January 1, 2000
UPTON, NY - How does aging affect the brain? Researchers from the U.S. Department of Energy's Brookhaven National Laboratory, the State University of New York at Stony Brook and the University of Pennsylvania School of Medicine have found chemical changes in the brain that may underlie the cognitive deterioration associated with aging. The results of their experiment will be reported in the January 2000 issue of The American Journal of Psychiatry.
"In this study, we have shown that age-related loss of dopamine, the brain chemical associated with pleasure and reward, slows metabolism in regions of the brain that are related to cognition. This finding may be helpful in developing interventions for age-related cognitive decline," said Dr. Nora Volkow, Brookhaven's Associate Laboratory's Director for Life Sciences and the lead author of the study.
The researchers found that age is associated with a significant decline in dopamine D2 receptors - molecules that transmit signals that are associated with pleasure and reward in the brain. Approximately six to seven percent of these receptors are lost with each decade of age, from 20 to 80 years. This decrease in dopamine with aging has been corroborated by other studies performed by Volkow and others. In the current investigation, for the first time, researchers discovered that when dopamine D2 receptors decreased, so did regional glucose metabolism in areas of the brain that are related to cognition.
In the group of healthy participants, glucose metabolism decreased with age in the frontal brain regions and in a part of the brain known as the anterior cingulate gyrus. Decreased glucosemetabolism translates to decreased brain activity, or deterioration of brain function. The frontal brain region controls such functions as problem-solving, the ability to think abstractly, and the ability to carry out multiple tasks simultaneously. The anterior cingulate gyrus is related to attention span, impulse control and mood.
The correlation between dopamine availability and brain metabolism remained significant after removing age effects in this investigation, which suggests that dopamine may influence brain metabolism regardless of age. (While dopamine declines with age in general, it is not always the case, and some younger people may have less dopamine than some older individuals.)
The research was carried out using an imaging technique known as positron emission tomography. The researchers measured dopamine D2 receptors and glucose metabolism in the brains of 37 healthy subjects, 24 to 86 years old. No participant took medication during the time of the study, and all participants were screened for psychoactive drug use.
This study was funded by the U.S. Department of Energy and the National Institute on Drug Abuse. It was carried out following guidelines set forth by the Institutional Review Board at Brookhaven National Laboratory, which regulates experiments on humans.
The U.S. Department of Energy's Brookhaven National Laboratory creates and operates major facilities available to university, industrial and government personnel for basic and applied research in the physical, biomedical and environmental sciences, and in selected energy technologies. The Laboratory is operated by Brookhaven Science Associates, a not-for-profit research management company, under contract with the U.S. Department of Energy.
NOTE TO LOCAL EDITORS: Nora Volkow is a resident of Shoreham, N.Y.