Dopamine is thought to provide reward prediction error signals to temporal lobe memory systems, but the role of these signals in episodic memory has not been fully characterized. Here we developed an incidental memory paradigm to (i) estimate the influence of reward prediction errors on the formation of episodic memories, (ii) dissociate this influence from surprise and uncertainty, (iii) characterize the role of temporal correspondence between prediction error and memoranda presentation and (iv) determine the extent to which this influence is dependent on memory consolidation. We found that people encoded incidental memoranda more strongly when they gambled for potential rewards. Moreover, the degree to which gambling 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 24 h, indicating that it is not dependent on memory consolidation. These results suggest a computationally and temporally specific role for reward prediction error signalling in memory formation.
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The behavioural data from both experiments are available from the corresponding author on request.
Custom code used to analyse and model the data is available from the corresponding author on request.
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We thank A. Collins for comments on the experimental design and thank J. Helmers and D. Rogers for their help in setting up and collecting data through Amazon Mechanical Turk. This work was funded by NIH grant numbers F32MH102009 and K99AG054732 (M.R.N.), NIMH R01 MH080066-01 and NSF Proposal number 1460604 (M.J.F.), and R00MH094438 (D.G.D.). The funders had no role in study design, data collection and analysis, decision to publish or preparation of the manuscript.
The authors declare no competing interests.
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Jang, A.I., Nassar, M.R., Dillon, D.G. et al. Positive reward prediction errors during decision-making strengthen memory encoding. Nat Hum Behav 3, 719–732 (2019). https://doi.org/10.1038/s41562-019-0597-3