Mechanisms of Mapping Space in Human Memory
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1) We are interested in understanding the neural and cognitive events that give rise to episodic memory, and the factors that influence the efficacy of the declarative memory system in both health and disease. One such factor is psychological stress, which data suggest can disrupt relevant neural networks at various levels. Consequently, by altering memory function, stress from health, social, economic, and other challenges may have a significant impact on daily function. We are developing experiments to quantify how stress influences the detail with which memories are both formed and retrieved, and test predictions about how such changes relate to network-level mechanisms in the brain. One of our goals will be to expand the scope of this research from short-term impacts of stress to understanding how anxiety-related disorders and the long-term experience of stress affect both structure and function underlying memory and planning. 2) People vary widely in their memory and navigation abilities, but the neural bases for these individual differences are not well understood. We are interested in neural and cognitive traits that influence inherent processing abilities, as well as differences in processing strategies that impact memory and behavior. In keeping with a systems-level perspective of memory, considerable variance in individual abilities may relate to 1) structural and functional integrity within hippocampal subfield circuitry, which can impact the detail and discriminability of memories, and 2) network differences in how frontostriatal circuitry, along with parietal attention mechanisms, interacts with the hippocampus. These network differences may have widespread impacts on how individuals allocate cognitive resources towards memory and behavior, and mediate the impact of memory-influencing factors such as stressors. 3) In stimulus rich, real-world settings, numerous contextual signals may vie for control of attention and influence what is stored in memory. Extant evidence from rodents suggests that memories may be structured within contextual hierarchies (e.g., memories for a building are stored in relation to the town in which it resides). A broad goal for our research is to understand how spatial and non-spatial memory are structured in humans; preliminary data from our research suggests that contextually grounded hierarchies may be an organizing principle for functions along the rostro-caudal axis of the hippocampus. Our research aims to delineate how contextual traces interact to govern memory formation and retrieval, and to test the mechanisms that allow humans to both flexibly access distinct memories and to use associative structures to generalize across experiences.