States of rest and sleep are critical for optimal human cognitive function. Even during sleep, when sensory input and conscious awareness are minimal, the brain continues to process information from the previous day. Research in animals demonstrates that patterns of neural activity first seen during waking exploration of an environment are later "reactivated" during quiet rest and sleep. In humans, sleep consolidates and enhances previously formed memories. In parallel with this sleep-dependent memory processing, memories of recent experiences contribute to the images, thoughts, and narratives that we commonly call "dreams". Thought to be a critical component of long-term memory formation, post-learning reactivation of memories in humans has not been adequately studied, and is still poorly understood. The research proposed here would provide the first EEG-based characterization of offline memory reactivation in humans, analyzing global spatial patterns of the EEG signal recorded during encoding of a virtual navigation task, and during post-training rest and sleep. In parallel, the sampling of ongoing subjective experience provides a measure of memory reactivation at the cognitive level. Using the technique of "microstate analysis", our preliminary findings suggest that learning- related EEG patterns reappear during subsequent sleep, and that the extent of this "reactivation" predicts post- sleep task improvement. If successful, the proposed research would confirm that offline reactivation underlies memory consolidation in humans, as expressed in both electrophysiological and cognitive measures. In its focus on describing memory consolidation across multiple levels of analysis (integrating measures of behavior, electrophysiology, and conscious experience), this project is strongly in line with the proposed "sleep/wake construct" in NIMH's new Research Domain Criteria initiative (RDoC).
The integration of new learning into long-term memory storage is thought to involve the reactivation of memories during periods of quiet wakefulness and sleep. This research offers a novel approach to characterizing the brain-basis of these processes in humans, with the potential to facilitate a greater understanding of long-term memory formation and consolidation in wake and sleep, as well as their dysfunction in memory- and sleep-related disorders.
|Wamsley, Erin J (2014) Dreaming and offline memory consolidation. Curr Neurol Neurosci Rep 14:433|