BETHESDA, Md. -- Alcoholism diminishes brain activity related to interpretation of negative emotions, in addition to its adverse effects on cognition, results of a brain imaging study suggest.
BETHESDA, Md., Aug. 27 -- Alcoholism diminishes brain activity related to interpretation of negative emotions, in addition to its adverse effects on cognition, results of a brain imaging study suggest.
MRI evaluation revealed significantly less brain activation during interpretation of facial expressions of fear and disgust by alcoholics versus nonalcoholics, investigators here reported online and in the September issue of Alcoholism: Clinical and Experimental Research.
Alcoholics' brains also had diminished activation during viewing of sad faces, said Jasmin B. Salloum, Ph.D., of the National Institute on Alcohol Abuse and Alcoholism, and colleagues.
The findings may offer a clue to some alcoholics' relapse, they said.
"Patients often relapse when entering previous drinking situations, that is, entering a bar or a shop in which you can buy alcoholic drinks," commented Andreas Heinz, M.D., of Charite-University Medical Center in Berlin, a co-investigator.
"One reason may be that they fail to perceive dangerous situations. This study suggests that there is a neurobiological correlate of this often-reduced ability to perceive dangerous situations," he said
Most studies of the brain effects of alcoholism have focused on cognitive function. However, alcoholics also have been shown to be deficient in emotional processes, but that aspect of brain impairment has not been studied extensively, the authors noted.
In the current study, the investigators used functional MRI to examine brain blood oxygenation level dependent (BOLD) response to emotional stimuli. Previous functional imaging studies had demonstrated increased BOLD activation to negative facial expressions in anxious versus non-anxious individuals.
Other research has shown that alcoholics have blunted response to negative but not positive emotional stimuli, suggesting insensitivity to aversive stimuli.
The study involved 11 male alcoholic patients (mean age 35) and 11 healthy age-matched nonalcoholic males. Both groups underwent functional MRI assessment while performing a task involving emotional processing.
The study participants were asked to determine the intensity level of 240 standardized facial expressions-sad, happy, anger, fear, disgust, and non-emotional control stimuli.
Overall, alcoholic patients demonstrated less brain activation during decoding of all emotions compared with controls. Processing of negative emotions resulted in the largest differences between the groups.
The groups differed significantly with respect to brain activation during interpretation of images reflecting fear, disgust, and sadness. The groups did not differ significantly in the degree of brain activation in response to anger.
The two groups demonstrated similar speed and accuracy in their judgments of emotional intensity, suggesting the differences in performance "reflect different functional approaches to decoding the emotional intensity of human facial expressions taken by alcoholics and controls," the authors stated.
The brain region that showed the greatest blunting of response in the alcoholic patients was the rostral affective division of the anterior cingulate cortex. Some evidence suggests this brain region might be specialized for higher-order cognitive evaluation and decision making related to affective stimuli, the authors noted.
Available evidence also suggests that alcoholics' chronic deficit in social interaction and communication might be caused in part by a diminished ability to interpret the emotional state of others.
"We knew that alcoholics show a deficit in accurate recognition of facial emotions," said Dr. Salloum. "This can lead to insensitivity to, and overestimation and/or misattribution of, certain facial expressions."
The authors pointed out several limitations of the study. "It is a relatively small study involving only 11 subjects in each group. Also, the alcoholic subjects in this study had significant amounts of psychopathology and other substance abuse, they said.
"Thus, it is uncertain if the blunted responses we found in the affective division of the ACC characterize relatively ''pure'' alcoholics as well as they do the more pathological sample we report on here," they wrote.
"In addition, it is unknown whether the deficits we observe in rostral ACC function are secondary to prolonged and heavy alcohol use or precede heavy alcohol use. Studies in young adolescent children of alcoholics may be useful in this regard," they concluded.