Alcohol Slows the Brain Potential Associated With Cognitive Reaction Time to an Omitted Stimulus

Objective: This study uses a missing stimulus paradigm to investigate cognitive effects associated with moderate blood alcohol levels. Specifically, the rate of rise of the omitted stimulus potential (OSP), which is observed when an expected stimulus is omitted, as well as the peak latency of this potential correlate with cognitive premotor reaction time, and thus might involve similar cognitive processes. An acute dose of alcohol has been found to slow the premotor reaction time to a missing stimulus, but no research has tested alcohol effects on the OSP. Method: A dose of 0.8 g/kg alcohol or a placebo (0 g/kg) was administered in an across-subjects’ design in two groups of 15 young men who were tested on a missing stimulus task before and again after alcohol. During a test, active trials required a response to the missing stimulus, and passive trials required no muscle action. Trials were counterbalanced in each group and obtained measures of premotor reaction time, motor reaction time, OSP onset and delay until muscle action, OSP amplitude, rate of rise, and peak latency. The pretreatment and posttreatment change in a measure assessed the alcohol effect. Results: Compared with placebo, alcohol slowed premotor reaction time, extended the delay of the OSP before muscle action, and slowed the OSP rate of rise and its peak latency. Conclusions: The similarity between alcohol effects on premotor reaction time and some parameters of the OSP supports the importance of examining how other environmental and pharmacological factors known to alter premotor reaction time might change components of the OSP and other types of event-related potentials.