4/25/2003 - Vanderbilt University Medical Center researchers have discovered that the brain compensates for alcohol-induced damage by recruiting other, unexpected brain regions.
The study, published in the current issue of Alcoholism: Clinical & Experimental Research, is the first to demonstrate this kind of brain activity in alcohol-dependent subjects abstinent for more than two weeks.
The study also confirms that motor deficits are common in alcoholics and may be helpful in increasing our understanding of how the brain adapts to other more-studied neurocognitive deficits associated with chronic alcohol consumption.
Dr. Peter R. Martin, professor of Psychiatry and Pharmacology, director of the Vanderbilt Addiction Center at the Vanderbilt University School of Medicine and corresponding author for the study, used Vanderbilts powerful functional MRI to peer into the brains of abstinent alcoholics and non-alcoholics while the study participants performed a simple motor task finger tapping.
The brains cerebellum and the frontal lobes are known to be the regions most damaged in people with alcoholism and they work in concert to stimulate the body to perform motor activities, Martin said. So, we reasoned that there would probably be abnormalities in activation of these regions in alcoholics during finger tapping, he said.
While undergoing fMRI, two groups of participants performed repetitive, self-paced index finger-tapping exercises: eight (7 male, 1 female) alcohol-dependent patients after approximately two weeks of abstinence; and nine (7 females, 2 males) healthy volunteers acting as controls. Participants alternated between using their dominant hands (DH) and non-dominant hands (NDH) to perform the index finger-tapping exercises. Researchers used fMRI analysis to compare DH and NDH performance in each subject group in order to examine whether the groups differed in the patterns of activation they exhibited in the cerebral cortex and cerebellum.
A normal subject who taps with her right hand activates her left motor cortex and her right cerebellum. The fMRI shows the brain at work by highlighting the active regions in red.
As expected, the detoxified alcohol-dependent patients tapped significantly more slowly than the control group. But researchers were surprised to not see less brain activity. Instead, the fMRI lit up like a city at night to show that alcoholics had a significant increase of activation in both sides of the cerebellum and in the frontal lobes. People with alcoholism had to use more of their brains to do less.
In order to generate a single tap, the brain of a person with alcoholism activates a larger part of their brain than a normal person, even though that person had been sober for over two weeks, Martin said.
This finding is compatible with the idea that different regions of the brain are being called into activity that would not normally be activated in order to meet the behavioral demands. Furthermore, this suggests that even though alcoholics at some level may seem to be performing normally, if you raised the level of complexity at which they are being asked to perform, they may eventually exhaust their capacities ... there may be no more brain to bring in, to recruit, to compensate, Martin said.
Future studies that Martins group has planned will use the new, even more powerful 3-tesla magnet-powered imaging device installed underground, near the Central Library lawn, to study brain activity in people progressing through alcohol recovery.
If we study patients as they progress with their abstinence, do these abnormalities get better? It may be that the brain gets better at compensating, but it doesnt normalize, it just learns how to bring in even more parts of the brain. You could say it learns to rewire itself. Another possibility could be that as the brain heals, less activation is required, and thats a real form of recovery. The answers rest with understanding not the tapping itself, but the mechanisms behind the tapping, Martin said.
Co-authors of the ACER paper were: from the Vanderbilt Addiction Center and the department of Psychiatry research fellow Dr. Mitchell H. Parks, and research coordinator Mark K. Nickel, Ph.D.; from the department of Radiology and Radiological Sciences associate professor David R. Pickens, Ph.D., assistant professor Victoria L. Morgan, Ph.D. and professor Ronald R. Price, Ph.D.; and from Academic Computing and Information Services, Mary S. Dietrich.
The study was funded by the National Institutes of Health, and GE Medical Systems.©2013 Vanderbilt University Medical Center