Alcoholism and the brain: an overview

Alcohol Research & Health, Spring, 2003 by Marlene Oscar-Berman, Ksenija Marinkovic

Gender: Although it has been hypothesized that women's brain functioning is more vulnerable to alcoholism than men's, studies of gender differences have not consistently found this to be true (see Wuethrich 2001 for a review), even though women and men metabolize alcohol differently (i.e., women achieve higher blood alcohol contents [BACs] than men after consuming the same amount of alcohol). However, it is not known whether this comparison between men and women holds among older populations (Oscar-Berman 2000).

Family History. Family history of alcoholism has been found to be important because it can influence such things as tolerance for alcohol and the amount of consumption needed to feel alcohol's effects. Also, studies examining brain functioning in people with and without a positive family history of alcoholism have shown that there are clear differences between the groups on measures of brain electrical activity (Porjesz and Begleiter 1998).

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Vitamin Deficiency. Research on malnutrition, a common consequence of poor dietary habits in some alcoholics, indicates that thiamine deficiency (vitamin [B.sub.1]) can contribute to damage deep within the brain, leading to severe cognitive deficits (Oscar-Berman 2000). The exact location of the affected parts of the brain and underlying neuropathological mechanisms are still being researched (see the next section).

Models Based on Vulnerable Brain Systems

The outer, convoluted layer of brain tissue, called the cerebral cortex or the gray matter, controls most complex mental activities (see figure 1). Just beneath it are the nerve fibers, called the white matter, that connect different cortical regions and link cortical cells with other structures deep inside the brain (subcortical regions).

Areas of the brain that are especially vulnerable to alcoholism-related damage are the cerebral cortex and subcortical areas such as the limbic system (important for feeling and expressing emotions), the thalamus (important for communication within the brain), the hypothalamus (which releases hormones in response to stress and other stimuli and is involved in basic behavioral and physiological functions), and the basal forebrain (the lower area of the front part of the brain, involved in learning and memory) (Oscar-Berman 2000). Another brain structure that has recently been implicated is the cerebellum (Sullivan 2000), situated at the base of the brain, which plays a role in posture and motor coordination and in learning simple tasks.

Alcohol-Related Brain Atrophy.

According to one hypothesis, shrinkage (i.e., atrophy) of the cerebral cortex and white matter, as well as possible atrophy of basal forebrain regions, may result from the neurotoxic effects of alcohol (Lishman 1990). Furthermore, thiamine deficiency may result in damage to portions of the hypothalamus (perhaps because blood vessels break in that region). According to this hypothesis, alcoholics who are susceptible to alcohol toxicity (2) may develop permanent or transient cognitive deficits associated with brain shrinkage. Those who are susceptible to thiamine deficiency will develop a mild or transient amnesic disorder, with short-term memory loss as the salient feature. Patients with dual vulnerability, those with a combination of alcohol neurotoxicity and thiamine deficiency, will have widespread damage to large regions of the brain, including structures deep within the brain such as the limbic system. These people will exhibit severe short-term memory loss and collateral cognitive impairments (Oscar-Berman 2000).