DOI

10.17077/etd.c3ewilbl

Document Type

Dissertation

Date of Degree

Fall 2015

Degree Name

PhD (Doctor of Philosophy)

Degree In

Neuroscience

First Advisor

Daniel Tranel

Second Advisor

Matthew A. Howard

First Committee Member

Natalie Denburg

Second Committee Member

Michelle Voss

Third Committee Member

Gary Russell

Abstract

My dissertation focused on understanding how different areas of the brain coordinate in networks to drive higher cognitive functions, and how damage, changes the brain’s synchronized activity (or functional connectivity) in the short and long term. In this dissertation, I studied the functional connectivity of brain networks that are thought to underlie emotion and decision-making, and how these networks change in the face of neurological injury.

In my first set of experiments, I studied participants with chronic focal brain damage to determine how damage to brain areas which have been identified as important in emotion and decision-making behaviors (amygdala, ventromedial prefrontal cortex, & insula), affected connectivity of brain networks, and how changes in connectivity following damage to these areas related to emotion and decision-making behavior. Supporting my predictions, I found evidence that damage to the amygdala, ventromedial prefrontal cortex, and insula all result in significantly weaker connections between a network of areas important for assigning value to stimuli. Additionally, I found that stronger connectivity in this valuation network was significantly positively associated with performance on ratings of disgusted faces, while stronger connectivity in a network important for processing emotional salience was significantly positively correlated with decision-making performance.

In the second set of studies in this dissertation, I utilized a population of epilepsy patients who were undergoing brain surgery to treat their seizures to investigate how a brain network related to emotional salience changed from before to after surgery. This approach allowed me to study how the connectivity and associated behavior of this network changed from preoperative baseline, to the weeks and months after part of this network was removed. While I expected a decline in this network in the weeks following surgery, instead I found a significant positive correlation between preoperative and acute postoperative connectivity in a subset of this network. However, my hypothesis that there would be a significant increase in the connectivity of this network between acute and chronic postoperative epochs was supported. I only have partial evidence for a significant correlation between the change in salience network connectivity between preoperative and acute postoperative assessments and the associated change in decision-making behavior. This correlation was in the opposite direction of my hypothesis, with increased change in connectivity being positively associated with change in risk-taking behavior. I did not observe a significant correlation between the change in network connectivity and change in behavior across acute and chronic measurements.

These findings provide important insight on how measures of network connectivity can inform theories of neuroplasticity and reorganization following brain damage. Understanding how these networks change over time, and how changes in these networks relate to behavioral outcomes, are critical for the development and effective deployment of therapeutic interventions. Together, these studies provide a foundation for further study, demonstrating that these networks change over time with damage, and the residual network strength is associated with performance on measures of emotion and decision-making.

Public Abstract

Imagine a rowing team in a race. Each rower is synchronized with the others, so if one of the rowers drops their oar in the water, the entire team needs to readjust, or the boat may start going in circles. My dissertation focused on understanding how different areas of the brain coordinate in networks to drive higher cognitive functions, and how damage, like the loss of an oar, changes the brain’s synchronized activity (or functional connectivity) in the short and long term. In this dissertation, I studied the functional connectivity of brain networks thought to underlie emotion and decision-making, and how these networks change in the face of neurological injury. I studied these questions in two patient populations. In my first set of experiments, I studied participants with chronic focal brain damage to determine how damage to brain areas which have been identified as important in emotion and decision-making behaviors (amygdala, ventromedial prefrontal cortex, & insula), affected connectivity of brain networks, and how changes in connectivity following damage to these areas related to behavior. Supporting my predictions, I found evidence that damage to the amygdala, ventromedial prefrontal cortex, and insula all result in significantly weaker connections in a network of areas important for assigning value, and that stronger connectivity in this valuation network was significantly positively associated with ratings of disgusted faces. Meanwhile, stronger connectivity in a network important for processing emotion was significantly positively correlated with decision-making performance. In the second set of studies in this dissertation, I utilized a population of epilepsy patients who were undergoing brain surgery to treat their seizures to investigate how a brain network related to emotion processing changed from before to after surgery. I found a significant positive correlation between the connectivity in this network before and in the weeks following surgery. I also found a significant increase in this network between the weeks following surgery, and six months after the operation. I did not find strong evidence that these network changes were linked to changes in emotion recognition or decision-making.

These findings provide important insight on how measures of network connectivity can inform theories of about how the brain changes following brain damage. Understanding how these networks change over time, and how changes in these networks relate to behavioral outcomes are critical for the development and effective timing of therapeutic interventions. Together, these studies provide a foundation for further study, demonstrating that these networks change over time with damage, and these networks are associated with performance on measures of emotion and decision-making.

Keywords

decision-making, emotion, functional connectivity, plasticity

Pages

xxi, 248 pages

Bibliography

Includes bibliographical references (pages 229-248).

Copyright

Copyright © 2015 Matthew James Sutterer

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