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A recent study has demonstrated that, besides triggering memory lapses, Alzheimer's disease also impairs visual face perception. Research conducted by the team of Dr. Sven Joubert, PhD, a researcher at the Centre de recherche de l'Institut universitaire de geriatrie de Montreal and a Professor with the Department of Psychology at Universite de Montreal, was published today in the Journal of Alzheimer's Disease.

Scientists know that face perception plays a primary role in human communication, and is why humans have become experts at quickly detecting and identifying faces. This ability is thought to depend on the capacity to perceive the entire face. Also known as holistic perception, this ability differs with the local and detailed analysis required to recognize individual facial features, such as the eyes, nose or mouth. Dr. Joubert's study verified that Alzheimer's disease impairs the holistic ability to perceive faces.

The Montreal team recruited people with Alzheimer's along with healthy seniors to examine their capability at perceiving faces and cars in photos that were either upright or upside down. Dr. Joubert explains the team's findings: The results for people with Alzheimer's were similar to those in the control group in terms of answer accuracy and the time to process the upside-down faces and cars. To perform these tasks, the brain must perform a local analysis of the various image components perceived by the eye. However, with the upright faces, people with Alzheimer's were much slower and made more mistakes than the healthy individuals. This leads us to believe that holistic face recognition in particular becomes impaired. Subjects with Alzheimer's disease also demonstrated normal recognition of the upright cars, a task that in theory does not require holistic processing. This suggests that Alzheimer's leads to visual perception problems specifically with faces. He noted that what was also surprising about this impairment is that it is observed in the early stages of the disease.

The study clarifies the mechanism involved when people with Alzheimer's have trouble recognizing the faces of family members or celebrities. The fact that impaired facial recognition might stem from a holistic perception problem-and not just a general memory problem-opens the door to different strategies (such as the recognition of particular facial traits or voice recognition) to help patients recognize their loved ones for longer.

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