Reward benefits to memory formation have been robustly linked to dopaminergic activity. Despite established characterization of dopaminergic mechanisms as operating at multiple timescales, potentially supporting distinct functional outcomes, the temporal dynamics by which reward might modulate memory encoding are just beginning to be investigated. In the present study, we leveraged a mixed block/event experimental design to disentangle transient and sustained reward influences on task engagement and subsequent recognition memory in an adapted monetary-incentive encoding (MIE) paradigm. Across three behavioral experiments, transient and sustained reward modulation of item and context memory was probed, at both 24-hour and ~10-minute retention intervals, to investigate the importance of overnight consolidation. In general, we observed that transient reward was associated with enhanced item memory encoding, while sustained reward modulated task engagement at encoding (specifically, increasing response speed) but did not confer a benefit to subsequent memory performance. Notably, reward benefits to item memory performance were somewhat inconsistent across the three experiments, and in contrast to predictions, we did not observe reward modulation of context memory performance or amplification of reward effects by overnight consolidation. Taken together, the observed pattern of behavior suggests potentially distinct roles for transient and sustained reward in memory encoding and cognitive performance and suggests that further investigation of the temporal dynamics of dopaminergic contributions to memory formation will advance understanding of motivated memory.
A selective benefit of transient, but not sustained, reward to memory formation
