Academic journal article Alcohol Health & Research World

Monitoring the Brain's Response to Alcohol with Positron Emission Tomography

Academic journal article Alcohol Health & Research World

Monitoring the Brain's Response to Alcohol with Positron Emission Tomography

Article excerpt

Researchers have used positron emission tomography (PET) to study the interrelationships of structural, metabolic, and functional brain changes following alcohol consumption as well as during withdrawal and abstinence. This technique is based on the fact that blood flow and energy metabolism tend to increase in parts of the brain undergoing increased activity and to decrease in brain tissue that is diseased or damaged. PET detects such changes by tracking the distribution within the brain of radioactive chemicals that have been injected into the blood. Because of its sensitivity, PET can detect early functional deficits in the brain before structural changes are apparent. PET has documented gradual recovery of cognitive functions with continued abstinence. In addition, PET data has been used to investigate possible mechanisms for some of alcohol's effects and to provide additional evidence for the heritability of alcoholism. KEY WORDS: brain; AODE (alcohol and other drug effects); positron emission tomography; blood circulation; metabolism; radionuclide imaging; AOD abstinence; AOD impairment; neurotransmission; hereditary factors

Alcoholism1 is associated with a spectrum of cognitive dysfunctions ranging from severe dementing syndromes to more common, subtle disturbances of information processing, problemsolving, and memory (Porjesz and Begleiter 1983; Malloy 1992; Charness 1993). Measurements of blood flow and energy metabolism in the brain are sensitive indicators of such brain function (Volkow and Tancredi 1991). These measurements have been used to identify specific brain regions affected by alcohol and to investigate mechanisms of alcohol-induced cognitive and behavioral impairment.

Researchers have obtained these measurements using various imaging methods, including magnetic resonance imaging (MRI) techniques and single-photon emission computed tomography (SPECT). These methods are described in Mazziotta (1994) and Pfefferbaum and Rosenbloom (1993) and in the article by Doria, pp. 261-265. This article discusses the use of positron emission tomography (PET) to confirm and extend the results of other imaging studies on the interrelationships of structural, metabolic, and functional brain changes following both brief (i.e., acute) and long-term (i.e., chronic) alcohol consumption as well as during withdrawal and abstinence. In addition, the article uses PET data to explore a possible mechanism for some of alcohol's effects to support the heritability of alcoholism.

MONITORING BRAIN FUNCTION WITH PET

Blood flow and energy metabolism tend to increase in parts of the brain undergoing increased activity and to decrease in brain tissue that is diseased or damaged. PET detects these changes by tracking the distribution within the brain of chemicals known as tracers, which are injected into the blood. These tracers are rendered radioactive (i.e., radiolabeled) by being chemically combined with radioactive variants (i.e., radioisotopes) of elements found naturally in the human body. Special cameras surrounding the subject's head track the radioactive tracer as it moves through the brain's bloodstream. A computer translates the resulting data into color-coded images.

PET has had two major applications to date. First, PET can measure blood flow for the entire brain (i.e., cerebral blood flow [CBF]) or for specific regions within the brain (regional CBF [RCBF]). Second, PET can measure brain energy metabolism by tracking the distribution of the radiolabeled tracer fluorodeoxyglucose (FDG), a variation of glucose. Because glucose is normally the brain's sole energy source, the distribution of FDG in the brain reflects relative energy metabolism in different brain regions.

BLOOD FLOW AND BRAIN FUNCTION

Acute exposure to alcohol (e.g., a single drinking session) may produce brain impairments ranging from visible signs of intoxication (e.g., staggering gait) to decreased performance in specialized tests of cognitive function. …

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