NIH study finds chronic alcohol use shifts brain’s control of behavior
Chronic alcohol exposure leads to brain adaptations that shift behavior control away from an area of the brain involved in complex decision-making and toward a region associated with habit formation, according to a new study conducted in mice by scientists at the National Institutes of Health.
The finding provides a biological mechanism that helps to explain compulsive alcohol use and the progression to alcohol dependence. A report appears online in the Proceedings of the National Academy of Sciences (PNAS).
The brain’s prefrontal cortex is involved in decision-making and controlling emotion, while the dorsal striatum is thought to play a key role in motivation and habit formation. Past studies have shown that alcohol dependent individuals show problems with skills mediated by the prefrontal cortex such as impulse control. These same individuals often show exaggerated neural response in the dorsal striatum to alcohol-related cues.
To investigate whether changes in the dorsal striatum might account for these observations, researchers led by Andrew Holmes, Ph.D., in the Laboratory of Laboratory of Behavioral and Genomic Neuroscience at NIAAA, measured changes in the brains of mice that were chronically exposed to alcohol vapors.
He and his colleagues found profound changes in the dorsal striatum of these mice, including the expansion of neuronal dendrites, the branching projections of the nerve cell that conduct signals. Such changes are also seen with chronic exposure to drugs such as amphetamine. These structural changes were associated with changes in synaptic plasticity, the brain’s ability to change in response to experience, and reduced activity of endocannabinoid receptors, which are part of a signaling system that may play a role in sensation, mood, and memory.
“These findings give important insight into how excessive drinking affects learning and behavioral control at the neural level,” said Kenneth R. Warren, Ph.D., acting director of the National Institute on Alcohol Abuse and Alcoholism (NIAAA). “The shift to increased striatal control over behavior may be a critical step in the progression of alcoholism.”
“The changes we observed suggest that the manner in which the dorsal striatum signaled and adapted to environmental information has been altered by alcohol,” said senior author Dr. Andrew Holmes. “The findings imply that chronic drinking may set up a concerted set of adaptions in this key brain region that produce a bias for striatal control over behavior.”
