A novel multidimensional reinforcement task in mice elucidates sex-specific behavioral strategies

Background: Sex is a critical biological variable in the neuropathology of psychiatric disease, and in many cases, women represent a vulnerable population. It has been hypothesized that sex differences in neuropsychiatric disorders are manifestations of differences in basic reward processing. However, preclinical models often present rewards in isolation, ignoring that ethologically, reward seeking requires the consideration of potential aversive outcomes. Methods: We developed a Multidimensional Cue Outcome Action Task (MCOAT) to dissociate motivated action from cue learning and valence. Mice are trained in a series of operant tasks. In phase 1, mice acquire positive and negative reinforcement in the presence of discrete discriminative stimuli. In phase 2, both discriminative stimuli are presented concurrently allowing us to parse innate behavioral strategies based on reward seeking and shock avoidance. Phase 3 is punished responding where a discriminative stimulus predicts that nose-poking for sucrose occurs concurrently with footshock, allowing for the assessment of how positive and negative outcomes are relatively valued. Results: Females prioritize avoidance of negative outcomes over seeking positive, while males have the opposite strategy. In cases where rules are uncertain, males and females employ different strategies, with females demonstrating bias for shock avoidance. Conclusions: The MCOAT has broad utility for neuroscience research where pairing this task with recording and manipulation techniques will allow for the definition of the discrete information encoded within cellular populations. Ultimately, we show that making conclusions from unidimensional data leads to inaccurate generalizations about sex-specific behaviors that do not accurately represent ground truth.