Effects of prolonged ethanol exposure on neurophysiological measures during an associative learning paradigm

Long-term ethanol exposure has been reported to produce electrophysiologica l and cognitive impairments in some alcoholics. This study assessed the eff ects of chronic ethanol exposure on neurophysiological indices of associati ve learning in rats. Male Wistar rats (46) were exposed to ethanol vapor (E tOH group) or air (control group) for 6 consecutive weeks. After the animal s were withdrawn from ethanol, electrodes were implanted in the frontal and parietal cortices and in the amygdala. Following a prolonged abstinence fr om ethanol (10-15 weeks), rats were exposed to a classical conditioning par adigm in which a food pellet was paired with the presentation of an auditor y stimulus. During the first five sessions (conditioning phase), food pelle t presentation was paired with the presentation of an infrequently presente d tone. During the second five sessions (extinction phase), the association between food pellet presentation and the infrequently presented tone was w eakened by no longer presenting food pellets following the infrequent tone. During selected test sessions, event-related brain potentials (ERPs) elici ted by each tone (i.e. food-paired tone, non-paired tone) were recorded and analyzed. These analyses revealed differences in ERP responses between the groups. The latency of the N1 and P2 ERP components in the cortex of the c ontrol group, but not the EtOH group, increased during sessions when the as sociation between food pellet delivery and tone presentation was being esta blished or extinguished. These data support the hypothesis that chronic eth anol treatment results in a loss of responsivity in ERP components sensitiv e to changes in food-tone associations, even following a prolonged period o f withdrawal from ethanol. (C) 2000 Elsevier Science Ireland Ltd. All right s reserved.