Date of Award

8-12-2016

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Psychology

First Advisor

Tricia Z. King, PhD

Second Advisor

Daniel L Drane, PhD

Third Advisor

Bruce Crosson, PhD

Fourth Advisor

Jessica Turner, PhD

Abstract

Verbal memory deficits are among the most prominent cognitive sequelae in individuals with left temporal lobe epilepsy (LTLE). However, relationships between verbal memory function and white matter integrity (WMI) in the left temporal lobe remain unclear. Current study aims included determining fractional anisotropy (FA) and mean diffusivity (MD) differences as an index of WMI between participants with left temporal lobe epilepsy (LTLE), participants with right TLE (RTLE), and controls, establishing group differences based on verbal memory function between TLE groups, and describing relationships between WMI and verbal memory function within TLE groups. Probabilistic tractography defined the left fornix (FRX), left uncinate fasciculus (UF), left parahippocampal cingulum (PHC), and a control region, the left corticospinal tract (CST), in 26 LTLE, 29 RTLE, and 20 control participants. The LTLE group demonstrated significantly lower fractional anisotropy (FA) along the PHC compared with controls. LTLE and RTLE groups did not differ significantly on measures of verbal memory until analyses were restricted to participants with left-lateralized language functioning. PHC FA was negatively correlated with semantic memory function in LTLE, but positively associated with episodic memory functioning in RTLE. Overall, findings highlight the PHC as vulnerable in LTLE, and differentially related to verbal memory functioning based on TLE group. Both findings are likely secondary to left-lateralized white matter disruption in LTLE. The current study also highlighted the importance of identifying homogenous groups to more clearly identify brain-behavior relationships. Current findings further define left-lateralized white matter alternations and related verbal memory deficits in TLE. Implications for these findings are presented in context with previous TLE literature, and future directions for further study are discussed.

Available for download on Saturday, July 21, 2018

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