Abstract

Episodic memory involves the ability to remember specific events and personal experiences. It shares computational and neural resources with episodic future thinking, or the ability to simulate future episodes in anticipation of situations that have not yet occurred. Activity in the frontal lobe has been associated with episodic memory formation, as functional connectivity between the medial temporal lobe (MTL) and prefrontal cortex (PFC) has been associated with the organization and manipulation of information when forming memories. At its core, episodic memory extends to several other functional domains by recombining past information to construct future scenarios, facilitating an aspect of "mental time travel" by referencing past events to determine optimal outcomes for the future. These processes may be affected by aging, as both memory specificity and hippocampal integrity decrease in normal healthy aging. To better understand the nature of memory-guided decision-making and determine if any age-related differences exist, groups of healthy young and older adults underwent a behavioral task consisting of encoding and decision-making phases while being scanned with fMRI. Study participants encoded a series of naturalistic video stimuli before choosing between sets of options that were presented earlier and reporting on their level of preference for each selection made. A representational similarity analysis (RSA) examined patterns of activations between encoding and decision-making events yielding neural pattern similarity (NPS) scores, which were entered into ANOVA, paired, and independent samples testing. If decision-making was influenced by episodic memory representations of previously encountered stimuli, then we expected to find greater similarity between encoding and decision-making episodes of the chosen compared to the unchosen options. We observed no significant differences in whole brain NPS scores between chosen and unchosen encoding epochs. We also hypothesized that regions involved in the retrieval of event information (MTL, PFC) would demonstrate similar patterns of fMRI activity across encoding and decision-making. A region of interest (ROI) analysis revealed no differences between chosen and unchosen encoding epochs in these specific regions. However, we observed differences between the ROIs when comparing within conditions. The PFC showed greater similarity between encoding and decision-making epochs than both the left and right hippocampi and the left hippocampus exhibited less similarity than the right. The final aim of the study was to compare activation patterns between young and older adults to determine whether there were age-related differences in memory-guided decision-making. There was an interaction between ROI and age group, indicating activity pattern differences between young and older adults across memory-related brain regions. There are several potential factors that may have influenced these outcomes, and future studies may benefit from taking additional measures to refine the pacing, delay times, and duration of stimuli presentation when designing experimental paradigms.

Degree

PhD

College and Department

Family, Home, and Social Sciences; Psychology

Rights

https://lib.byu.edu/about/copyright/

Date Submitted

2024-06-04

Document Type

Dissertation

Handle

http://hdl.lib.byu.edu/1877/etd13707

Keywords

episodic memory, decision-making, fMRI, representational similarity analyses

Language

english

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