Alcoholics are more impulsive than non-addicted people making financial decisions, revealed by researcher Charlotte Boettiger at the University of North Carolina at Chapel Hill.
The researchers also discovered that a specific gene mutation boosted activity in these brain regions when people made impulsive choices. The mutation was already known to reduce brain levels of the neurotransmitter dopamine. The newly found link involving the gene, impulsive behavior and brain activity suggests that raising dopamine levels may be an effective treatment for addiction, the scientists say.
The research is reported in the Dec. 26, 2007 issue of the “Journal of Neuroscience.”
Lead scientist is Charlotte Boettiger, PhD, assistant professor of psychology at the University of North Carolina at Chapel Hill. Boettiger led the research as a scientist at UCSF’s Ernest Gallo Clinic and Research Center. Senior author is Howard Fields, MD, PhD, a UCSF professor of neurology and an investigator in the Gallo Center. He also serves as director of the UCSF Wheeler Center for the Neurobiology of Addiction.
“Our data suggest there may be a cognitive difference in people with addictions,” Boettiger said. “Their brains may not fully process the long-term consequences of their choices. They may compute information less efficiently.”
“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.
“I am very excited about these results because of their clinical implications,” Fields said. “The genetic findings raise the hopeful possibility that treatments aimed at raising dopamine levels could be effective treatments for some individuals with addictive disorders.”
The scientists used functional magnetic resonance imaging, or fMRI, to image brain activity while subjects were faced with a hypothetical scenario: choose less money now, or more money later.
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. People who sustain damage to the orbital frontal cortex generally suffer impaired judgment, manage money poorly and act impulsively, the scientists noted.
The study revealed 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. The orbital frontal cortex activity may be a neural equivalent of long-term consequences, Fields said.
“Think of the orbital frontal cortex as the brakes,” Boettiger explained. “With the brakes on, people choose for the future. Without the brakes they choose for the short-term gain.”
The frontal and parietal cortexes are also involved in working memory ? being able to hold data in mind over a short delay. When asked to choose between $18 now or $20 in a month, the subjects had to calculate how much that $18 (or what it could buy now) would be worth in a month and then compare it to $20 and decide whether it would be worth the wait. The parietal cortex and the dorsal prefrontal cortex were much more active in people unwilling to wait. This could mean, Boettiger said, that the area is working less efficiently in those people.
Co-authors on the paper are: Jennifer Mitchell, Vanessa Tavares, Margaret Roberston and Geoff Joslyn at the Gallo Center, and Mark D’Esposito at the University of California, Berkeley.
The research was supported by the U.S. Department of Defense and the UCSF Wheeler Center for the Neurobiology of Addiction.
UCSF is a leading university dedicated to defining health worldwide through advanced biomedical research, graduate level education in the life sciences and health professions, and excellence in patient care.
UCSF’s Gallo Clinic and Research Center is a preeminent academic center for the study of the biological basis of alcohol and substance abuse.
Source: University of California, San Francisco, USA