity of 10 neutral and happy faces (5 females). Comparative analysis of information use revealed that PS and controls dramatically differed on learning curve, amount of information used (i.e. number of bubbles) and the features attended to resolve the task. Across faces, PS did not use the eyes (the optimal information) to identify faces but the mouth, in marked contrast to controls. These findings confirm and quantify the idea that prosopagnosic patients rely on sub-optimal information to identify faces, and pave the way to exploit this information for rehabilitation.

Footnotes

 We are sincerely grateful to P.S. for her patience and motivation during the entire study. Roberto Caldara was supported by a post-doctoral fellowship provided by the Swiss National Science Foundation.