Alcohol breaks down interhemispheric inhibition in females but not in males

Alcohol has renowned behavioral disinhibitory properties which are suggested to involve reductions in frontal lobe functioning as a result of diminished interhemispheric connectivity. To examine sex differences in frontal interhemispheric connectivity in response to alcohol, 12 female and ten male healthy volunteers received a single administration of 0.5aEuro degrees alcohol in a placebo-controlled counterbalanced crossover design. Paired-pulse transcranial magnetic stimulation was applied to measure transcallosal inhibition (TCI) between the left and right primary motor cortex (M1). Results showed significant reductions in TCI after alcohol administration in female participants exclusively. These findings provide the first evidence that moderate doses of alcohol differentially affect frontal interhemispheric connectivity in males and females. The present data may shed new light on the physiological mechanisms underlying sex differences in the susceptibility to alcohol.