Congenital prosopagnosia: face-blind from birth.

Congenital prosopagnosia: face-blind from birth

Congenital prosopagnosia refers to the deficit in face processing that is apparent from early childhood in the absence of any underlying neurological basis and in the presence of intact sensory and intellectual function. Several such cases have been described recently and elucidating the mechanisms giving rise to this impairment should aid our understanding of the psychological and neural mechanisms mediating face processing.

Aside from the intrinsic interest in the study of neurodevelopmental disorders, CP has the potential to inform our understanding of the psychological and neural mechanisms underlying face processing and their relationship to non-face processing. For example, the fact that CP exists at all and that, over the course of their lifetime the deficit is not resolved in these individuals, suggests that there is a limit on the plasticity of the human ventral visual system; this is in marked contrast with the rather widespread plasticity reported in other sensory domains as well as in higher-cognitive skills such as language. Studying CP individuals also enables us to examine the neural mechanisms mediating face recognition using fMRI or other imaging techniques, unaffected by damage that might disrupt normal blood flow or neurovascularization in cases of AP. Hence the fact that the CP individuals show normal BOLD activation of the fusiform face area and other ventral cortical structures is highly provocative and challenges us to generate a more refined and precise notion of the computational properties of these occipito-temporal areas. We should also note that CP might not be as rare as previously thought and, like other developmental disorders, questions about intervention and training will become more pressing.

Finally, many of the individuals with CP tested so far, both in our studies and in the literature, have a family member who is also impaired at face processing. This familial component is of great interest and studies of the genetic predisposition and mechanism will allow us to start building bridges between behavior and cortical development. The only genetic investigations of which we are aware to date reports that the cumulation segregation ratios are compatible with a simple autosomal dominant mode of inheritance but the molecular DNA and linkage studies have not been reported. Despite the recent progress in the characterization of CP, many outstanding questions exist and a full explanation of the psychological and neural mechanisms giving rise to CP remains elusive.