Cost-benefit Tradeoff Mediates the Rule- to Memory-based Transition during Practice.

Practice not only improves task performance, but also changes task execution from rule- to memory-based processing by incorporating experiences from practice. We tested the hypothesis that strategy transition in task learning results from a cost-benefit analysis of candidate strategies. Participants learned two task sequences and were then queried the task type at a cued sequence and position. Behavioral improvement with practice can be accounted for by a computational model implementing cost-benefit analysis. Model-guided fMRI analysis shows frontal and parietal activations scaling with the demand of executing rule and memory strategy, respectively. fMRI activation pattern analysis further reveals widespread strategy-specific neural representations when their corresponding strategy is executed. Lastly, strategy transition is related to neural representation change in the dorsolateral prefrontal cortex and pattern separation in the ventromedial prefrontal cortex and the hippocampus. These findings shed light on how practice optimizes task performance by shifting task representations at the strategy level.