Neurofunctional Correlates of Geometry and Feature Use in a Virtual Environment Across the Lifespan
Forloines, Martha Reeves
Type of DegreePhD Dissertation
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There are mixed results regarding the differentiation of neurofunctional correlates of spatial abilities. To help elucidate the existing mixed findings, three experiments were conducted. In Experiment 1, college-aged participants completed a virtual navigation task in which they learned the relationship between landmarks, environmental features, and a goal. The goal was a distinct landmark, or feature, consistently situated in one corner, or a geometric cue, of a rectangular room. Test trials varied the relationship of featural and geometric cues allowing insight into navigational strategies when using these cues. Results showed participants learned the task rapidly, and utilize both landmark and environmental geometry strategies to locate the goal; preferring the feature-based strategy. These results allowed for confidence to transfer the task into the 7 Tesla (T) Magnetic Resonance (MR) scanner in Experiment 2 with a similar sample. This experiment was conducted using functional Magnetic Resonance Imaging (fMRI) to determine neurofunctional correlates of environmental geometry and feature strategies. Behavioral results mimicked Experiment 1. Functional results showed activations in various navigationally relevant regions, such as the parahippocampus and caudate across strategies. Experiment 3 employed the same task with older adults (36-59 years old) to explore age differences in behavior or neurofunction. Behavioral results showed no differences across ages. Functional results revealed similar activations in navigationally relevant regions during the task. A comparison of neurofunction across ages was conducted to examine age differences. One finding was differential activation of the parahippocampus across trial types and ages. Finally, volumetric comparisons were conducted on the hippocampus and caudate across ages. These results add to the knowledge of the neural function of these regions and the stability of the human navigation network across ages, and may inform our understanding of abnormal aging.