Can neural correlates of encoding explain the context dependence of reward-enhanced memory?

Abstract

Selective encoding can be studied by manipulating how valuable it is for participants to remember specific stimuli, for instance by varying the monetary reward participants receive for recalling a particular stimulus in a subsequent memory test. It would be reasonable for participants to strategically attend more to high-reward items compared to low-reward items in mixed list contexts, but to attend both types of items equally in pure list contexts, where all items are of equal value. Reward-enhanced memory may be driven by automatic dopaminergic interactions between reward circuitry and the hippocampus and thus be insensitive to list context; or it may be driven by meta-cognitive strategies, and thus context-dependent. We contrasted these alternatives by manipulating list composition, and tracked selective encoding through multiple EEG measures of attention and rehearsal. Reward-enhanced memory depended on list composition: recall of high-reward items was increased in mixed, but not pure, lists. This result and aspects of the recall dynamics confirm predictions of the eCMR (emotional Context Maintenance and Retrieval) model. The power of steady-state visual evoked potentials was lower for high-reward items regardless of list composition, suggesting that high reward decreased visual processing of the stimuli and that ssVEPs may index the modulation of context-to-item associations predicted by eCMR. By contrast, reward modulated the amplitude of Late Positive Potential and Frontal Slow Wave only in mixed lists, mimicking the memory results. Taken together, the results provide evidence for the involvement of both automatic and strategic processes in how selective encoding shapes eventual memory.

The influence of emotion on temporal context models

“…Here we focused on predictions of TCMs, which have primarily examined interactions between emotion and temporal memory using the open-ended instructions of free recall, in which participants may recall items in any order they wish. As noted above, in mixed lists participants are more likely to transition between items of the same emotional arousal or valence (Horwath et al, 2023;Long et al, 2015;Talmi et al, 2019), yet participants exhibit the same level of temporal clustering between mixed lists and pure lists (Hellerstedt et al, 2023;Horwath et al, 2023). These findings underscore the maintenance of temporal information with changing stimulus features.…”

“…Like emotional items, items associated with high positive reward benefited from greater recall in mixed but not pure lists, and participants were more likely to initialize recall with a high reward item (Hellerstedt, Bekinschtein, & Talmi, 2023;Hellerstedt & Talmi, 2022;Horwath et al, 2023;Murphy et al, 2022;Siddiqui & Unsworth, 2011;Stefanidi et al, 2018;Talmi et al, 2021). Further replications of this finding also found that temporal contiguity did not vary between pure and mixed lists (Hellerstedt et al, 2023;Hellerstedt & Talmi, 2022;Horwath et al, 2023). The consistent temporal clustering reflects that all items are associated to temporal context to the same degree.…”

“…They assumed that positive reward evokes similar attentional processes as emotionally arousing items, and high versus low reward can be represented as two distinct source features, like negative versus neutral emotion (Le Pelley, Mitchell, Beesley, George, & Wills, 2016;Mather, Clewett, Sakaki, & Harley, 2016). Like emotional items, items associated with high positive reward benefited from greater recall in mixed but not pure lists, and participants were more likely to initialize recall with a high reward item (Hellerstedt, Bekinschtein, & Talmi, 2023;Hellerstedt & Talmi, 2022;Horwath et al, 2023;Murphy et al, 2022;Siddiqui & Unsworth, 2011;Stefanidi et al, 2018;Talmi et al, 2021). Further replications of this finding also found that temporal contiguity did not vary between pure and mixed lists (Hellerstedt et al, 2023;Hellerstedt & Talmi, 2022;Horwath et al, 2023).…”