Year: 2026
Type: dissertation
Abstract: Autobiographical memories change over the course of consolidation, allowing us to both re-experience specific events in vivid detail and to summarize across years of our lives. One aspect of memory transformation is thought to be a change in the relationship between a memory and its encoding context. Several theories have proposed that sleep and dreaming may decontextualize memories to allow for the extrapolation of memories to novel contexts, but this feature has not yet been examined in autobiographical memories. One possible mechanism for memory decontextualization during sleep may be a transformation of the memory trace in the hippocampus. In Chapter 2, across two pre-registered experiments, I demonstrated that, phenomenologically, remote autobiographical memories were more spatially contextualized than recent memories. Remote memories were also reported at a wider spatial scale. In Chapter 3, I investigated how a single night of sleep and dreaming was associated with real-life everyday event memories across a variety of features, including contextualization. I found that sleep promoted phenomenological decontextualization. Furthermore, when testing the same memories over a one-year delay, I replicated the finding from Chapter 2 that memories become more contextualized over time. Together, the findings from Chapters 2 and 3 suggest that spatial context dependency changes non-linearly in autobiographical memories, such that memories become decontextualized with a single night of sleep, but over longer delays, memories become more closely bound to their context. Finally, it is well established that whether a memory retains contextual details is tied to the functioning of the hippocampus. However, little is known about the role of sleep in those with damage to the hippocampal system. In Chapter 4, I describe a unique case of sleep-related amnesia. I found that sleep impaired newly-formed naturalistic memories in CT, a young woman with damage to her right fornix and an intact hippocampus, suggesting that the integrity of the hippocampal system is necessary for memory consolidation during sleep. Together, these studies demonstrate that the first night of sleep transforms autobiographical memories, a process that requires the integrity of the hippocampal system, and that the relationship between a memory and its spatial context follows a non-linear trajectory.
Source: TSpace (University of Toronto)
Author: Matorina, Nelly
Language: English
Subfield: Cognitive Neuroscience
Field: Neuroscience
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W7203961402