Dissertation
Brain-behavior relationships in aging: episodic memory, medial-frontal parietal network, and cognitive reserve
University of Iowa
Doctor of Philosophy (PhD), University of Iowa
Summer 2023
DOI: 10.25820/etd.006882
Abstract
Normal aging entails cognitive and functional decline that could potentially become pathological unless certain lifestyle factors that contribute to protective cognitive effects manage to offset this course. Episodic memory (EM) is a cognitive function that is unmistakably impacted by age-related neurodegeneration, such that the amount of deterioration in EM can even distinguish between normal decline and that caused by Alzheimer’s Disease. EM also critically depends on the hippocampus (HC), a brain structure that is strongly associated with the Medial-Frontal Parietal Network (MFPN). The MFPN is a functional brain network associated with EM processes and undergoes structural and functional reorganization in normal and pathological aging. Both the HC and the MFPN are functionally subdivided in ways that may display heterogeneous aging processes, yet these are not well characterized in older adults in relation to the decline in their EM performance. In the same vein, it is unknown whether and how protective “cognitive reserve” (CR) lifestyle factors buffer the effects of EM decline via the MFPN and its interactions with the HC. For my research, I sought to characterize the HC-MFPN brain-behavior relationship with EM in aging. By determining the assignments of the three HC segments (Head, Body, and Tail) to either of the three MFPN subnetworks (A, B, and C), I prepared a functional brain atlas that served as the basis for processing resting state functional connectivity (rs-fc) data of two independent datasets of older adults to assess the brain-behavior relationship with EM. I further tested this relationship by looking at possible moderator effects from years of education and physical activity as part of a CR framework. I performed hierarchical multiple regressions per subnetwork for each dataset, including exploratory analyses evaluating other CR factors. Regarding my functional atlas, all three hippocampal segments were only significantly affiliated with the MFPN-C (which includes the Medial-Temporal Lobe), thus supporting the MFPN-C’s designation as a “medial-temporal subnetwork”. For the brain-behavior relationship, only MFPN-C rs-fc was related to the Late Learning EM measure of the Auditory-Verbal Learning Test (AVLT) when the exploratory CR factor of verbal intelligence was in the model. MFPN-A rs-fc was marginally significantly related, but no other predictor survived corrections for multiple comparisons in any other model. Overall, my notable results can be summed up by the following two points: (1) all HC segments showed a connection “preference” for MFPN-C, and (2) MFPN-C and less so MFPN-A rs-fc were related to EM performance only when accounting for verbal intelligence. Though some outcomes were unexpected—such as a lack of significant findings concerning performance in the commonly used AVLT Delayed Recall measure—they add to our understanding of the complex and still under-explored nature of rs-fc subnetworks, EM performance, and CR in aging.
Details
- Title: Subtitle
- Brain-behavior relationships in aging: episodic memory, medial-frontal parietal network, and cognitive reserve
- Creators
- Adriana M. Rivera-Dompenciel
- Contributors
- Michelle W Voss (Advisor)Daniel Tranel (Committee Member)Dorit Kliemann (Committee Member)Jeffrey Long (Committee Member)Aaron D Boes (Committee Member)
- Resource Type
- Dissertation
- Degree Awarded
- Doctor of Philosophy (PhD), University of Iowa
- Degree in
- Neuroscience
- Date degree season
- Summer 2023
- DOI
- 10.25820/etd.006882
- Publisher
- University of Iowa
- Number of pages
- x, 75 pages
- Copyright
- Copyright 2023 Adriana M. Rivera-Dompenciel
- Language
- English
- Date submitted
- 07/21/2023
- Description illustrations
- color illustrations
- Description bibliographic
- Includes bibliographical references (pages 68-75).
- Public Abstract (ETD)
As we age, certain brain functions start to typically show a decline in performance, memory being one of the most affected. Though there are many brain factors involved in age-related memory decline, I am interested in studying one in particular: a collection of brain regions that form a network crucial for memory. This study is important because aging researchers typically focus on only one region without considering the networks or larger systems with which they interact for successful memory. For my research, I first analyzed the brain scans of older adults to create a network map of important memory brain regions, and then I examined how the connections within this memory network relate to memory performance. I also looked at whether certain lifestyle factors such as early life education impact the relationship between memory network function and memory performance in aging.
For the memory network map, results showed that the essential brain regions for memory (known collectively as the hippocampus) are most strongly connected to a specific subnetwork that includes regions the hippocampus is known to work with for relaying information to the rest of the brain for memory formation. When looking at the relationship between memory subnetworks and memory performance, I found that having stronger connections specifically within this hippocampal subnetwork was related to higher memory performance in a word list test only when accounting for verbal intelligence. However, lifestyle factors like early education and physical activity did not show a significant relationship with (or modify the relationship between) the memory network and memory performance in this study.
- Academic Unit
- Interdisciplinary Graduate Program in Neuroscience
- Record Identifier
- 9984454643402771
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