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Abstract
Memory consolidation is a critical process by which labile learning is stabilized for long-term retention. While a growing body of research supports the role of sleep in consolidating memory, much of this work has focused on rote learning and overnight sleep. Less is known about whether generalized learning — where learners extract abstract patterns that can transfer across novel contexts — also benefits from shorter sleep opportunities, such as naps. Moreover, the mechanisms by which sleep supports such generalization remain unclear. In a series of behavioral and polysomnographic experiments, participants were trained to recognize synthetic speech stimuli in which no words were repeated. These tasks required learners to generalize beyond memorized items and instead acquire abstract acoustic-phonetic patterns. Chapter 2 asks whether a 90-minute nap is sufficient to stabilize generalized learning, compared to remaining awake. These findings suggest that a single nap can consolidate generalized learning, mimicking effects of overnight sleep. Chapter 3 replicates these behavioral findings using a revised design and confirms that participants show performance recovery after a nap. Importantly, this chapter introduces EEG measures and shows that the presence of the EEG cap does not disrupt consolidation. Chapter 4 investigates whether sleep history prior to the nap influences the effectiveness of sleep-based consolidation. Results reveal that recent and cumulative sleep restriction are associated with altered sleep architecture during the nap, and that waking out of slow wave sleep is associated with higher recovery post nap. This suggests that an individual’s sleep history can modulate how effectively sleep consolidates learning. Chapter 5 uses polysomnography to examine which features of nap sleep predict individual differences in memory recovery. Contrary to predictions from some consolidation theories, sleep spindle density was not significantly associated with recovery. Instead, both slow wave sleep (SWS) and REM sleep duration were positively associated with improved post-nap performance, as long as both stages were present during the nap. These findings highlight the importance of both sleep stages and suggest that intact sleep cycles may be necessary to support consolidation of generalized perceptual learning. Together, this work challenges the notion that multiple sleep cycles are required for consolidation, extends our understanding of generalized learning, and underscores the role of both sleep history and specific sleep stages — particularly SWS and REM — in supporting memory stabilization.