White Matter Correlates of Dissociation in a Diverse Sample of Trauma-Exposed Women Público

Abstract

Dissociation is a common trauma response to trauma linked to functional brain disruptions in brain networks subserving emotion regulation and multisensory integration; however, structural neural correlates of dissociation are less known, particularly abnormalities in stress-sensitive white matter (WM) tracts. The present study examined associations between dissociation and WM microstructure, assessed via fractional anisotropy (FA), in a large, diverse sample of women recruited as part of a long-standing trauma study, the Grady Trauma Project (GTP). As part of GTP, 135 trauma-exposed women (18-62 years old, M = 34.25, SD = 12.96, 84% self-identifying as Black) were recruited, received diffusion-weighted imaging, and completed the Multiscale Dissociation Inventory (MDI); FA values were extracted from ten major WM tracts of interest. Partial correlations were conducted to examine associations between dissociation facets (MDI total and subscales) and FA while covarying age and temporal signal-to-noise ratio; false discovery rate corrected p < .05 indicated statistical significance. FA in seven tracts showed significant negative associations with overall dissociation (MDI total score; rs < -.19, pFDR < .05); the corona radiata, corpus callosum, superior longitudinal fasciculus, thalamic radiation, anterior cingulum, fornix, and uncinate fasciculus. Among facets of dissociation, FA was most consistently associated with dissociative memory disturbance, showing a significant and negative association with all but one of tracts of interest, (rs < -.23, pFDR < .05). Our findings indicated that dissociation severity was linked to proportionally lesser WM microstructural integrity in tracts involved with sensory integration, emotion regulation, memory, and self-referential processing. Disruptions in these pathways may underlie dissociative phenomena, representing important psychotherapeutic and neuromodulatory targets.

Table of Contents

Table of Contents

1. Disclosure……………………………………………………………………………………......................................................................................... 1

2. Abstract………………………………………………………………………………………......................................................................................... 2

3. Introduction……………………………………………………………………………………..................................................................................... 3

3.1. Models of Dissociation……………………………………………………………………...................................................................................… 4

3.2. Neurobiology of Dissociation…………………………………………………………….................................................................................….. 5

3.2.1. Neurocircuitry of Fear…………………………………………………………………….................................................................................... 6

3.2.2. Triple Network Model and Relations to PTSD and Dissociation…………....................................................................................……. 7

3.2.3. Other Neurobiological Models of PTSD and Dissociation…………………..................................................................................……... 7

3.2.4. White Matter and Dissociation………………………………………....................................................................................................…. 8

3.3. Current Study……………………………………………………………..................................................................................................…….. 10

4. Methods………………………………………………………………….......................................................................................................……. 11

4.1. Participants and Procedure………………………………………………….....................................................................................…….……. 11

4.2. Clinical Assessments………………………………………………………………….....................................................................................….. 13

4.2.1. Exploratory Clinical Assessments…………………………………………......................................................................................….…... 16

4.3. MRI Acquisition and Image Processing…………………………………...........................................................................................……… 17

4.4. Statistical Analyses………………………………………………………………………...................................................................................… 19

4.4.1. Exploratory Statistical Analyses…………………………………....................................................................................................……. 20

5. Results…………………………………………………………………...............................................................................................…..………... 21

5.1. Primary Analysis……………………………………………...........................................................................................................………… 21

5.2. Secondary Analyses…………………….....................................................................................................................................……... 22

5.3. Sensitivity Analyses………………………...............................................................................................................................………... 22

5.4. Exploratory Analyses…………………………............................................................................................................................………. 23

6. Discussion………………………………………...............................................................................................................................………. 24

6.1. Review of Study…………………………………........................................................................................................................…………. 24

6.2. Previous Literature………………………………………………………......................................................................................…..…………. 24

6.3. Primary and Secondary Analyses………………………………………..................................................................................…..…………... 25

6.3.1. Sensitivity Analyses……………………………………………………….....................................................................................…………… 27

6.3.2. Exploratory Analyses……………………………………………………….................................................................................…………….. 28

6.4. Implications…………………………………………………………………......................................................................................…………… 30

6.5. Limitations and Future Directions…………………………………………………..............................................................................………. 33

6.6. Conclusion…………………………………………………………………..........................................................................................…………. 35

7. References………………………………………………………….........................................................................................………..……………. 37

Table 1. Types of traumas experienced by percentage and frequency…………............................................................................………….. 51

Table 2. Scanner details and acquisition parameters……………………………….............................................................................………… 52

Figure 1. Masks of white matter pathways of interest…………………………………….............................................................................….. 53

Table 3. Mean and standard deviation of tSNR values and fractional anisotropy for all tracts, all scanners, before harmonization………...… 54

Table 4. Clinical and Demographic Characteristics (N=135)……………………………..........................................................................……... 55

Table 5. Correlations between harmonized PTSD symptom scores and Multiscale Dissociation Inventory Subscale Scores…….……....……… 57

Table 6. Correlations between harmonized tract fractional anisotropy and clinical and demographic characteristics………….................….. 58

Figure 2. Associations among dissociation and white matter microstructure (N=135)………...................................................................… 59

Figure 3. Significant associations among dissociation symptoms and tract FA…………....................................................................……... 60

Table 7. Partial correlations between harmonized tract fractional anisotropy and Multiscale Dissociation Inventory scores with age and

temporal signal-to-noise ratio as covariates......................................................................................................................................... 62

Table 8. Partial correlations between harmonized tract fractional anisotropy and Multiscale Dissociation Inventory scores with age,

temporal signal-to-noise ratio, and harmonized PCL-5 scores as covariates…......................................................................................... 64

Table 9. Partial correlations between harmonized tract fractional anisotropy and Multiscale Dissociation Inventory scores with age and

temporal signal-to-noise ratio as covariates including only participants who identified as Black……….......................................……..…... 66

Table 10. Mediation analyses examining MDI score as a mediator of the relationship between PCL-5 score and harmonized tract FA…....... 68

Table 11. Mediation analyses examining PCL-5 score as a mediator of the relationship between MDI score and harmonized tract FA…...…. 69

Table 12. Partial correlations between Multiscale Dissociation Inventory scores and Letter N-Back Task Performance and CAPS-5 item D1

severity with age as a covariate…....….............................................................................................................................................….. 70

About this Honors Thesis

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School	Emory College
Department	Neuroscience and Behavioral Biology
Degree	B.S.
Submission	Honors Thesis
Language	English
Research Field	Psychology, Behavioral Sciences Psychology, Clinical Psychology, Psychobiology
Palabra Clave	Women Memory Fractional ansiotropy PTSD Dissociation Trauma White matter microstructural integrity Sensorimotor integration
Committee Chair / Thesis Advisor	Negar Fani, Emory University
Committee Members	Ali Cohen, Emory University Mar Sanchez, Emory University

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