Schedule of Events | Symposia

Sketchpad Series

Investigating the impact of cognitive load on hippocampal activity and episodic memory

Poster Session C - Sunday, March 30, 2025, 5:00 – 7:00 pm EDT, Back Bay Ballroom/Republic Ballroom

Emma Laurent¹ (emmalaurent@g.harvard.edu), Elizabeth Miclau¹, Lila Davachi², Elizabeth Phelps¹; ¹Harvard University, ²Columbia University

Accumulating evidence highlights the role of hippocampal replay during sleep and wakeful rest in supporting memory consolidation. Additionally, post-encoding rest has been shown to enhance long-term memory compared to task engagement. These "offline" internally-oriented states are associated with increased activity in the Default Network (DN), which is implicated in retrieving past experiences and simulating future events. In contrast, the Dorsal Attention Network (DAN) is thought to allocate cognitive resources toward external stimuli and exhibits functional opposition to the DN. A plausible mechanism underlying the benefits of rest as compared to “online” task engagement is that the latter recruits the DAN, suppressing the DN and thereby its constituent hippocampus, which is critical for memory processing. Leveraging existing fMRI data, we find that hippocampal activity is systematically suppressed with increasing cognitive load. In a within-subjects fMRI study, we investigate whether this load-dependent suppression of hippocampal activity impairs memory consolidation. Participants completed a brief 0- or 2-back task following an incidental encoding task, with episodic memory subsequently assessed. This process was repeated for the remaining N-back condition. We hypothesize that increasing post-encoding cognitive load will lead to diminished memory performance, reflecting group-level reductions in BOLD activity in the DN. To test this, we will conduct an ROI analysis of two DN constituents: the hippocampus and vmPFC. Furthermore, we predict this effect will be mediated by individual differences in hippocampal suppression, as revealed by first-level contrasts. These findings aim to advance our understanding of the relationship between cognitive load, hippocampal function, and memory consolidation.

Topic Area: LONG-TERM MEMORY: Episodic