June 17, 2010

Study shows alcoholics’ brains must work harder to complete some tasks

Study shows alcoholics' brains must work harder to complete some tasks

Alcoholics can perform simple motor tasks, like finger tapping, as competently as those who don’t suffer from alcoholism, but they go about it a slightly different way and their brains have to work harder to complete the task, a Vanderbilt University Medical Center study shows.

The Alcoholism: Clinical and Experimental Research study compared 10 patients who met the “Diagnostic and Statistical Manual of Mental Disorders (DSM-IV)” criteria for alcohol dependence with 10 closely matched healthy control subjects. The alcoholic patients had been abstinent for at least 10 days and were over withdrawal.

They were asked to perform finger tapping in two ways – once, as rapidly as they possibly could, and again, at a slower rate, when a white arrow on a TV screen alerted them to tap. Their brains were scanned by Functional Magnetic Resonance Imaging (fMRI) as they tapped.

“Our strategy was to take a task we knew the alcoholic could perform as well as the normal population, and to use fMRI to try to figure out what was going on in their brains while they were performing that task,” said Peter Martin, M.D., professor of Psychiatry and principal investigator of the study.

Peter Martin, M.D.

Peter Martin, M.D.

The study found no difference in the number of taps each group achieved.

Once the finger tapping was averaged out, the alcoholic group was identical to the normal control sample. However, there was considerably more variability in how the alcoholics tapped compared to the controls.

“They (the alcoholic group) weren’t as consistent or accurate,” Martin said. “It’s almost like they tapped as fast as they could, then slowed down, then started up again to make up for lost time, but the number of times they tapped was identical,” he said.

But the most visible difference in comparing the two groups was the regions of the brain activated to perform the task. The alcoholic group required more brain activation to accomplish the same number of taps per minute.

They activated all the brain regions activated by the normal group, mostly the cerebellar frontal circuits (the connection between the cerebellum and the frontal lobes), plus some additional areas that the control subjects didn’t use – the inferior frontal cortex and the parietal lobe.

Inferior frontal activation is the brain region needed for planning, organization, and impulse regulation and the parietal lobes are required for visuospatial performance.

“They brought into play large, additional parts of their brain to accomplish the task,” Martin said. “It’s like they were using a bulldozer rather than a shovel on a rose bush.

“What we realize from this is that when the alcoholic group is performing something simple, they are working very hard, indeed, and as soon as the task becomes more complicated, they are destined to fail,” Martin said. “Their brain flexibility is impaired and their capacity to mount more difficult performances is compromised.”

Martin said that more studies like these should be performed. “By looking at how alcoholics perform these simple tasks, we can figure out what’s wrong with their brains and perhaps use these abnormalities as the focus for treatment in future studies, to help them obtain a more effective and fulfilling life,” he said.

Also participating in the study were Mitchell Parks, M.D., assistant professor of Psychiatry at Meharry Medical College and Vanderbilt, Mary Dietrich, Ph.D., research associate professor of Nursing, and Baxter Roger, Ph.D., research assistant professor of Radiology and Radiological Sciences.