New research published in the Journal of Alzheimer’s Disease sheds light on why those with dementia lose their ability to recognize faces and finds that it’s not due to a general memory problem.

The knowledge may be helpful in developing strategies, such as facial trait or voice recognition, that those with the disease can use to recognize their loved ones for a longer period of time, according to Sven Joubert, Ph.D., a geriatrics researcher and professor with the Department of Psychology at the University Montreal, and colleagues.

The ability to detect and identify faces is thought to depend on one’s ability to perceive a face as a whole rather than individual facial features such as the eyes, nose or mouth. The study by Joubert and colleagues, however, found that Alzheimer’s disease impairs a person’s holistic ability to perceive faces. They reached their conclusion by studying the ability of healthy seniors and those with Alzheimer’s to perceive faces and cars in photos that were either upright or upside down.

“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,” Joubert said. With the upright faces, however, he added, people with Alzheimer’s disease were much slower and made more mistakes than study participants without the disease. Those with Alzheimer’s disease did not have difficulty with the upright photos of cars; that task, in theory, does not involve the holistic processing required with faces, Joubert said.

“This suggests that Alzheimer’s leads to visual perception problems specifically with faces,” he said, adding that researchers were surprised that the impairment occurs in the early stages of the disease.