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Author ORCID Identifier


Open Access Dissertation

Document Type


Degree Name

Doctor of Philosophy (PhD)

Degree Program


Year Degree Awarded


Month Degree Awarded


First Advisor

Youngbin Kwak

Subject Categories

Cognitive Psychology | Developmental Psychology | Experimental Analysis of Behavior


In the neuroscience of economic decision making, the brain’s motor system has been ascribed a role in implementing choice actions. However, recent work has revealed canonical motor signals much in advance of choice action, possibly indicating their role in evaluation of decision options. In the current dissertation, we applied multimodal neuroimaging combining EEG and fMRI and used a novel paradigm that temporally separated the evaluation phase from the action phase of a decision-making process to investigate the mechanisms through which the motor control system contributes to decision making. Additionally, we further examined the developmental changes during the two phases of decision making.

In Chapter 2, we examined trial-to-trial covariations of concurrently recorded EEG and fMRI to determine whether or not the motor system communicates with the valuation system while evaluating decision options. The results demonstrated the engagement of cortical motor signal (sensorimotor beta desynchronization) during evaluation of decision options, replicating our previous study. This neural signal recruited the cortico-basal ganglia-thalamic circuitry of motor control as identified from EEG-fMRI covariation. Furthermore, the identified brain regions from the motor control circuitry showed evidence of encoding reward and risk information. Importantly, the engagement of motor system happened without involving the valuation system, as shown by no evidence of direct communication.

In Chapter 3, we examined the differences in behavioral sensitivity to reward and risk information from early adolescents to adulthood with 97 participants aged 10-27 yrs and further determined what mental process drives these developmental changes by comparing the neural signals along the decision-making cascade, specifically the sensorimotor beta during evaluation and action phases, and mediofrontal theta during action phase. Behaviorally, the influence of risk and reward were more prominent in younger age, which decreased with age. At the neural level, evaluation-phase sensorimotor beta showed significant dissociation of reward and risk levels only in adults (aged 21 and above) but not in younger age (10-20 yrs), suggesting the less efficiency in distinguishing and encoding the related reward or risk information in adolescents compared to adults. The mediofrontal theta and the strength of RT-theta correlation in action phase, which reflected adaptive cognitive control, showed an inverted-U developmental pattern with the peak around early adulthood. Collectively, these results suggest that decreased sensitivity to reward and risk information across age may result from adaptive cognitive control that develops with age.

Taken together, the current investigations demonstrate the unique contribution of motor system in decision making and extend the prior literature about neural developmental changes in different stages over decision making process.