Wednesday, December 26, 2007

People addicted to alcohol more impulsive in their decision-making

New research involving brain imaging and genetic studies has for the first time established an association between thinking patterns and liquor addiction.

Published in the Journal of Neuroscience, the study was based on a comparison between brain activity of sober alcoholics and non-addicted people, while they made financial decisions.

It showed that sober alcoholics tended to show significantly more "impulsive" neural activity in some areas of the brain, as they made financial decisions. The study also discovered that a specific gene mutation boosted activity in these brain regions when people made impulsive choices.

Lead researcher Dr. Charlotte Boettiger, assistant professor of psychology at the University of North Carolina at Chapel Hill, says that this mutation is already known to reduce brain levels of the neurotransmitter dopamine.

"Our data suggest there may be a cognitive difference in people with addictions. Their brains may not fully process the long-term consequences of their choices. They may compute information less efficiently," said Boettiger, who led the study as a scientist at UCSF's Ernest Gallo Clinic and Research Center.

"What's exciting about this study is that it suggests a new approach to therapy. We might prescribe medications, such as those used to treat Parkinson's or early Alzheimer's disease, or tailor cognitive therapy to improve executive function," she added.

Dr. Howard Fields, the senior author of the study, said that the newly found link involving the gene, impulsive behaviour and brain activity suggests that raising dopamine levels may be an effective treatment for addiction.

"I am very excited about these results because of their clinical implications. The genetic findings raise the hopeful possibility that treatments aimed at raising dopamine levels could be effective treatments for some individuals with addictive disorders," Fields said.

During the study, the subjects were asked either to choose less money then and there or to get more money later. Their brain activity was scanned using functional magnetic resonance imaging (fMRI), as the participants made their choices.

The researchers revealed that while decisions were being made, the imaging detected activity in the posterior parietal cortex, the dorsal prefrontal cortex, the anterior temporal lobe and the orbital frontal cortex.

They said that sober alcoholics tended to chose the "now" reward almost three times more often than the control group, reflecting more impulsive behaviour.

The authors noted that the imaging detected reduced activity in the orbital frontal cortex in the brains of subjects who preferred "now" over "later", most of whom had a history of alcoholism.

"Think of the orbital frontal cortex as the brakes. With the brakes on, people choose for the future. Without the brakes they choose for the short-term gain," Boettiger said.

The dorsal prefrontal cortex and the parietal cortex often form cooperative circuits, and the study found that high activity in both is associated with a bias toward choosing immediate rewards.

The study also showed that people with two copies of the mutation in a gene called COMT, which is associated with lower dopamine levels, had significantly higher frontal and parietal activity, and chose "now" over "later" significantly more often.

"We have a lot to learn. But the data takes a significant step toward being able to identify subtypes of alcoholics, which could help tailor treatments, and may provide earlier intervention for people who are at risk for developing addictions," Boettiger said.

source: Journal of Neuroscience

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