The Effects of Direct Context Reactivation During Sleep on Memory

The context in which memories are encoded is a major factor influencing how memories are organized. Individual memories are bound to the context (e.g., the location, time and state of mind in which they are encoded) and this context is later reinstated to recall the details related to the memory. Although the role of context has been explored with regard to memory encoding and retrieval, its role during sleep-related memory consolidation has not been explored. Memories are thought to be reactivated during sleep, subsequently benefitting from the process. This study will use encephalography (EEG) in humans to consider several competing hypotheses regarding context's role in sleep reactivation, thereby enhancing the current understanding of how reactivation of memory over sleep relates to models of context and memory. Participants will learn to associate pictures of scenes to different sounds and to smaller images of items and animals, and then learn the spatial locations of these smaller images on a grid. Crucially, for half of these scenes, the sounds themselves will then also be linked directly to some of images during training. The associated sounds will then be unobtrusively presented during sleep, in a manner that has been shown to improve associated memories. The subsequent memory benefits will reveal whether (1) all images associated with the cued scene will benefit from cuing, demonstrating a context-reactivation effect; (2) only the images directly associated with presented sound will benefit from the cuing, demonstrating a item-reactivation effect; or (3) some composite of these two models. Regardless of which hypothesis is correct, the results will expand our current understanding regarding the role context plays in sleep consolidation.