Does Reduced Emotional Brain Reactivity After Alcohol Show Better Judgment?

Reduced brain reactivity to emotional pictures does not establish better judgment or fitness to drive. In a placebo-controlled study of 49 social drinkers, alcohol reduced responses in parts of the central extended amygdala. Participants receiving alcohol also performed less accurately on the study’s discrimination tasks.

What the imaging experiment tested

Hur and colleagues randomly assigned participants to alcohol or placebo before functional MRI. The final sample included 27 people receiving alcohol and 22 receiving placebo, mostly in their early twenties. Twelve of the original 61 participants were excluded for imaging, technical, performance or motion problems.

Inside the scanner, participants viewed blocks of faces and places. They distinguished fearful from neutral faces and houses from commercial buildings. The face blocks contained mostly fearful expressions. This was an image-classification task, not a test of a driver’s response to traffic danger.

The alcohol group had a mean breath-derived blood-alcohol equivalent of approximately 0.09%. The exposure was assessed with a breath instrument before and after scanning, rather than a laboratory blood series.

The strongest localized result concerned the BST

In the voxel-based analysis, alcohol significantly reduced the emotional-faces-versus-places response in the left bed nucleus of the stria terminalis, or BST, after correction within the predefined region of interest. No additional clusters met the exploratory whole-brain threshold.

A separate analysis averaged responses within anatomically predefined BST and central-amygdala regions. It found an overall dampening effect at p = .05, without a significant treatment-by-region interaction. That supports a shared pattern; it does not prove that the two regions have identical effects or that every brain area became less active.

The MRI signal reflected blood-oxygenation changes associated with the task. It was not a direct recording of individual neurons, receptor activity or a person’s level of impairment.

Accuracy was lower, not improved

Average discrimination accuracy was 83.2% in the alcohol group and 91.1% in the placebo group, a significant difference of approximately eight percentage points. There was no significant interaction showing that alcohol selectively affected face rather than place accuracy.

Analyses of smaller groups matched for task performance still showed the imaging pattern. This made a simple explanation based entirely on unequal task performance less likely. It did not turn reduced reactivity into a demonstrated functional benefit.

Less reactivity is not a diagnosis of less fear

The authors discussed links to anxiety and alcohol reinforcement. They also noted that fearful-face pictures do not reliably produce strong fear responses and are less naturalistic than moving expressions.

Consequently, the experiment cannot establish that an individual became calmer, perceived road hazards accurately or exercised better judgment. It did not measure driving, collisions or clinical treatment outcomes. Proposed links to stress-related drinking remain interpretations requiring additional studies.

The single-blind design leaves possible experimenter expectations, and the selected young, healthy sample limits generalization. Group-average imaging results cannot retrospectively determine a particular driver’s BAC or explain a specific action.

The site’s hostile-attribution experiment asks a different behavioral question about how faces are interpreted. Keeping that judgment task separate from brain reactivity prevents treating all emotional effects as the same finding.

Primary source

Hur J, Kaplan CM, Smith JF, Bradford DE, Fox AS, Curtin JJ, Shackman AJ. Acute alcohol administration dampens central extended amygdala reactivity. Scientific Reports. 2018;8:16702. https://doi.org/10.1038/s41598-018-34987-3.