Sensitivity to outcome devaluation in operant tasks is better predicted by food restriction level than reinforcement training schedule in mice

Abstract

Behavioral strategies are often classified based on whether reinforcement is controlled by the value of the reinforcer. Value-sensitive behaviors, in which animals update their actions when reinforcer value is changed, are classified as goal-directed; conversely, value-insensitive actions, where behavior remains consistent when the reinforcer is removed or devalued, are considered habitual. Understanding the features of operant training that bias behavioral control toward either strategy is essential to understanding the cognitive and neuronal processes on which they rely. Using basic reinforcement principles, behavior can be biased toward relying on either process: random ratio (RR) schedules are thought to promote the formation of goal-directed behaviors while random intervals (RI) promote habitual control. However, how the schedule-specific features of these task structures relate to external factors to influence behavior is not well understood. Using male and female mice on distinct food restriction levels, we trained each group on RR schedules with responses-per-reinforcer rates matched to their RI counterparts to control for differences in reinforcement rate. We determined that food restriction level has a stronger effect on the behavior of mice following RR schedules than mice following RI schedules and that food restriction better predicted sensitivity to outcome devaluation than training schedule. Our results support the idea the relationships between RR or RI schedules with goal-directed or habitual behaviors, respectively, are more nuanced than previously appreciated and suggest that an animals engagement in a task must be accounted for, together with the structure of reinforcement schedules, to appropriately interpret the cognitive underpinnings of behavior. Significance statementUnderstanding the basic learning principles that control behavior is essential to developing therapies for psychiatric disorders such as addiction or obsessive-compulsive disorder. Reinforcement schedules are thought to control the reliance on habitual versus goal-directed control during adaptive behaviors. However, external factors that are independent of training schedule also influence behavior, for example by modulating motivation or energy balance. In this study, we find that food restriction levels are at least equally important as reinforcement schedules in shaping adaptive behavior. Our results add to the growing body of work showing the distinction between habitual and goal-directed control is nuanced.