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Access Type

Open Access Thesis

Document Type


Degree Program


Degree Type

Master of Science (M.S.)

Year Degree Awarded


Month Degree Awarded



Choosing a course of action in our daily lives requires an accurate assessment of the associated risks as well as the potential rewards. The present two studies investigated the mechanism of how reward and risk level influence the motor decisions of speeded actions (Chapter 2) and its neural dynamics (Chapter 3) by focusing on the beta band (15-30 Hz) oscillation patterns reflected in the EEG signals. Participants performed a modified version of the Go-NoGo task, in which they earned reward points based on the speed and accuracy of response. On each trial, the reward points at stake (120 vs. 6) and the probability that a Go signal would follow (Go-probability) were presented prior to a Go/NoGo signal (Trial Information Period). The behavioral results (from both Chapters 2 and 3) showed that larger amount of rewards can motivate people to respond faster, and this effect was modulated by the assessed risk, suggesting that decisions for actions are based on a systematic trade-off between rewards and risks. The EEG data showed that motor beta oscillations from the two studied brain regions reflected different levels of motivation towards a motor response across different reward and risk levels. Specifically, the lower beta power associated with higher reward and lower risk level. Collectively, the results provide a mechanistic understanding of how motivational cues are translated into action outcomes via modulating patterns of brain oscillations.


First Advisor

Youngbin Kwak