Sleep Benefits Procedural Motor Learning in Older Adults With Additional Practice

Aging is associated with declines in both memory performance and sleep quality, raising questions about their potential connections. While younger adults consistently show sleep-dependent memory consolidation (SDC) benefits for procedural motor learning, findings in older adults have been inconsistent. The present study investigated whether additional training could enhance SDC in older adults, thereby mitigating age-related deficits in procedural motor memory consolidation. Young adults (18-24 years) and older adults (62-75 years) were assigned to standard training or overtraining conditions before completing an explicit serial reaction time task before and after a 12-hour interval of either wakefulness or sleep. Polysomnography was used to assess sleep architecture, including spindles and slow oscillation-spindle coupling, key neural mechanisms implicated in SDC. Behavioral results demonstrated significant SDC in young adults but not in standard-trained older adults, replicating prior research. However, overtrained older adults exhibited a significant sleep-related benefit in performance, supporting the hypothesis that additional training enhances encoding strength and facilitates consolidation. Additional analysis indicated that, once older adults’ encoding strength was sufficient to elicit sleep-dependent consolidation, weaker memories may be preferentially enhanced by sleep. Despite these behavioral improvements, sleep physiology did not differ between standard-trained and overtrained older adults, and sleep microstructure analyses revealed largely inconclusive associations between overnight performance changes and spindle activity or slow oscillation-spindle phase-amplitude coupling. Contrary to expectations, young adults showed weaker coupling during NREM2, and stronger coupling did not predict greater SDC in either age group. These findings suggest that encoding strength plays a critical role in determining sleep’s impact on procedural memory consolidation. Future research should further examine the interaction between pre-sleep encoding and sleep physiology to better understand the mechanisms underlying SDC for procedural memory in aging populations.