Consolidation promotes rule discovery rather than semantic abstraction

A bioRxiv pre-print of my Master’s research is available here.

Abstract: Human memory for recent events is believed to undergo reactivation during sleep. This process is thought to be relevant for the consolidation of both individual episodic memories and gist extraction, the formation of generalized memory representations from multiple, related memories. Which kinds of gist are actually enhanced, however, is the subject of less consensus. To address this question, we focused our design on four types of gist: inferential gist (relations extracted across non-contiguous events), statistical learning (regularities extracted from a series), summary gist (a theme abstracted from a temporally contiguous series of items), and category gist (characterization of a stimulus at a higher level in the semantic hierarchy). Sixty-nine participants (30 men, 38 women, and 1 other) completed memory encoding tasks addressing these types of gist and corresponding retrieval tasks the same evening, the morning after, and one week later. Inferential gist and statistical learning were retained over a week, whereas memory for associative gist (category and summary gist) decayed. Higher proportions of REM and more spindles were associated with worse performance in a statistical learning task controlling for time and after one week, respectively. Our results suggest consolidation processes promote discovery of rules through synthesis of episodes (statistical learning and transitive inference), rather than semantic abstraction per se (category and summary gist). They further support the view that REM sleep is involved in schema disintegration, which works against participants’ ability to identify regularities within temporal series.