0111 Effects of Sleep on Working Memory

Abstract

Abstract Introduction Improvements in working memory (WM) are associated with increased vagal autonomic activity during sleep. Sex hormones, which fluctuate across a menstrual cycle, influence sleep, autonomic activity, and cognitive performance. Given this complex interaction, we examined whether the relation between WM improvement and autonomic activity across a night of sleep was modulated by menstrual phase. Methods Twenty-five healthy female participants with natural, regular menstrual cycles (age = 28.14 ± 4.41 years) were enrolled. We employed a within-subject design to investigate the role of menstrual phase on autonomic activity and sleep-dependent working memory improvement. All participants completed two in-lab visits, with one visit during their low hormones phase (LH: 0 to +2 days from the start of menses) and one visit during their high hormone phase (HH: +1 to +4 days from the start of ovulation). We measured WM with the Operation-Span Task at 9PM and 8AM. Participants’ overnight sleep was monitored with EEG and ECG. We measured parasympathetic activity using the high-frequency heart rate variability (hfHRV) and the root-mean-square of successive differences between normal heartbeats (RMSSD). We used linear-mixed effect models and Pearson’s r. Results No differences in WM were found between menstrual phases (all ps > .223). Interestingly, however, HRV during NREM positively correlated with WM improvement in LH (hfHRV: r = .329, p = .093; RMSSD: r = .327, p = .096), but not during HH (hfHRV: r = -.197, p = .355; RMSSD: r = -.179, p = .402). The differences between correlations were significant (hfHRV: p = .038; RMSSD: p = .045). Conclusion Prior meta-analysis revealed greater vagal autonomic activity during LH (menses), compared with other phases. Though we didn’t replicate this finding, we did show a significantly stronger relation between vagal autonomic activity and overnight WM improvement during this low hormone phase. Our results suggest that menstrual phase shifts the reliance of sleep-dependent WM improvement to vagal autonomic mechanisms. Support (If Any) UCI MIND/WAM 02-2020