The Constructive Role of Spatial Context in Event Memory

Episodic memory and spatial memory are two types of memory that have long been associated with the hippocampus, but the mechanism underlying their joint reliance on the hippocampus is debated. Some have proposed that mentally constructing scenes underlies episodic memory, serving as the foundation for remembered and imagined events. In this dissertation, I present four experimental studies testing questions relating to how spatial context affects, and may underlie, episodic memory, in terms of brain and behaviour. Chapter 2 describes a study in which more familiar contexts elicited more detailed and vivid memories of both scenes and events in young and older adults. The effect of context was comparable across age groups, despite the expected memory decline in older adults, suggesting that spatial context has a pervasive effect on episodic memory throughout the lifespan. Chapter 3 presents a study in which we found that participants spontaneously assigned spatial contexts to events where none was specified, suggesting that it is very difficult to vividly imagine and remember an episode devoid of spatial context. In Chapter 4, we found that individuals with memory loss relating to medial temporal lobe damage showed parallel impairments in memory for scenes and episodes, while retaining preserved schematic spatial memory. In a case of more posterior temporal/parietal damage, we found impairments in scene memory and more subtle deficits in episodic memory. These findings suggest that while the medial temporal lobe is crucial for both episodic and scene memory, other regions also contribute to scene memory and may serve as inputs to the hippocampal memory system. In Chapter 5, we examined the neural representation of imagined events using functional magnetic resonance imaging. Multivariate pattern analyses revealed that the largest network of neural areas represented information about the location of events, as compared to people or objects. These findings demonstrate how the location of an event plays a role in determining the neural representation of memories throughout networks associated with scene and event memory. Together, these studies demonstrate how spatial context affects the behavioural and neural characteristics of episodic memory and imagination, relating to theories of episodic memory and hippocampal function.Ph.D