Cognitive modelling of face processing: evidence from Alzheimer patients.

This is a prospective neuropsychological study on face processing in Alzheimer's disease (AD). The aim was to assess the prevalence and the nature of face processing disorders in AD, and at investigating possible inter-test dissociations within the framework of currently used face processing models. A standardized four-test battery of unknown face discrimination and familiar face recognition was given to 30 mildly deteriorated patients with AD. Half of the patients performed below the cut-off in at least one of the tests. Deficits in familiar face recognition tests were more frequently observed than deficits in unknown face discrimination tests. There was no correlation between impairment of face processing and overall cognitive impairment or visual disorders. A multiple single case approach allowed us to elicit statistically warranted double dissociations between tasks assessing unknown face discrimination and tasks assessing familiar face recognition. Moreover, the ability to decide whether or not a stimulus is a face or a non-face has proven to be a non-mandatory step to further process the face stimuli. All together, these findings support the hypothesis that distinct pathways are involved in the processing of unknown and familiar faces, as posited by Bruce and Young [Br. J. Psychol. 77, 305-327, 1986].