Master of Science
How brain activity is synchronized across individuals during narrative comprehension has previously been characterized by functional magnetic resonance imaging (fMRI) in healthy and patient populations. To our knowledge, there has been limited investigation as to how it is affected by major depressive disorder (MDD). We addressed this issue with fMRI through examination of inter-subject synchronization in the default mode network (DMN), brain structures which have previously been implicated in MDD pathology. Twenty-two patients with MDD and 20 matched control participants listened to Intact versus Scrambled versions of an auditory narrative; these experimental conditions differed in the degree of temporal integration they demanded. Across conditions, we found a significant increase in synchrony within DMN for intact narratives. As compared to controls, patients demonstrated a significant increase in synchrony across multiple DMN regions, some specific for intact narratives. Our findings highlight the impact of brain abnormalities in MDD on an ecologically relevant cognitive function.
Summary for Lay Audience
How we take in and make sense of information is key to how we interact with the world around us. When we listen to a story, the way the brain integrates it is similar between people. We take different senses together and bind them in levels which pass along information as they become more complex. Therefore, we can study this process by measuring how similar activity is in different brain regions when participants are listening to a story and when the story is disrupted. Previous studies found that areas of the default mode network play a key role in making sense of stories. Researchers used the story 'Pie-man,' in healthy and some patients but it is unknown in patients with depression. Those with depression have difficulties related to changes in the brain involved in story processing. The goal of this study was to examine if those differences would impact how the story is processed. We scanned 22 clinically depressed patients and 20 controls in functional magnetic resonance imaging while they listened to Intact and Scrambled story. By changing the amount of information presented, we can see if the brain signal is consistent with others scanned. When information is disrupted, we found that patients with depression showed a similar change to controls. However, folks with depression showed a higher consistency in some regions compared to controls. Overall, we showed a difference in how the brain processes stories differently in depression. These findings shed a new light on how information processing is affected by depression. This could inform treatments which target the affected brain area
Liang, Darren Ri-Sheng, "Role of the default-mode network during narrative integration in major depressive disorder" (2022). Electronic Thesis and Dissertation Repository. 8724.
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Available for download on Friday, August 18, 2023