Name: Jenny Walker

School of Psychology – Dissertation Defense Meeting

Date: Wednesday, April 23, 2025

Time: 11:00am

Location: GT/GSU Center for Advanced Brain Imaging (CABI), Conference Room, 831 Marietta St NW, Atlanta, GA, 30318

Remote Access: Zoom link available upon request. To request, email jenny.walker@gatech.edu

Dissertation Advisor: Mark Wheeler, Ph.D. (Georgia Tech)

Dissertation Committee Members:

Thackery Brown, Ph.D. (Georgia Tech)

Hsiao-Wen Liao, Ph.D. (Georgia Tech)

Rick Thomas, Ph.D. (Georgia Tech)

Madeleine Hackney, Ph.D. (Emory University)

Title: How Does a Current Perceptual Decision-Making Model Carry Forward to Older Adult Samples? A Comparative & Hierarchal Exploration of Bold Signal Timecourses

Abstract: Perceptual decision-making (PDM) is a shift from perception to behavior and occurs in a series of stages, including sensory processing, evidence accumulation, and the moment of decision. Prior research with younger adults has identified brain regions of interest (ROI) correlates to these stages. The goal of this work was to explore the generalizability of those findings in an older adult sample. The structure and function of brain regions often change across the lifespan, and it is unclear if these ROI correlate findings will hold. Using a subset of data from my master’s thesis and a second study with a similar protocol, PDM task-related behavior and blood oxygen level-dependent (BOLD) activity of younger (18-35 years) and older (60-80 years) were compared. First, to assess the utility of these data for subsequent analyses, accuracy and reaction time data were assessed. The reaction time distributions were inspected for the timing requirements of a neuroimaging analysis. Potential PDM task-related strategies were characterized through drift diffusion modeling. The magnitude and temporal parameters of BOLD timeseries functions were compared across age groups within ROIs. Those timeseries were then analyzed through an exploratory hierarchal clustering analysis. Due to data quality concerns, the neuroimaging analyses were specific to the moment of decision ROIs. There is evidence that older adults may have approached these tasks from a comparatively conservative approach by setting a higher threshold for evidence while making choices amongst competing options. There were few differences by age in moment of decision ROIs, but older adult data yielded fewer clusters and more dissimilar left/right striatum activity than younger adults. Such findings could be indicative of more generalizability of function across regions in older adults than younger adults, albeit the most insightful differences may be more likely to lie in sensory or evidence accumulation ROIs. This area of inquiry and approach is novel, so advice for future researchers is provided.