Study: Decrease in Arousal May Play Role in Alzheimer's Disease

A decrease in the ability to become aroused appears to play a role in Alzheimer's disease and other mental and emotional disorders, according to a study reported in the Aug. 11 issue of the Proceedings of the National Academy of Sciences.

Arousal is thought to be the base of all emotionally laden behaviors. Scientists who study arousal historically were divided into two camps: those who consider arousal to be a single, monolithic physiological function and those who believe that arousal does not exist as a whole, but is a collection of small specific abilities.

In the study, Donald W. Pfaff, who heads the Laboratory of Neurobiology and Behavior at Rockefeller University in New York, and his colleagues developed a mathematical equation that for the first time unifies these two differing schools of thought. They also found a way to measure arousal in laboratory mice.

The researchers believe that an aroused human is more sensitive to sensory stimuli, more physically active and more emotional than an unaroused human. They also found that a generalized aroused state exists and that the expression of specific genes can influence arousal.

The existence of a generalized arousal function is not exclusive of several specific forms of arousal," says Pfaff. "For example, if you scare the heck out of me, I'm more likely to react strongly if I'm generally aroused anyway, whereas if I'm asleep, I'm just a bit sluggish in my response."

A decrease in people's ability to become aroused may account for some of the mental difficulties that people face as they age, according to the study.

The researchers also believe that deficits in arousal contribute to such cognitive problems as attention deficit hyperactivity disorder, autism and Alzheimer's disease.

Other sources: Rockefeller University