Academic journal article Alcohol Research

Magnetic Resonance Imaging of the Living Brain: Evidence for Brain Degeneration among Alcoholics and Recovery with Abstinence

Academic journal article Alcohol Research

Magnetic Resonance Imaging of the Living Brain: Evidence for Brain Degeneration among Alcoholics and Recovery with Abstinence

Article excerpt

Alcohol use disorders are characterized by the excessive consumption of alcohol despite its interference with an individual's physical, mental, interpersonal, and social well-being. These harmful behavioral effects are mediated through the brain, which can undergo changes in structure, function, and basic physiology. Some studies (e.g., Cardenas et al. 2007; Gazdzinski et al. 2005x; Pfefferbaum et al. 1995) have shown evidence for recovery with extended sobriety, but some of the brain changes may persist even after extended sobriety, reflecting diminished ability to maintain function when confronted by degenerative processes (i.e., functional reserve) and decreased ability of the brain to change (i.e., plasticity). These persistent alcohol-induced brain changes themselves then may contribute to the self-sustaining nature of alcoholism.

This article reviews studies using three different types of magnetic resonance imaging (MRI)' brain scanning to measure the effects of excessive chronic alcohol consumption on brain size or shape (i.e., macrostructure), tissue quality (i.e., microstructure), and function (i.e., localized blood flow in support of cognitive or motor tasks). To assess the immediate effects of chronic excessive drinking on the brain and cognitive and motor performance, investigators most commonly test alcoholics shortly after they enter treatment and compare them with low-alcohol-consuming study participants (i.e., control subjects) of similar age, sex, and socioeconomic level.

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To test whether the effects of excessive alcohol consumption persist after sobriety is maintained, investigators may compare alcoholics with different lengths of sobriety or preferably follow the same people over time and retest them after varying periods of sobriety. Importantly, these longitudinal studies also require retesting a comparison group of low-alcohol drinkers to control for normal changes in aging and distortion inherent to MRI (i.e., scanner drift) over time. Tests to measure the extent and time-course of such recovery in humans typically are initiated while patients are in alcohol treatment. Such tests track the effects of withdrawal and short-term sobriety. Follow-up studies require tracking patients after discharge, when they have moved back into the community and either maintained sobriety or relapsed into drinking. Longer-term studies therefore take the form of naturalistic rather than controlled experiments because the investigator has no control over whether patients will maintain sobriety or resume drinking and what level of drinking will be embraced. Furthermore, some participants will drop out of the study, affecting the representativeness and size of the follow-up sample.

Even cross-sectional comparisons of problem drinkers with light drinkers must consider that many factors in addition to alcohol consumption may differentiate the groups. Many alcoholic patients also have comorbidities that can affect the brain, including mood disorders, abuse of other substances, and infection from the hepatitis C virus. Thus, investigators performing these studies ideally must screen study participants for these other illnesses and conditions. Furthermore, people with alcoholism may suffer from occult liver disease, malnutrition, and head trauma and are more likely to be chronic smokers than people who are not dependent on alcohol. Each of these factors has its own consequence on the brain (Brody et al. 2004; Gallinat et al. 2006; Grover et al. 2006). Samples of chronic alcoholics also tend to differ from the comparison group of low-alcohol drinkers on variables such as socioeconomic status, mental status prior to onset of alcoholism, and family history of alcoholism (Tarter and Edwards 1986). The amount of alcohol consumed over a lifetime, the pattern of drinking--whether regular or sporadic--and the frequency and intensity of withdrawals also may contribute to how alcohol affects the brain (Anstey et al. …

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