Date of Award

Fall 10-15-2024

Embargo Period

10-15-2024

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Neuroscience

Additional Department

Psychiatry and Behavioral Sciences

College

College of Graduate Studies

First Advisor

Jane Joseph

Second Advisor

Amber Jarnecke

Third Advisor

Jens Jensen

Fourth Advisor

Kevin Gray

Fifth Advisor

Judson Chandler

Sixth Advisor

Kathryn Magruder

Abstract

Significance. Memory disturbances for emotional content are central to PTSD, yet most research focuses on trauma memories. Recent evidence suggests that enhancing access to positive memories could improve mood, affect regulation, self-esteem, and integration of trauma memories. However, the neurocognitive mechanisms underlying positive memory encoding in PTSD are poorly understood. No study has examined memory for positive social items in PTSD, which is important because PTSD entails social withdrawal and reduced accessibility to positive memory. Additionally, positive memories embedded in a social context have enhanced subjective value and strengthening their accessibility may confer greater benefits to wellbeing compared to non-social positive memories. Approach. Adults with PTSD (N=14) and trauma-resilient control individuals (TRC, N=18) completed a social reward task during functional magnetic resonance imaging. In this task, participants received evaluations according to whether unfamiliar peers “expected to like” the participant if they met in real life. Evaluations received were either favorable or neutral (i.e., no rating). Post-scanning, participants completed an episodic memory exercise wherein they indicated who had rated them favorably or did not rate them at all. Contrasts between successfully encoded social conditions were examined at the voxel-level with psychophysiological interaction using the bilateral amygdala (AMY) as seeds and hippocampi (HIP) as primary ROIs. Post-hoc general linear models (GLMs) were conducted to probe moderation by diagnosis and symptom severity. Recognition performance was similarly assessed using GLMs considering diagnosis, valence, diagnosis x valence, and sex as a covariate. Findings. No recognition performance differences emerged between PTSD and TRC groups, and AMY-HIP connectivity differences were limited to the neutral condition. Whereas functional uncoupling occurred during neutral memory encoding for TRCs, AMY-HIP co-activation was observed in PTSD. Symptom severity did not explain variability in AMY-HIP connectivity within the PTSD sample. Conclusions. Although positive memories may have distinct phenomenological characteristics in PTSD samples, quantitative indices of performance for rewarding social memories are similar between PTSD and TRC individuals. Notwithstanding, individuals with PTSD may inappropriately activate emotional memory networks in neutral contexts, suggesting an overgeneralization of emotional processing. Thus, this study provides evidence of dysfunctional emotional memory processing in non-trauma, neutral situations within PTSD samples.

Rights

Copyright is held by the author. All rights reserved.

Download

Share

COinS