Dynamic neural connectivity of autobiographical memory retrieval processes Open Access

Abstract

The brain is comprised of dynamic networks of functional regions that interact with one another to execute various processing demands. Autobiographical memory (AM) involves the orchestration of multiple cognitive processes that evolve over time, including memory access and subsequent elaboration. Previous neuroimaging studies have contrasted memory access and elaboration processes in terms of regional brain activation and connectivity within coordinated multi-region networks rather than between specific regions like the hippocampus and prefrontal cortex (PFC). The purpose of the present studies was to determine the changes in interregional connectivity strength across AM retrieval processes to understand network level mechanisms of AM retrieval and test theoretical accounts of dynamic AM retrieval processes. In two AM retrieval experiments, we predicted that dynamic (time-varying) connections would reflect early memory-access related connections between hippocampal and PFC regions and a separate set of later, elaboration-related connections between lateral frontal working memory regions and parietal/occipital visual imagery regions. In both studies, healthy adults generated AMs from neutral cue words in a pre-scan session and were later cued to retrieve the AMs while being scanned with fMRI. We used a moving-window graph theory analysis to examine dynamic changes in the strength of connectivity among regions involved in AM retrieval. In addition, we examined the extent to which these core AM retrieval regions became more or less central to integrating distributed information throughout a whole brain network. In particular, in both studies, dynamic network analyses showed that early, access-related processing involved a primarily anterior, fronto-temporal network associated with strategic search and initial reactivation of specific episodic memory traces. In addition, in line with predictions, brain network connectivity during later retrieval processes primarily included strong connections between occipital-parietal regions and fronto-parietal regions associated with mental imagery, reliving, and working memory processes. Taken together, these studies particularly help refine and extend dynamic neural processing models of AM retrieval, like the self-memory system theory, by providing evidence of the specific connections throughout the brain that change in their synchrony with one another as processing progresses from access of specific events in the past to elaborative reliving of the past event.

Table of Contents

Table of Contents

List of Tables.......................................................................................................................ii

List of Figures ....................................................................................................................iii

General Introduction ...........................................................................................................1

Autobiographical memory retrieval: Cognitive Processes .....................................5

Autobiographical memory retrieval: Neural Processes ........................................10

Autobiographical Memory Retrieval: Functional Integration and Connectivity...18

The present study .................................................................................................. 26

Study 1: Dynamic functional connectivity changes between access and elaboration of autobiographical memories ...............................................................................................39

Introduction ...........................................................................................................39
Method ..................................................................................................................54

Results ...................................................................................................................73

Discussion .............................................................................................................81

Study 2: Large-scale functional network organization changes across autobiographical memory retrieval processes ..............................................................................................96

Introduction ..........................................................................................................96

Method ................................................................................................................113

Results .................................................................................................................130

Discussion ...........................................................................................................151

General Discussion .........................................................................................................170

References ......................................................................................................................184

List of Tables

Study 1

Table 1. Region of Interest (ROI) hemisphere, label, and MNI coordinates.........63

Table 2. Connections with stronger connectivity early versus late and late versus early.......................................................................................................................78

Study 2

Table 1. Region of Interest (ROI) hemisphere, label, and MNI coordinate........118

Table 2. Connections with stronger connectivity early versus late 1 period..................................................................................................................136

Table 3. Connections with stronger connectivity during the late 1 versus early period..................................................................................................................139

Table 4. Connections with stronger connectivity late 2 versus early period......142

Table 5. Connections with stronger connectivity late 3 versus early period......145

Table 6. Top 10% most change in degree centrality for whole brain network nodes by time period...........................................................................................149

List of Figures

Study 1

Figure 1. Illustration of an AM retrieval trial........................................................60

Figure 2. Illustrations of core network ROIs.........................................................64

Figure 3. Illustration of core network ROIs from a) dorsal sagittal and b) ventral axial perspective....................................................................................................68

Figure 4. Stable network during AM retrieval......................................................75

Figure 5. Stronger connections early versus late in AM retrieval........................77

Figure 6. Stronger connections late versus early in AM retrieval........................79

Study 2

Figure 1. Illustration of an AM retrieval trial.....................................................115

Figure 2. Illustrations of core network ROIs......................................................119

Figure 3. Illustration of core network ROIs from a) dorsal sagittal and b) ventral axial perspective..................................................................................................124

Figure 4. Stable network during AM retrieval....................................................132

Figure 5. Stronger connections early versus late 1 in AM retrieval...................135

Figure 6. Stronger connections late 1 versus early in AM retrieval...................138

Figure 7. Stronger connections late 2 versus early in AM retrieval...................141

Figure 8. Stronger connections late 3 versus early in AM retrieval...................144

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School	Laney Graduate School
Department	Psychology
Degree	PhD
Submission	Dissertation
Language	English
Research Field	Psychology, Psychobiology Psychology, Cognitive
Keyword	Memory Retrieval Graph Theory Dynamic functional connectivity Autobiographical Memory Functional MRI
Committee Chair / Thesis Advisor	Hamann, Stephan, Emory University
Committee Members	Manns, Joseph, Emory University Bauer, Patricia, Emory University Rilling, James K, Emory University James, G. Andrew, Dilks, Daniel D, Emory University

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