Date of Award

2017

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Graduate Group

Neuroscience

First Advisor

Joseph W. Kable

Abstract

Humans often make decisions that involve tradeoffs between immediate and delayed consequences, and tend to devalue or discount future outcomes. This phenomenon, known as delay discounting, has several real-world implications. A high discounter, indicating more impulsive behavior, is more likely to engage in risky behavior such as smoking or gambling, while a low discounter, exhibiting more patient behavior, is more likely to attain better educational and financial outcomes. Recent studies demonstrate that under certain conditions, imagining the future reduces discounting. The goal of this thesis is to examine the cognitive role and neural basis of imagination during intertemporal choice, and investigate the mechanisms by which imagination influences decision-making. Chapter 2 examines how specific components of imagination modulate activity in specific nodes of the default mode network. We find that two components of imagination, construction and evaluation, distinctly activate the dorsal and ventral nodes of the default mode network, demonstrating separate modifiability and indicating a role for multiple processes underlying imagination. Chapter 3 extends this finding by examining activity in these nodes while participants are completing a choice task. Since tangibility and value are often confounded in intertemporal choice, we used our neural markers of construction and evaluation from Chapter 2 to disentangle these distinct components during choice. Though we find that activity in evaluative regions increases when individuals choose a delayed option, we also find greater activity in constructive regions when individuals choose a delayed outcome, indicating that chosen options are perhaps imagined more vividly than unchosen ones. Further, greater activity in constructive regions seems to be driven by high discounters, suggesting that higher discounters rely on vividness to a greater extent during choice than lower discounters. We extend this finding in Chapter 4 by investigating the effects of behavioral interventions of the constructive component on delay discounting. Surprisingly, we find that being a better visualizer is correlated with steeper discounting, and long-term training in visualization of personal future goals leads to greater impulsive behavior. Together, these findings advance our understanding of how specific imagination processes influence decision-making through differential neural activity, laying the groundwork for implementing targeted, personally-tailored future interventions to reduce risky behavior.

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