TUESDAY, July 13 (HealthDay News) -- Patients with Alzheimer's disease often can seem withdrawn and apathetic, symptoms frequently attributed to memory problems or difficulty finding the right words.

But patients with the progressive brain disorder may also have a reduced ability to experience emotions, a new study suggests.

When researchers from the University of Florida and other institutions showed a small group of Alzheimer's patients 10 positive and 10 negative pictures, and asked them to rate them as pleasant or unpleasant, they reacted with less intensity than did the group of healthy participants.

"For the most part, they seemed to understand the emotion [normally evoked from the picture they were looking at]," said Dr. Kenneth Heilman, senior author of the study and a professor of neurology at the University of Florida's McKnight Brain Institute. But, he added, their reactions were different from those of the healthy participants.

"Even when they comprehended the scene, their emotional reaction was very blunted," he said. The study is published online in the Journal of Neuropsychiatry and Clinical Neurosciences.

The study participants -- seven with Alzheimer's and eight without -- made a mark on a piece of paper that had a happy face on one end and a sad one on the other, putting the mark closer to the happy face the more pleasing they found the picture and closer to the sad face the more distressing.

Compared to the healthy participants, those with Alzheimer's found the pictures less intense.

They didn't find the pleasant pictures (such as babies and puppies) as pleasant as did the healthy participants. They found the negative pictures (snakes, spiders) less negative.

"If you have a blunted emotion, people will say you look withdrawn," Heilman said.

One important take-home message, he added, is for families and physicians not to automatically think a patient with blunted emotions is depressed and ask for or prescribe antidepressants without a thorough evaluation first.

Exactly why this blunting of emotions may occur isn't known, Heilman said. He speculates there may be a degradation of part of the brain or loss of control of part of the brain important for experiencing emotion. Or a neurotransmitter important for experiencing emotion may undergo degradation.

What the finding suggests is that as the memory goes, so does some emotion, said Dr. Gary Kennedy, a geriatric psychiatrist at Montefiore Medical Center in New York City, who reviewed the findings.

"Emotion and memory go together," he said. "The more emotion you can attach to an event, the more likely you are to remember. I think what this paper is telling us is that the disease is causing the emotional response to become more and more shallow over time."

Apathy seen in Alzheimer's patients is often reported by family members, Kennedy said. "Apathy is a heartbreaker for the family," he said.

Even so, both Kennedy and Heilman had a positive message for family members. For family, it's not to take it personally if a loved one with Alzheimer's is apathetic. "Don't interpret it as being done willfully," Kennedy said.

Heilman said families can try to make information more explicit when talking to those with Alzheimer's, in an effort to help emotions kick in. If you show a loved one a picture, for instance, give verbal details about the person or object in it, he suggested. You may see less apathy in response.

The research was supported in part by Lundbeck Pharmaceutical Co., whose products include Alzheimer's medicine.

More information

To learn more about the stage of Alzheimer's disease, visit the Alzheimer's Association.