Positive reward prediction errors during decision making strengthen memory encoding

Dopamine is thought to provide reward prediction errors signals to temporal lobe memory systems, but their role in episodic memory has not been fully characterized. We developed an incidental memory paradigm to 1) estimate the influence of reward prediction errors on formation of episodic memories, 2) dissociate this influence from surprise and uncertainty, 3) characterize the role of temporal correspondence between prediction error and memoranda presentation, and 4) determine the extent to which this influence is consolidation-dependent. We found that people encoded incidental memoranda more strongly when they gambled for potential rewards. Moreover, this strengthened encoding scaled with the reward prediction error experienced when memoranda were presented (and not before or after). This encoding enhancement was detectable within minutes and did not differ substantially after twenty-four hours, indicating that it is not consolidation-dependent. These results suggest a computationally and temporally specific role for reward prediction error signaling in memory formation.