Reversal learning tasks are commonly used to test cognitive flexibility by
allowing humans and experimental animals to learn one set of rules to gain
rewards and then respond to changes in those rules. In this experiment,
male and female Long-Evans rats were trained to discriminate distinct
visual stimuli associated with different reward probabilities (a
2-alternative choice), requiring them to nosepoke the stimuli on a
touchscreen. A range of reward likelihoods from probabilistic (i.e., 90:30,
90:10, 70:30) to deterministic (100:0) were administered. We explored how
sex may affect performance on the following measures: probability correct
(learning), latencies to nosepoke correct/incorrect stimuli (decision
processing speed), trial initiation (attention), and reward collection
(motivation). Across separate cohorts of rats, we found differences during
the reversal phase mainly centered on decision processing speed, with
females performing more slowly than males with longer initiation latencies.
Attention measures (trial initiation) were also attenuated in females
compared to males in both discrimination and reversal learning. Males
failed to initiate more trials in 70:30 discrimination learning than in
90:30. [KD1] Importantly, overall learning (probability of correct choice
and rewards received per session) did not differ by sex, suggesting all
animals learned equivalently despite performance drawbacks. Our results
provide some of the first fine-grained evidence for sex differences in
stimulus-based reversal learning. Ongoing experiments are aimed at testing
animals on more certain 90:10 and 100:0 reward probabilities. We predict
there will be less pronounced sex differences on attention and processing
speed as reward probability increases.