Systematic cognitive load and its influence on episodic memory

Poster Session B - Sunday, April 14, 2024, 8:00 – 10:00 am EDT, Sheraton Hall ABC

Emma Laurent¹ (emmalaurent@g.harvard.edu), Linda de Voogd², Lila Davachi³, Elizabeth Phelps¹; ¹Harvard University, ²Universiteit Leiden, ³Columbia University

Accumulating evidence suggests that hippocampal replay during sleep and rest supports memory consolidation. Recent research indicates that post-encoding rest benefits long-term memory more than task engagement. These "offline" states involve increased activity in the Default Network (DN), known for its role in both retrieving past experiences and simulating future events. The DN exhibits functional opposition with the Dorsal Attention Network (DAN), hypothesized to direct cognitive resources towards external stimuli. A plausible explanation for this phenomenon suggests that active task engagement via DAN might suppress DN, including the hippocampus, a critical component of memory processing. Consistent with this claim, we find that hippocampal activity systematically decreases with increasing cognitive load using existing data from various N-back levels. We then investigate whether this reduction in hippocampal activity impairs memory consolidation. Participants completed a brief N-back task or rested after an incidental encoding task, with memory assessed immediately and one day later. Our results support the idea that higher post-encoding cognitive load disrupts memory processes. The rest group, however, showed no advantage over task groups. Preliminary results suggest that self-reported thoughts during rest relate to individual memory performance: thinking about the encoding task improved memory, while unrelated thoughts had a detrimental effect. These findings highlight the intricate relationship between cognitive load, rest, and memory consolidation, emphasizing the role of post-encoding cognitive states in shaping memory outcomes. Furthermore, they underscore that rest is not invariably passive, as spontaneous thought processes may engage working memory systems or tax memory retrieval, moderating consolidation in complex ways.

Topic Area: LONG-TERM MEMORY: Episodic