Testing a Novel Theoretical Framework for the Human Medial Temporal Lobes in Perception and Memory During Spatial Navigation

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 DESCRIPTION (provided by applicant): The goal of this project is to test a novel theoretical framework that relates memory and navigation functions of the human medial temporal lobes. While numerous studies in rats and humans suggest the importance of the medial temporal lobes to navigation and memory, these two functions remains poorly linked. Our theoretical framework argues that damage to the human medial temporal lobes results in deficits in both high-resolution perception and binding of details in memory. Thus, one prediction of this model is that patients with medial temporal lobe damage will show deficits in encoding high-resolution spatial details during navigation. This will manifest specifically in impairments in spatial precison during navigation rather than whether patients use distal landmarks (allocentric) or self-orientation (egocentric) cues to navigate. This contrasts with other models of navigation that suggest that MTL damage will impair allocentric but not egocentric navigation. We will test our model by having patients navigate a large arena, searching for a hidden platform, and compare their performance with a group of age and IQ matched healthy controls. A second prediction of our model is that medial temporal lobe damage will impair binding of spatiotemporal details during navigation. We will test this prediction of our model by comparing patient performance when they must remember multiple spatial locations over trials. We expect patient performance to worsen as a function of the number of locations they must remember compared to controls. This contrasts with the predictions of other models of navigation and memory, which suggest impairments in allocentric memory regardless of the number of locations the patient must remember. Our model thus provides novel yet testable predictions that this R03 seed grant will be instrumental in helping us to develop. Use of innovative tools such as virtual reality and high-resolution magnetic resonance imaging (MRI) targeting the medial temporal lobes will also further our understanding of how neural disease such as stroke impacts both brain function and cognition more generally.