Face processing in Alzheimer's disease - defining the deficit

Impaired face recognition is a frequently reported, highly emotive early symptom in Alzheimer's disease (AD). AD patients become unable to recognise known people, including relative and close friends, causing much distress. Problems with recognising familiar faces have typically been attributed to the hallmark episodic memory deficit in AD and the degradation of consolidated memories. However, a more recent study has suggested impaired face recognition may have a different etiology. Lavallee et al. (2016) asked AD patients to match simultaneously presented unfamiliar faces, presented either upright or reversed. The rational for using inverted faces was based on the face-inversion effect, i.e. impairment in recognising inverted unfamiliar faces. AD patients showed a reduced inversion effect reflecting an impaired ability to build a coherent perceptual representation of individual faces. This suggests that impaired facial processing may not be solely due to the hallmark amnesic syndrome that characterises AD, but may also be due to impaired higher-level visual processing.

The delineation of the underlying mechanism has implications for intervention and management. Firstly, processing of human faces is critical for most social interaction. Social cognition is impaired in AD patients with progression of disease burden, which in turn is linked to poorer outcomes for patients and greater caregiver distress. However, an increasing body of literature suggests that some patients may develop social deficits earlier in the disease process, with links to impaired face processing. Identifying the mechanisms that underpin impaired face recognition in AD could therefore help to identify those patients more likely to develop social deficits.

Secondly, determining the memory vs perceptual processes linked to face recognition will help to devise evidence-based, tailored rehabilitation protocols for AD patients to support social functioning and maintain quality of life for...