Sleep Variability Related to Reduced Neural Distinctiveness for Episodic Memory Encoding: An fMRI Study Across the Adult Lifespan

Poster Session B - Sunday, March 30, 2025, 8:00 – 10:00 am EDT, Back Bay Ballroom/Republic Ballroom

Kyoungeun Lee¹ (klee773@utexas.edu), Audrey Duarte¹, Thackery Brown²; ¹UT Austin, ²Georgia Tech

Sleep is a critical lifestyle factor associated with episodic memory. While prior research has largely examined effects of acute sleep deprivation in younger adults, less is known about how habitual sleep quality, including night-to-night variability, impacts episodic memory and supporting neural activity across the adult lifespan. In this study, we investigated how sleep variability relates to the neural differentiation supporting successful episodic memory encoding, and whether this relationship differs with age. Participants aged 18 to 79 were scanned as they encoded emotional and neutral pictures. They performed an old/new recognition task one week later. Habitual sleep was monitored during this interval using actigraphy to quantify the variability of sleep duration. Representational Similarity Analysis (RSA) was applied to the fMRI data to assess neural differentiation between subsequently remembered and forgotten events, serving as a neural index of successful encoding. We hypothesized that greater neural distinctiveness (hits vs. misses) would be associated with better episodic memory performance. In addition, we predicted that greater sleep variability may hinder successful encoding, leading to reduced neural distinctiveness. Consistent with our predictions, we found that more distinctive neural representations (hits vs. misses) were associated with better memory performance, across stimulus valence and age. Furthermore, individuals with greater sleep variability showed reduced memory-specific neural representations, particularly in younger age. This suggests that inconsistent sleep duration may be negatively related to the neural mechanisms supporting episodic memory, especially in early adulthood. These findings highlight the importance of establishing stable sleep habits for cognitive health from early adulthood.

Topic Area: LONG-TERM MEMORY: Development & aging