0062 Slow Oscillatory Transcranial Direct Current Stimulation During Restricted Nighttime Sleep Enhances Memory Consolidation

• Published in: Sleep (New York, N.Y.) Vol. 46; no. Supplement_1; p. A29
• Main Authors: Riedy, Samantha, Doty, Tracy Jill, Balkin, Thomas, Stekl, Emily, Alger, Sara, Hughes, John
• Format: Journal Article
• Language: English
• Published: 29.05.2023
• ISSN: 0161-8105; 1550-9109
• DOI: 10.1093/sleep/zsad077.0062

Abstract Introduction Slow oscillatory transcranial direct current stimulation (SO-tDCS) during the first 30 min of nighttime sleep has been shown to improve memory consolidation of word pairs encoded immediately prior to sleep onset. We examined whether SO-tDCS administered during the second half of a restricted nighttime sleep opportunity likewise improves memory consolidation for previously encoded word pairs and mitigates subsequent performance deficits. Methods After three nights of baseline sleep in the laboratory, healthy subjects (ages 18-33, n=27, 17 females) were administered SO-tDCS (N=12) or SHAM (N=15) during the second hour of a 2h sleep period (between the hours of 23:00 and 03:00). Prior to this 2h sleep period, subjects were presented a series of 55 word-pairs. They were asked to recall 46 of the pairs immediately after learning (T0), and again at 20 min (T20) and 120 min (T120) post-awakening. Number of pairs recalled at T20 and T120 relative to T0 were analyzed with a mixed-effects ANOVA. Negative values indicate that subjects forgot pairs post-awakening relative to the initial learning recall. Results Subjects correctly recalled 35.0 ± 9.2 words (mean ± SD) at T0. Relative to T0, subjects in the SHAM condition correctly recalled significantly fewer words post-awakening than those in the SO-tDCS condition (SHAM: -0.8 ± 1.6 words; SO-tDCS: 0.3 ± 1.3 words; F=6.20, p=0.02), and fewer words at T20 than T120 (T20: -0.6 ± 1.5 words; T120: -0.1 ± 1.6 words; F=4.67, p=0.04). On average, subjects in the SHAM condition forgot words upon awakening relative to T0 (T20: -1.0 ± 1.4; T120: -0.6 ± 1.7 words), while those in the SO-tDCS condition forgot few to no words at T20 (0.0 ± 1.5 words) and actually recalled more words at T120 than T0 (0.6 ± 1.1 words). Conclusion Participants in the SHAM condition recalled fewer words after the restricted sleep period, whereas those in the SO-tDCS group increased recall following 2h of sleep. The present findings have important implications for the development of fatigue mitigation strategies during military operations, when sustaining performance in the face of insufficient sleep is critical. Support (if any) Department of Defense Military Operational Medicine Research Program (MOMRP)