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There is now a CONTENT FREEZE for Mercury while we switch to a new platform. It began on Friday, March 10 at 6pm and will end on Wednesday, March 15 at noon. No new content can be created during this time, but all material in the system as of the beginning of the freeze will be migrated to the new platform, including users and groups. Functionally the new site is identical to the old one. webteam@gatech.edu
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Name: Jimmy Y. Zhong
School of Psychology – Ph.D. Dissertation Defense Presentation
Date: Tuesday, April 30, 2019
Time: 11:00 am
Location: Conference room, GS/GT Center for Advanced Brain Imaging (CABI)
Advisor: Scott D. Moffat, Ph.D.
Ph.D. Dissertation Committee:
Scott D. Moffat, Ph.D. (Committee Chair; Georgia Tech)
Christopher K. Hertzog, Ph.D. (Georgia Tech)
Paul M. Verhaeghen, Ph.D. (Georgia Tech)
Mark E. Wheeler, Ph.D. (Georgia Tech)
Roberta L. Klatzky, Ph.D. (Carnegie Mellon)
Title: The Impact of Two Spatial Strategies on Entorhinal and Hippocampal Involvement in Visual Path Integration
Summary: Previous neuroimaging and neuropsychological studies showed inconsistent findings concerning the involvement of the hippocampal formation in path integration, and the current study investigated the extent to which the hippocampus proper, the entorhinal cortex, and neocortical regions were activated based on the implementation of continuous and configural updating strategies (one per participant) when performing a virtual path completion task. While configural updating required allocentric encoding of the outbound path’s shape, continuous updating required constant tracking of egocentric movements with reference to a point of origin. Findings from in-lab behavioral testing (Experiment 1) showed that neither strategy elicited more accurate path integration performance than the other, and that gender/sex moderated strategy use. Specifically, male configural updaters outperformed female configural updaters on almost all types of path integration errors, and female continuous updaters outperformed female configural updaters in terms of distance error measures. A subsample of participants who completed Experiment 1 continued to perform new path integration trials with the same strategy during fMRI scanning (Experiment 2). Their brain activation patterns were examined and compared based on whole-brain and region-of-interest (ROI) analyses. A within-trial ROI analysis of activation patterns showed that continuous updaters exhibited significant activation in the left entorhinal cortex based on a contrast of activations derived from simple and complex paths [complex > simple] during the homebound phase. Marginally significant activations in the left hippocampus in both strategy groups were also found based on ROI analysis and same type of descriptive contrast. In each strategy group, within-trial analysis at the whole-brain level further showed significant non-contrast-related patterns of activations (in the left parietal cortex) and deactivations (in the right medial prefrontal cortex and right lateral temporal lobe) during the homebound phase of simple paths. In addition, brain-behavior correlations associated individual differences in visual path integration with non-contrast-related functional activity changes in the occipito-parietal and inferior frontal regions, but not in the hippocampus or the entorhinal cortex. Taken together, these fMRI findings suggest that extrahippocampal attentional and perceptual processes facilitated visual path integration, and that the entorhinal cortex and hippocampus may be more involved in detecting switches in homing decisions or responses between paths of varying complexity than in monitoring performance changes over a single category of paths.
