Alcohol consumption affects various behaviors, including motor inhibition. A previous imaging study in humans has shown the reduction of neural activity related to motor inhibition at high alcohol concentration in blood. However, whether lower blood concentration of alcohol would change the neural activity or not has been unknown. Therefore, we conducted functional magnetic resonance imaging (fMRI) study while a stop-signal task (SST) was performed to clarify the change of neural activity at low blood concentration of alcohol.
Seventeen young healthy people participated in the present study under their informed consent. All the participants performed the SST during fMRI scan in two separate days with and without alcohol intake having intervals at least 7 days. The participants took 0.3 g/kg (body weight) of either alcohol or placebo and the fMRI scan started when the breath alcohol concentration (BrAC) went down to 0.20 mg/L.
The go reaction times prolonged at low alcohol level compared to placebo (p = 0.063), while the stop-signal reaction times (SSRTs), which is related to response inhibition, did not differed between alcohol condition and placebo. On the neural level, "stop failure"-related activity increased under alcohol compared to the placebo condition in the bilateral inferior frontal cortex (IFC), while the activity related to "go" and "stop success" in the IFC showed no differences between the alcohol condition and placebo.
We suggest that the low blood concentration of alcohol increases preparatory processes for the task per se but not affects response inhibition. Under low level of blood alcohol, the increased responses in the IFC might be associated with the failure of stop-inhibition.