Neural mechanisms underlying effort-related choice and action Restricted; Files Only
Suzuki, Shosuke (Summer 2025)
Abstract
Many activities essential to our health and wellbeing require the expenditure of effort. Understanding the neural mechanisms underlying effortful behavior is therefore not only a fundamental question of behavioral neuroscience but also critical for elucidating the pathophysiology of motivational deficits. While the ventral striatum (VS) and dorsomedial prefrontal cortex (dmPFC) have been consistently implicated in effort-based decision-making (EBDM), their specific contributions to effort-related choice and action remain unresolved. Traditional EBDM paradigms have typically imposed artificial temporal constraints (e.g., by isolating decision and action phases) that limit their ecological validity. This dissertation employed naturalistic, immersive paradigms to better capture the dynamic interplay between choice and action involved in effortful behavior. In the first study, participants completed a virtual maze-navigation task while undergoing functional magnetic resonance imaging (fMRI). We identified functionally distinct subregions within the striatum: A dorsomedial region encoding anticipatory and initiatory effort signals, a putamen region associated with movement, and an anterior VS region in which reward responses were attenuated following effortful navigation, consistent with effort discounting. These regions displayed distinct corticostriatal connectivity and mapped on closely to established connectivity-based parcellations of the striatum. Notably, we found opposing influences of effort activation and discounting signals during an independent EBDM task, offering a plausible explanation to prior inconsistencies in the literature regarding the role of VS in encoding effort-discounted value signals. In the second set of studies, we used a naturalistic virtual foraging task and non-invasive temporal interference (TI) stimulation to assess the causal role of dmPFC in modulating the affective consequences of effort. TI stimulation to the dmPFC attenuated the negative impact of effort on mood, suggesting a regulatory function for this region in integrating internal state and external effort demands during real-time decision-making. Together, these studies demonstrate the value of naturalistic paradigms for revealing temporally and anatomically dissociable neural mechanisms that are obscured in conventional tasks. By highlighting the functional heterogeneity of the VS and the affective regulatory role of the dmPFC, this work advances our understanding of the functional neuroarchitecture supporting effort-related choice and action, and informs translational research targeting motivational deficits in clinical populations.
Table of Contents
CHAPTER 1: INTRODUCTION 1
CHAPTER 2: DISTINCT REGIONS OF THE STRIATUM UNDERLYING EFFORT, MOVEMENT INITIATION AND EFFORT DISCOUNTING 10
Figure 2.1 15
Figure 2.2 18
Figure 2.3 20
Figure 2.4 22
Figure 2.5 24
Supplementary Tables 2.1-2.2 54
Supplementary Figures 2.1-2.3 56
CHAPTER 3: TEMPORAL INTERFERENCE STIMULATION TO THE DORSOMEDIAL PREFRONTAL CORTEX MODULATES THE IMPACT OF EFFORT ON MOOD DURING NATURALISTIC FORAGING 59
Figure 3.1 / Table 3.1 64
Figure 3.2 66
Table 3.2 67
Figure 3.3 70
Figure 3.4 72
Supplementary Table 3.1 97
Supplementary Figures 3.1-3.4 98
CHAPTER 4: CONCLUSION 102
About this Dissertation
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File download under embargo until 21 August 2031 | 2025-05-16 13:36:50 -0400 | File download under embargo until 21 August 2031 |
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