Nov. 29, 2006 Although prior research has looked at brain activity and alcoholism, much of it has focused on cortical activity as a marker for impulsivity among alcoholics. A new study examines measures of brain activity in the frontal regions of the brain, thought to reflect individual differences in emotionality, an important aspect of personality. The discovery of an imbalance of activity in the right and left frontal areas may indicate a dysregulation in brain systems that govern emotion and motivation.
Results are published in the December issue of Alcoholism: Clinical & Experimental Research.
"It is important to see how measures of personality and emotionality relate to alcohol dependence," said Elizabeth P. Hayden, assistant professor in clinical psychology at the University of Western Ontario and corresponding author for the study. "However, most studies of this question use self-report measures of personality and emotional experience. In this paper, we looked at measures of brain activity thought to reflect individual differences in emotional behavior to see whether these were different in a group with alcoholism and other problems [when] compared to control participants."
"An electroencephalogram or EEG is a test that measures electrical activity in the brain," added Emily Grekin, assistant professor of psychology at Wayne State University in Detroit. "Sometimes different brain areas show different patterns of electrical activity, a condition known as EEG asymmetry, which may be a marker of depression. Specifically, individuals with a history of depression have demonstrated lower levels of electrical activity in the front left compared to the front right region of the brain." Yet very little, added Grekin, is known about EEG asymmetry and alcohol dependence. "Dr. Hayden's study is the first to directly address this issue."
Researchers compared resting brain activity in the anterior and posterior cortical regions of 193 individuals who had alcoholism with 108 individuals who did not have a history of psychopathology, including alcoholism. Within the alcoholism group alone, they also examined if a lifetime history of major depressive disorder (MDD) or antisocial personality disorder (ASPD) had effects on regional asymmetry.
"Major depression and antisocial behavior are both problems that commonly co-occur with alcoholism," explained Hayden, "but alcoholics who have these problems may differ [from individuals who do not] in terms of key characteristics related to personality and emotion. Thus, looking at these groups and how they differ on variables of interest may reveal more consistent, clear-cut patterns than looking at alcohol-dependent participants as a whole."
Study results indicate an imbalance in the right and left frontal cortex regions of the brain.
"We found that alcoholics had lower brain activity in left frontal areas relative to right frontal areas, as measured by EEG, when compared to nonalcoholics," said Hayden. "This is interesting because left frontal activity may reflect brain systems involved in acquiring rewards and the positive moods we feel when we obtain a desirable object or goal. Conversely, right frontal activity may be involved in inhibiting behavior in the face of negative consequences and the anxiety we feel in those circumstances." This imbalance, she speculated, may be genetically based -- at least partially.
Echoing Grekin's earlier remarks, Hayden noted that the pattern of asymmetry she found was similar to that found in individuals with depression. "Although this finding dovetails with research that indicates shared genetic influences on these disorders, it is important to note that the difference we found between controls and alcoholic subjects was pretty small," she said.
Nonetheless, said Grekin, "these results are compelling and suggest that EEG asymmetry may be an index of a general vulnerability to psychopathology. Interestingly, participants with both alcohol dependence and depression were found to exhibit less EEG asymmetry than individuals with alcohol dependence alone. These findings are puzzling and warrant further study."
"Our findings probably have the most relevance for understanding vulnerability markers for alcoholism," said Hayden. "We know from research with preschoolers and infants that individual differences in frontal asymmetry may be meaningfully linked to behavior and personality even early in life. It seems likely that these brain measures are trait-like and exist prior to the development of problems. An important next step in this line of research would be to see whether the same is true of frontal brain activity in alcoholism, possibly by looking at the children of alcoholics.
If these patterns of brain activity emerge early in development, we may be able to use these measures -- in conjunction with other information -- to understand who is vulnerable to developing alcoholism."
Alcoholism: Clinical & Experimental Research (ACER) is the official journal of the Research Society on Alcoholism and the International Society for Biomedical Research on Alcoholism. Co-authors of the ACER paper, "Patterns of Regional Brain Activity in Alcohol-Dependent Subjects," were: Ryan E. Wiegand of the Medical University of South Carolina; Eric T. Meyer, Sean J. O'Connor and John I. Nurnberger, Jr. of the Indiana University School of Medicine; Lance O. Bauer of the University of Connecticut School of Medicine; and David B. Chorlian, Bernice Porjesz and Henri Begleiter of the State University of New York Health Science Center at Broolyn. The study was funded by the National Institutes of Health, the National Institute on Alcohol Abuse and Alcoholism, and the National Institute on Drug Abuse.
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