When making decisions, we are often forced to choose between something safe we have chosen before, and something unknown to us that is inherently risky, but may provide a better long-term outcome. This problem is known as the Exploitation-Exploration (EE) Trade-Off. Most previous studies on the EE Trade-Off have relied on response data, leading to some ambiguity over whether uncertainty leads to true exploratory behavior, or whether the pattern of responding simply reflects a simpler ratio choice rule (such as the Generalized Matching Law (Baum, 1974; Herrnstein, 1961)). Here, we argue that the study of this issue can be enriched by measuring changes in attention (via eye-gaze), with the potential to disambiguate these two accounts. We find that when moving from certainty into uncertainty, the overall level of attention to stimuli in the task increases; a finding we argue is outside of the scope of ratio choice rules.

Background

Forced alcohol (ethanol, EtOH) exposure has been shown to cause significant impairments on reversal learning, a widely-used assay of cognitive flexibility, specifically on fully-predictive, deterministic versions of this task. However, previous studies have not adequately considered voluntary EtOH consumption and sex effects on probabilistic reversal learning. The present study aimed to fill this gap in the literature.

Methods

Male and female Long-Evans rats underwent either 10 weeks of voluntary intermittent 20% EtOH access or water only (H2O) access. Rats were then pretrained to initiate trials and learn stimulus-reward associations via touchscreen response, and subsequently required to select between two visual stimuli, rewarded with probability 0.70 or 0.30. In the final phase, reinforcement contingencies were reversed.

Results

We found significant sex differences on several EtOH-drinking variables, with females reaching a higher maximum EtOH consumption, exhibiting more high-drinking days, and escalating their EtOH at a quicker rate compared to males. During early abstinence, EtOH drinkers (and particularly EtOH-drinking females) made more initiation omissions and were slower to initiate trials than H2O drinking controls, especially during pretraining. A similar pattern in trial initiations was also observed in discrimination, but not in reversal learning. EtOH drinking rats were unaffected in their reward collection and stimulus response times, indicating intact motivation and motor responding. Although there were sex differences in discrimination and reversal phases, performance improved over time. We also observed sex-independent drinking group differences in win-stay and lose-shift strategies specific to the reversal phase.

Conclusions

Females exhibit increased vulnerability to EtOH effects in early learning: there were sex-dependent EtOH effects on attentional measures during pretraining and discrimination phases. We also found sex-independent EtOH effects on exploration strategies during reversal. Future studies should aim to uncover the neural mechanisms for changes in attention and exploration in both acute and prolonged EtOH withdrawal.