Acquisition of tolerance to alcohol-induced memory deficits in humans

Abstract

The evidence on tolerance to the effects of alcohol on memory functions is conflicting. Comparisons of populations differing in drinking history (alcoholics versus normal subjects) provide clear evidence of tolerance to alcohol's effect in many indices of psychomotor performance, but not to impairment of recall by alcohol. In contrast, acute or intrasessional tolerance to alcohol's effect on memory has been demonstrated. In the context of a larger experiment on the acquisition of tolerance in nonalcoholic subjects an assessment of the effects of repeated daily exposure to alcohol on verbal recall was possible. The experimental design incorporated 3 baseline days prior to the administration of alcohol, 10 consecutive days of exposure to alcohol (1.0 g/kg test dose, with supplementary 0.9 g/kg after testing) and 3 further days on which no alcohol was administered. Data on seven subjects were available for the memory task, which consisted of free recall of lists of 24 words grouped into six categories of four words each. On each day, recall was assessed both prior to and following the administration of a control beverage or alcohol. Alcohol reduced the number of words recalled (P<0.005) and, with repeated exposure, the impairment of recall by alcohol was reduced (P<0.005) providing evidence of tolerance. The effect of alcohol and the development of tolerance were reflected primarily in the number of categories represented in recall, whereas the number of words recalled per category was relatively unaffected by alcohol. It was conjectured that previous failures to find tolerance to alcohol's effect on memory may reflect deficits in neuropsychologic functioning resulting from years of heavy drinking.