Protracted impairment of impulse control under an acute dose of alcohol: a time-course analysis.

Alcohol is well-known for impairing impulse control as well as its disruptive effects on other aspects of behavioral functioning, such as motor control. Time-course analyses during a single dose show rapid development of acute tolerance to impairment of motor coordination, reaction time, and levels of subjective intoxication, but no acute tolerance to impairment of the ability to inhibit responses. Evidence for a possible lag in tolerance development to the impairing effects of alcohol on inhibitory control suggests that, as drinkers' blood alcohol concentration (BAC) declines, they might exhibit prolonged impulsivity despite having an unimpaired ability to initiate action. The present study extended the time-course analysis to examine the recovery of inhibitory control under a dose of alcohol as drinkers' BAC descended from a peak of 80 mg/100ml to a zero level. Twenty-four healthy adults were tested following 0.65 g/kg alcohol and a placebo in a counterbalanced order. They performed a cued go/no-go task that measured response inhibition. They also performed tasks that assessed reaction time, motor coordination, and completed ratings of their subjective levels of intoxication. Alcohol initially impaired inhibitory control, response time, and motor coordination and increased subjective ratings of intoxication. However, acute tolerance to the impairing effects of alcohol was observed for measures of response time, motor coordination, and ratings of intoxication and these measures returned to sober (i.e., placebo) levels by the time BAC fell to near zero. By contrast, impairment of inhibitory control showed no acute tolerance and remained impaired even when drinkers' BAC returned to near zero. Taken together, these results indicate that the disinhibiting effects of alcohol are present even when the impairing effects of alcohol on other aspects of behavior have diminished under the dose. These findings could provide a greater understanding of impulsive behaviors during the descending limb of intoxication.