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.