"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 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 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 glucose metabolism 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.

Note: If no author is given, the source is cited instead.

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