If a new study in mice holds true for humans, researchers may have discovered what exactly in the brain turns alcohol abuse to alcohol dependence.
The study, conducted by researchers at the National Institutes of Health, shows that chronic exposure to alcohol seems to move behavior control to the dorsal striatum -- the brain region associated with habit formation -- and away from the prefrontal cortex -- the brain region associated with complex decision-making.
"These findings give important insight into how excessive drinking affects learning and behavioral control at the neural level," Kenneth R. Warren, Ph.D., acting director of the National Institute on Alcohol Abuse and Alcoholism, said in a statement. "The shift to increased striatal control over behavior may be a critical step in the progression of alcoholism."
The study was published in the journal Proceedings of the National Academy of Sciences, and involved brain analysis in mice that were chronically exposed to alcohol vapor.
Researchers found that when the mice were exposed to the alcohol, there was expansion of dendrites -- signal-conducting projections of nerve cells -- in the dorsal striatum brain region. This dendritic expansion seemed to affect the brain's malleability in responding to experiences, as well as receptors known to play a role in sensation and mood.
Interestingly, researchers also found that the mice exposed to the alcohol vapor actually did better at a task that involved decision-making on a touchscreen. "Improved performance on learning tasks that we know depend on the dorsolateral striatum is particularly interesting because it suggests that alcohol could prime the brain to favor other dorsal striatal behaviors -- including things like habit formation, which may foster addictive patterns of behavior," study researcher Dr. Aaron Holmes said in the statement.
Alcohol use disorders -- which include both alcohol dependence (otherwise known as alcoholism) and alcohol abuse -- affect 18 million people in the U.S., according to the National Institute on Alcohol Abuse and Alcoholism. People with alcoholism are physically dependent on alcohol and experience cravings, an inability to stop drinking, and the need to drink higher amounts of alcohol to get the same effect as someone who is not an alcoholic. People who abuse alcohol, on the other hand, may not have the dependency experienced by people with alcoholism, but alcohol use has a negative impact on their everyday lives.
Recently, a Centers for Disease Control and Prevention report showed that excessive alcohol use cost states a median of $2.9 billion in 2006, with binge drinking accounting for most of those costs.