Poster No:
2001
Submission Type:
Abstract Submission
Authors:
Yoshimi Ohgami1, Yasunori Kotani1, Hajime Kageyama2, Nobukiyo Yoshida3, Hiroyuki Akai2, Akira Kunimatsu4, Shigeru Kiryu5, Yusuke Inoue6
Institutions:
1Institute of Science Tokyo, Meguro, Tokyo, 2The University of Tokyo, Minato, Tokyo, 3Niigata University of Health and Welfare, Niigata, Niigata, 4International University of Health and Welfare, Minato, Tokyo, 5International University of Health and Welfare, Narita, Chiba, 6Kitasato University, Sagamihara, Kanagawa
First Author:
Co-Author(s):
Akira Kunimatsu
International University of Health and Welfare
Minato, Tokyo
Shigeru Kiryu
International University of Health and Welfare
Narita, Chiba
Introduction:
There are many reports that indicate that left-hemisphere activity serves as an indicator of the reward system. In addition, recent research on the reward system has reported that engaging in tasks where individuals earn rewards results in greater activation of the reward system compared to situations where rewards are determined automatically by a computer (Harmon-Jones, 2024; Mühlberger, 2017). These studies indicate that the more committed individuals are to their actions, the higher the activation in the reward system.
If commitment influence activity in the reward system, it is reasonable to expect that left-hemisphere activity will also vary depending on the degree of commitment. In this study, we first aimed to confirm whether left-hemisphere activity reflects reward system activity by investigating whether the activity under a reward condition is higher than that under a no-reward condition. Additionally, we manipulated the timing of reward-information presentation to vary the level of commitment to the task (presented before or after a task response) to examine whether increased commitment leads to enhanced left-hemisphere activity. We conducted two fMRI experiments. In Experiment 1, reward information was presented before the task response, while in Experiment 2, reward information was presented after the task response. We assumed that the commitment to the task could be increased after the task response because participants had engaged in the task by responding to a stimulus.
Methods:
Experiment 1 (N = 25): Participants performed a time-estimation task where instruction stimuli indicating the target duration to be estimated (e.g. 3 s) were presented. They were instructed to press a button with their right index finger when they judged that the instructed time had elapsed. Three seconds after the button press, feedback information was presented indicating whether their timing performance was correct. There were two experimental conditions. In the Reward condition, participants received a monetary reward for correct time estimation. In the No-Reward condition, they did not receive any reward. In both conditions, the amount of reward for each trial was presented along with the instruction stimulus, meaning that the reward information was provided before the task response. After fMRI data collection, beta values in the left anterior insula evoked by reward information were extracted. A paired t-test was conducted to compare beta values between the reward and no-reward conditions.
Experiment 2 (N = 31): Participants performed the same time-estimation task used in Experiment 1 while the reward stimulus was presented after the button press to increase participants' commitment to the task. In the analyses, a paired t-test was conducted to compare beta values in the left anterior insula between the reward and no-reward conditions. Additionally, to compare the level of commitment, an unpaired t-test was conducted on the beta values in Experiment 1 and 2 under the reward condition.
Results:
In Experiments 1 and 2, the beta values in the left anterior insula were larger in the reward condition than in the no-reward condition. Furthermore, the beta values after the task response were larger than that before the task response under the reward condition.
Conclusions:
Results of the present study showed that left-hemisphere activity was significantly higher in the reward condition compared to the no-reward condition, suggesting that it reflects reward system activity. Furthermore, the left insula activity was significantly higher when reward information was presented after the response, indicating increased commitment. These findings support prior research suggesting that commitment enhances reward system activity and demonstrate that left-hemisphere activity could serve as an indicator of commitment-driven reward system effects.
Perception, Attention and Motor Behavior:
Attention: Auditory/Tactile/Motor 1
Attention: Visual 2
Keywords:
FUNCTIONAL MRI
Somatosensory
1|2Indicates the priority used for review
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Please indicate below if your study was a "resting state" or "task-activation” study.
Task-activation
Healthy subjects only or patients (note that patient studies may also involve healthy subjects):
Healthy subjects
Was this research conducted in the United States?
No
Were any human subjects research approved by the relevant Institutional Review Board or ethics panel?
NOTE: Any human subjects studies without IRB approval will be automatically rejected.
Yes
Were any animal research approved by the relevant IACUC or other animal research panel?
NOTE: Any animal studies without IACUC approval will be automatically rejected.
Not applicable
Please indicate which methods were used in your research:
Functional MRI
For human MRI, what field strength scanner do you use?
3.0T
Which processing packages did you use for your study?
SPM
Provide references using APA citation style.
Harmon-Jones. (2024). Does effort increase or decrease reward valuation? Considerations from cognitive dissonance theory. Psychophysiology, 61(6).
Mühlberger. (2017). Perceived control increases the reward positivity and stimulus preceding negativity. Psychophysiology, 54(2), 310–322.
No