Changes induced in the representation of learned sequences due to memory consolidation

Abstract

Studies of sequence learning have documented memory consolidation, in which post-learning sleep facilitates the retrieval of items from a succeeding chunk while retrieving items from a prior chunk. However, it remains unclear what changes in the representation of a learned sequence are induced by sleep. We investigate whether post-learning sleep strengthens the connections between chunks or between individual items within a sequence. After learning a sequence as two separate chunks, participants retrieved the middle part of the sequence, consisting of the second half of the first chunk and the first half of the second chunk, either as an isolated sequence or as part of the complete learned sequence. The results show that sleep improved retrieval of the middle part only in the complete sequence condition, suggesting that sleep strengthens the connections between chunks, rather than between items, and that the chunk structure is retained after memory consolidation.