The role of sleep in consolidation of multi-item bound representations

A wealth of literature has demonstrated that in terms of memory representations, items are not encoded equally. In part this has been suggested to be affected by conceptual knowledge, with items with pre-existing conceptual knowledge easier to encode and thus, more salient in subsequent representations. However, it is not known how this may affect different item modalities such as actions, objects, people, and locations. As such, this thesis seeks to understand the factors that can affect the different item modalities in multi-item memory representations primarily focusing on the role of sleep, which has been demonstrated to be beneficial for memory consolidation. In paper 1 the role of culture (Western v East Asian) was examined in differences in bound memory representations, focusing on object-scene and action-scene pairings. It was observed that culture was not a factor for actionscene pairings but Western participants were significantly more accurate than East Asian participants for object-scene pairings. Furthermore, object-scene recognition was significantly more accurate than action-scene recognition across both cultures, suggesting a difference between actions and objects in ease of recognition. In paper 2 this was expanded to see the role of sleep in consolidation of action-scene/object-scene pairings. As with paper 1 object-scene pairings were significantly more accurate than action-scene pairings in immediate testing, and object-scene recognition experienced a benefit of sleep, with accuracy higher in the sleep group than the wake group. This difference was not replicated in the action-scene task. Paper 3 sought to apply the previous results to a practical situation, that of eyewitness testimony as the existing literature has revealed that within eyewitness testimony participants are susceptible to errors of binding at retrieval. Across the two sessions we observed a significant difference in item modality, with action details recalled to a higher level than object, location, and people details but there was no effect of sleep/wake. Paper 4 moved away from visual memory and instead focused on the role of sleep on conceptual knowledge using the DRM paradigm. Participants were trained on 12 DRM wordlists and then were assigned either to a short-term wake group or a nap group monitored with polysomnography. At retrieval, sleep significantly increased lure-unseen acceptance compared to the equivalent period of wake, providing evidence of sleep promoting false memory generation. Furthermore, RH spindle generation relative to LH spindle generation was significantly correlated with false recognition of lure-unseen words, suggesting a central role of the RH in false memory generation.