UC Irvine

Sleep plays a critical role in the improvement of both episodic memory and working memory, with non-rapid eye movement neural oscillations, including slow oscillations (0.5-1Hz, SO) and sleep spindles (12-15Hz), causally implicated in these processes. However, studies elucidating the precise mechanisms underlying these processes are needed. Specifically, it remains unclear how neural oscillations during sleep coordinate with functional changes in the brain to facilitate the maintenance of information-specific episodic memories, or the increases in information-general working memory.The present dissertation aims to address these gaps in knowledge by investigating the neural mechanism underlying sleep-dependent episodic memory consolidation and working memory improvement. In study 1, I investigate how sleep protects episodic memory against waking interference. I ask whether sleep protects memory against future interference or if it rescues memory after interference has already occurred. In study 2, I probe the role of sleep spindles underlying sleep-dependent episodic memory consolidation. Specifically, I present a placebo-controlled, double-blind study that pharmacologically enhances sleep spindles to establish a causal role of sleep spindles and their temporal coupling with SOs in episodic memory consolidation. In study 3, I employ simultaneous EEG-fMRI to examine the neural activities associated with working memory as well as subsequent sleep, with a specific focus on SO as it’s a shared resource for both episodic and working memory. Together, these studies lead to a theoretical model of how the same sleep event may facilitate improvements across multiple cognitive domains. Specifically, SOs and it’s temporal coupling with sleep spindles coordinate with functional changes in specific memory networks to facilitate performance.