Researchers at the University of California, Davis say patients with Alzheimer's disease have difficulty recognizing facial emotions.

The researchers examined Alzheimer's patients, healthy elderly volunteers, and elderly, non-demented psychiatric outpatients, testing three measures -- facial emotion matching, facial emotion labeling, and same-different emotion differentiation.

In each area, the Alzheimer patients were "significantly impaired" when compared to the control groups.

Moreover, Alzheimer patients also had problems matching facial identities, suggesting that the inability to process facial emotion may be independent of the inability to process nonemotional features of the face.

Another significant finding was the patients' selective difficulty in labeling facial expressions of sadness.

"This may also help explain some of the interpersonal difficulties that some Alzheimer patients are prone to," said Dr. Rita Hargrave, the study's lead author. "If you don't have awareness, you'll keep doing (or saying) what you're doing."

Based on her finding, Hargrave said she hopes researchers will be prompted to take her study a few steps further.

"I would recommend that future researchers (gauge responses) which look at body language, movement, tone of voice, etc.," she said. "We're looking at static images - MRIs, CTscans. But (researchers) could use some of the same tests, and add PET scans, to examine brain activity, as well."

Other sources: Journal of Neuropsychiatry, UC Davis