Bidirectional modulation of spatial working memory by ethanol

Background: It is common knowledge that ethanol causes cognitive and memory impairments. Although these deficits are attributed to its central depressant properties, ethanol has biphasic effects and at low doses can produce excitatory actions. Methods: Here we examined whether ethanol could have biphasic effects on performance in a delayed alternation task in a T-maze, a behavioral test of working memory. Results: A dose-response study showed that intermediate doses of ethanol (1 g/kg) were associated with impairments of working memory in rats, as assessed at short intertrial intervals (10 sec). In contrast, at longer delays (120 sec), when the delayed alternation performance was reduced markedly in controls, a lower dose of ethanol (0.5 g/kg) significantly improved working memory. Conclusions: These results demonstrate a dose-dependent, bidirectional effect of ethanol on working memory and implicate the prefrontal cortex, the site of working memory function, as a target of ethanol action. The cognitive improvements caused by low, excitatory doses of ethanol may be perceived as rewarding and could have relevance for chronic ethanol consumption in humans.