Impaired social cognition in mild Alzheimer disease.

Abnormal decoding of social information has been associated with the conversion from prodromal Alzheimer's disease (AD) to dementia. Since the distributed neural networks involved in face processing are differentially affected in prodromal and dementia states of AD and in Fronto-Temporal Dementia (FTD), we hypothesized a differential impairment in face processing in these populations. Facial expression, gender and gaze direction decoding abilities were examined in patients with probable amnesic Mild Cognitive Impairment (aMCI, N=10) fulfilling criteria for prodromal AD, in patients with mild and moderate AD (N=10) as well as in FTD patients (N=10) and in a group of age- and sex-matched healthy comparison subjects (N=10). Gender recognition was preserved in all groups. Compared to controls, patients with mild or moderate AD were impaired in expression recognition and FTD patients were impaired in expression and gaze direction determination, whereas MCI patients were not impaired at all.