The effect of repeated occasions of alcohol intoxication on two processes involved in the visual discrimination of movement.

The focus of this study was the effect of repeated episodes of alcohol intoxication on two processes involved in visual movement discrimination: visual sensitivity and decision-making. Four female subjects were asked to discriminate between a stationary light signal and one that changed position in the center of a dark visual field. Prior to each of 15 alcohol testing sessions, a dose of .66 ml of 95% USP ethanol per kg body weight was administered to each subject and BAL was sampled frequently within sessions. Differences in subjects' pre- and postalcohol performance were evaluated within the framework of a psychophysical model that mathematically characterizes the problem of movement discrimination and yields independent estimates of visual sensitivity and decisional aspects of subjects' performance. Evidence for specificity in the development of sensory versus decisional process tolerance to intoxication effects was found. The major result was that each subject made large and statistically reliable shifts in decisional criteria during the time course of the blood alcohol curve within alcohol testing sessions, even when visual sensitivity had adapted to alcohol intake effects. The results of this study illustrate the utility of tracing acute intake effects over repeated occasions of intoxication, and empirically testing subjects' assumed decisional strategies when modeling these effects.