Academic journal article Alcohol Research

Positron Emission Tomography: A Tool for Identifying the Effects of Alcohol Dependence on the Brain

Academic journal article Alcohol Research

Positron Emission Tomography: A Tool for Identifying the Effects of Alcohol Dependence on the Brain

Article excerpt

To study alcohol's effects on the structure and function of the brain in living human beings, researchers can use various imaging techniques. Positron emission tomography (PET) is a functional imaging approach used to study the metabolism and physiology of the brain. PET studies have found that both acute and chronic alcohol ingestion alter blood flow and metabolism in various brain regions, including the frontal lobes and cerebellum. Other analyses focusing on alcohol's effects on brain chemical (i.e., neurotransmitter) systems have found that both acute and chronic alcohol consumption alter the activities of the inhibitory neurotransmitter gamma-aminobutyric acid (GABA) and the excitatory neurotransmitters glutamate, dopamine, and serotonin. These alterations may contribute to the reinforcing and rewarding effects of alcohol as well as to symptoms of alcohol withdrawal. Imaging studies also have demonstrated that some of alcohol's adverse effects on brain function can be reversed by abstinence or alcoholism treatment interventions. In addition, imaging studies may help in the development of new medications for alcoholism treatment.

KEY WORDS: positron emission tomography; chronic AODE (alcohol and other drug effects); neurobiological theory of AODU (alcohol and other drug use); AOD dependence; brain reward pathway; neuroimaging; excitatory neurotransmitters; hyperexcitability; GABA receptors; glutamate; dopamine; mesolimbic system; serotonin; endogenous opioids; glucose metabolism; cerebral blood flow; AODR (alcohol and other drug related) structural brain damage

Alcohol exerts profound and harmful effects on the human nervous system. One way of determining how the brain is affected by alcohol consumption-particularly chronic excessive consumption that has led to alcohol dependence-is to look directly at the brain and its structures. Obviously, these examinations can be performed only during autopsies of deceased alcoholics. Investigations of the progression of alcohol-induced brain damage over time, its reversibility with abstinence, and the effectiveness of pharmacological and other interventions, however, require analyses in living subjects who can be studied repeatedly. Over the past few decades, various imaging techniques have been developed that allow researchers to study the structure and function of the brain both in healthy people and in people with alcoholism or other disorders. By allowing investigators to visualize alcohol's actions on the brain in living human beings, these techniques are essential tools for documenting alcohol-induced damage as well as the effects of interventions for alcoholism.

This article focuses primarily on the contributions of one imaging technique-positron emission tomography (PET)-to the analysis of alcohol-related brain damage. Following a description of PET technology, the article explores how this approach has helped elucidate alcohol's effects on the structures and functions of the brain, particularly its effects on various brain chemical (i.e., neurotransmitter) systems. Methodological considerations relevant to applying PET technology to studies of alcohol dependence also are discussed.

PET AND OTHER NEUROIMAGING TECHNIQUES

The various techniques to visually represent the nervous system that have been developed over the past few decades generally fall into two broad categories, structural and functional imaging approaches. Structural neuroimaging techniques, such as computerized tomography1 (CT), magnetic resonance imaging (MRI), and an MRI subtype known as diffusion tensor imaging (DTI), illustrate the anatomy of the nervous system. In alcohol research, these approaches are ideally suited for demonstrating anatomical changes that alcohol causes in the nervous system. In contrast, functional neuroimaging procedures-such as PET, functional MRI, magnetic resonance spectroscopy (MRS), and single photon emission computerized tomography (SPECT)-show the metabolic and physiologic processes of the nervous system in action. …

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