Samanez-Larkin, Gregory RGreen, Mikella Alexis2023-06-082023-06-082023https://hdl.handle.net/10161/27686<p>Physical activity has many benefits including promoting healthy aging, reducing risk of chronic disease, and supporting general well-being. Despite this, many adults do not get significant amounts of daily physical activity. The effects of interventions promoting physical activity are highly variable and typically modest. Even when behavioral interventions are effective, the understanding of how and why they work is lacking. Understanding the determinants of physical activity behavior change, along with identifying evidence-based behavior change techniques that target these determinants, is critical for developing effective interventions. In this dissertation, across two studies, I examine the role of neural and behavioral determinants of physical activity behavior change. Chapter 1 provides a review of the two prominent theoretical approaches to physical activity behavior change, social cognitive theory and dual-process theory, and highlights how neuroimaging techniques can be utilized to help inform gaps in both theoretical and applied knowledge of physical activity. Chapter 2 (Study 1) evaluates if there are brain regions correlated with physical activity behavior change. In the study, participants wore a pedometer for a week before and after an fMRI session where they read and heard statements about walking. Behavioral analysis demonstrated that participants walked significantly more following exposure to the walking-related messages. Whole-brain analysis examined regions positively associated with walking behavior change and produced two significant clusters in the frontal pole region and the precuneus/posterior cingulate gyrus region. The frontopolar cortex is implicated in pre-commitment, a self-control strategy where people anticipate self-control failures and prospectively restrict their access to tempting alternatives. The precuneus/posterior cingulate cortex region has been found to play a role in self-relevant processing. Both self-control and self-relevant processing are believed to be important for behavior change. Chapter 3 (Study 2) focuses on neural and self-report responses to different types of health messages and their ability to predict physical activity behavior change. In the study, participants completed an fMRI task where they read positively or negatively framed walking-related messages with either social or non-social based content and rated how personally motivating they were as well as other self-reported ratings. Neural activity in regions involved in positive valuation and self-referential processing were measured to evaluate whether sensitivity in these regions to individual messages could predict the effectiveness of those messages when delivered in an intervention weeks or months later. For the next 80 days, participants completed a SMS-based mHealth intervention where they received one of the same walking-related messages from the scanner task daily. We assessed physical activity using a wearable fitness tracker throughout the 80 days and a baseline period. Individual participant ratings on how relevant the message would be to others predicted the effectiveness of the messages. People were more physically active on days when they received messages that were rated as more relevant to others. Brain activation in the regions of interest selected were not associated with message effectiveness during the intervention. </p>NeurosciencesPsychologyBehavior changePhysical activityDissertation