Pre-response theta power was calculated for the −200 to −50 ms time window immediately preceding the motor response, time-locked to button presses (Fig. 4). It showed sensitivity to conflict in the ACC bilaterally only under placebo (left: F(1,19) = 6.6, p<0.02 right: F(1,19) = 6.7, p<0.02), but not alcohol (F(1,19) <0.6, ns). Alcohol reduced the response preparation theta power bilaterally in the ACC (left: F(1,19) = 8.8, p<0.01; right: F(1,19) = 4.4, p<0.05) and the motor cortex (left: F(1,19) = 8.0, p<0.02; right: F(1,19) = 7.0, p<0.02), indicating alcohol-induced impairment of the regions essential for motor preparation and execution. The effect of Beverage X Condition interaction was not significant in any of the ROIs. Theta to INCONG was negatively associated with RTs, r = −0.53, p<0.02, so that lower theta was associated with longer RTs to high-conflict stimuli.
