Excessive, chronic drinking can lead to brain damage on multiple levels, including the development of emotional abnormalities that can interfere with healthy interpersonal relationships. Findings from a recent study using functional magnetic resonance imaging (fMRI) suggest that diminished activity of the amygdala and hippocampus underlie emotional impairments observed in abstinent long-term alcoholics.
Results will be published in the November issue of Alcoholism: Clinical & Experimental Research and are currently available at Early View.
"Like most body organs, the brain is vulnerable to injury from excessive alcohol consumption," said Ksenija Marinkovic, assistant professor in residence in the radiology department at the University of California, San Diego. "Risk of brain damage and related neurobehavioral deficits vary from person to person, depending on a wide range of factors such as the amount and duration of drinking, age, gender, family history of alcoholism, and overall health. Most common deficits include difficulties with memory, reduced reasoning and problem solving abilities, and emotional abnormalities."
Alcoholism-related emotional abnormalities can be subtle, Marinkovic explained, such as misperceiving facial and verbal cues, or obvious, such as emotional flatness and apathy, or sudden outbursts of anger.
"Alcoholics also have problems in judging the emotional expressions on people's faces," she added. "This can result in miscommunication during emotionally charged situations and lead to unnecessary conflicts and difficulties in interpersonal relationships. The resulting negative repercussions can, in turn, contribute to increased drinking."
For this study, researchers used fMRI technology to examine two groups of men matched on socioeconomic backgrounds, age, education, and IQ: 15 abstinent long-term alcoholics and 15 healthy, nonalcoholic controls. While in the scanner, participants were presented with positive, negative, or neutral words and photographs of faces. These were divided into two different kinds of encoding. One was "deep" or semantic, such as classifying a word as abstract or concrete, or rating a face for intelligence, thereby leaving a robust memory trace; and the other was "shallow" or perceptual, such as the simple classification of color vs. no color, leaving a weak memory trace.
In parts of the temporal lobes of the brain called the amygdala and hippocampus, faces evoked stronger activation than words, especially in the deep encoding testing. "The amygdala normally responds to face expressions, and the hippocampus is involved in remembering them. In addition, faces are more visually complex stimuli, which could have had a bearing on increased activity in the amygdala and hipppocampus," Marinkovic explained.
"The neuroimaging evidence from our study suggests that deficient activation of limbic structures inside the temporal lobes – the amygdala and hippocampus – may underlie emotional difficulties in abstinent long-term alcoholics," said Marinkovic. "Whereas nonalcoholic adult men showed stronger activation in the amygdala and hippocampus when viewing faces with emotional expressions, the alcoholics showed decreased activation in these brain areas, and furthermore responded in an undifferentiated manner to all facial expressions. The alcoholics also were impaired on the intelligence-appraisal task, possibly due to their dampened amygdala activity."
"In addition," said Edith V. Sullivan, professor in the department of psychiatry and behavioral sciences at Stanford University School of Medicine, "unlike the controls, the alcoholics recruited the prefrontal cortex while processing facial emotions, perhaps compensating for dampened activation of neural centers, such as the amygdala and hippocampus, which are normally invoked for such processing."
Use of a different neural "route" to process the same facial emotional information presented to controls is consistent with other fMRI studies, Sullivan added, which have demonstrated that alcoholics can invoke additional and sometimes higher-order brain systems to accomplish a relatively simple task at normal levels.
Marinkovic said these findings are also in agreement with prior studies showing amygdala hypoactivity in psychopathy and also in individuals with a family history of alcoholism, particularly those with more disinhibited traits. "Amygdala hypoactivity may underlie emotional dysfunction in chronic alcoholics … and be a part of a wide array of behavioral problems, including disinhibition and disregard for social norms," she said.
"Viewed in their totality," said Sullivan, "these results show that not all facial expressions are necessarily perceived the same by everyone, and that alcoholics may be at a special disadvantage in detecting emotion-filled facial expression, which we all naturally use to convey information, such as warnings, love, anger, and defense, among others, and assume that the intended message is accurately perceived. Whether the differences between controls and alcoholics in brain activation existed before the onset of alcoholism, or are the result of neural circuitry changes or differences in blood perfusion caused by chronic alcohol consumption, intoxication or withdrawal, remain as questions to be answered."
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