Effects of moderate and high doses of alcohol on attention, impulsivity, discriminability, and response bias in immediate and delayed memory task performance

Background: Prior studies that examined the effects of alcohol on Continuous Performance Test (CPT) performance have resulted in inconsistent outcomes. Most studies that examined the effects of alcohol on concentrated attention tasks (like the CPT) found little effect of alcohol on performance measures, even when doses that exceeded 0.8 g/kg were used. One likely reason for these inconsistencies is the varying difficulty (and sensitivity) of the task used, and as a result, comparisons between studies are difficult. This study is one in a series that examines the effects of alcohol on attention by using a difficult version of the CPT (Immediate and Delayed Memory Task-IMT/DMT). Our purpose for these studies has been twofold, examining the effects of alcohol (1) on concentrated attention (i.e., correct detections) and (2) on errors (i.e., commission errors) previously correlated with impulsive behaviors. The first is important because previous studies have shown little effect of alcohol on attention, and the second is important because commission errors have been related to impulsive behaviors. Methods: In the IMT/DMT, participants respond to a briefly displayed number when it is identical to the one displayed before it. The procedure includes immediate and delayed conditions where successive stimuli to be matched are delayed by 0.5 sec or by 3.5 sec. The three stimulus types included target (identical match), catch (four of five digits match), and filler (no match) stimuli. Twenty subjects completed this task after consuming either a placebo drink or a drink that contained 0.5 g/kg or 1.0 g/kg of alcohol on different days. Results: The main findings were that (1) alcohol decreased the percentage of correct identifications of target stimuli; (2) alcohol increased the percentage of commission errors in relation to the number of correct target responses; and (3) alcohol decreased discriminability whereas response bias became more conservative. Conclusions: These results clearly demonstrated a time-course effect of the 1.0 g/kg alcohol dose on attention, impulsivity, discrimination, and response criteria when a variety of dependent measures are used.