RG 5434: Information Abstraction During Sleep

Sleep is not an idle state. Instead, the organism continues to process information that has been encoded during prior wakefulness. During waking, the organism takes up huge amounts of information, much more than can be kept for the long term. We assume that information processing in the “off-line” condition of sleep serves to reduce this information load by abstracting “gist” information, with only this gist information becoming stored in long-term memory. Gist might represent invariant information repeating across experiences or salient information, e.g., a danger signal, that is unique to a specific experience. The main goals of the planned Research Unit are to characterize what the gist is that is stored for the long-term, and how it is abstracted during sleep. We address these questions in the framework of the “active systems consolidation” concept of sleep-dependent memory processing, assuming that consolidation processes during sleep specifically pertain to the hippocampus-dependent episodic memory system. In this concept, information abstraction during sleep is considered a consequence of the gradual redistribution of representations from hippocampal to primarily neocortical networks serving as long-term stores. Mechanisms underlying active systems consolidation shall be investigated, together with behavioral indicators of memory, at the level of large-scale network activity and oscillations (by fMRI, EEG, local field potential recordings, wide-field fluorescence microscopy) as well as at the level of microcircuits and single cells (by single unit recordings and two-photon imaging). For our ultimate aim to establish active systems consolidation of abstracted gist memory as a fundamental function of sleep, we will characterize the consolidation process in the sleeping brain for widely different (social and non-social) stimulus domains, and identify ontogenetic and phylogenetic regularities in this process. Understanding the memory function of sleep shall pave the way for translational approaches to ameliorate diseases in clinical settings and to enhance cognitive capabilities in educational settings.