People with Alzheimer's disease develop problems in recognizing familiar faces. It has been thought that this is just part of their general impairment, but a new study indicates that a specific, face-related impairment develops early in the disease. This impairment has to do with the recognition of a face as a whole.
Face recognition has two aspects to it: holistic (seeing the face as a whole) and featural (processing individual features of the face). While both are useful in object recognition, expert recognition (and face recognition is usually something humans are expert in) is built on a shift from featural to holistic processing.
The study compared the ability of people with mild Alzheimer's and healthy age- and education-matched seniors to recognize faces and cars in photos that were either upright or upside down. It found that those with Alzheimer's performed comparably to the control group in processing the upside-down faces and cars. This type of processing requires an analysis of the various features. Those with Alzheimer’s also performed normally in recognizing upright cars (car experts are likely to use holistic processing, but those with less expertise will depend more on featural processing). However, they were much slower and less accurate in recognizing faces.
Realizing that impaired facial recognition is based on a holistic perception problem, rather than being simply another failure of memory, suggests that strategies such as focusing on particular facial features or on voice recognition may help patients recognize their loved ones for longer.
 . A Qualitative Impairment in Face Perception in Alzheimer’s Disease: Evidence from a Reduced Face Inversion Effect. Journal of Alzheimer's Disease [Internet]. 2016 ;51(4):1225 - 1236. Available from: http://content.iospress.com/articles/journal-of-alzheimers-disease/jad151027