Enhanced Activation in the Left Anterior Insula Induced by Reward Cues

764 

Abstract Submission 

Yasunori Kotani¹, Yoshimi Ohgami¹, Hajime Kageyama², Nobukiyo Yoshida³, Hiroyuki Akai², Akira Kunimatsu⁴, Shigeru Kiryu⁵, Yusuke Inoue⁶

¹Tokyo Institute of Technology, 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

Yasunori Kotani  
Tokyo Institute of Technology
Meguro, Tokyo

Yoshimi Ohgami  
Tokyo Institute of Technology
Meguro, Tokyo

Hajime Kageyama  
The University of Tokyo
Minato, Tokyo

Nobukiyo Yoshida  
Niigata University of Health and Welfare
Niigata, Niigata

Hiroyuki Akai  
The University of Tokyo
Minato, Tokyo

Akira Kunimatsu  
International University of Health and Welfare
Minato, Tokyo

Shigeru Kiryu  
International University of Health and Welfare
Narita, Chiba

Yusuke Inoue  
Kitasato University
Sagamihara, Kanagawa

The stimulus-preceding negativity (SPN) is an event-related potential reflecting anticipation of a salient stimulus. Previous studies propose the anterior insula (aINS) as a source of the SPN. A shared characteristic of the SPN and aINS is the right hemisphere dominance. However, some reports indicate that the right hemisphere dominance of the SPN diminishes when recorded before a reward-related stimulus due to increased left hemisphere activity triggered by reward (Ohgami et al., 2006). If the aINS is the source of the SPN, activation in the left aINS should be increased by a reward-related stimulus, and the aINS should exhibit no hemisphere difference. In the present fMRI study, we investigated whether the right hemisphere dominance of the aINS would be diminished by the presentation of a reward-related stimulus. Additionally, we manipulated the content of the reward-related stimulus (reward cue and reward outcome). The reward cue informed participants about the possibility of receiving a monetary reward, initiating the reward anticipation process. The reward outcome stimulus provided information about the actual amount of monetary reward received, triggering the reward consumption process. There is a possibility that the right hemisphere dominance of the aINS could change between the cue and the outcome because the two stimuli elicit distinct brain activation patterns (Zen et al., 2022). We assume that the right hemisphere dominance of the aINS could be diminished by the reward cue because the aINS is involved in anticipation of salient stimuli (Ohgami et al., 2023).

Participants included 31 healthy adults. They performed a time estimation task, where they were instructed to press a button when they believed that a specified time (3, 5, or 7 seconds) had passed. Following the button press, a reward cue stimulus (Cue) was presented, indicating whether they could receive a monetary reward (RW condition) or not (NR condition) in the current trial. A few seconds after the Cue, a reward outcome stimulus (Outcome) displayed the amount of reward received (100 JPY in the RW and 0 JPY in the NR). Regressors were set at onsets of cue and outcome stimuli, and four fMRI images at the Cue and the Outcome in the two conditions were generated (RW/Cue, NR/Cue, RW/Outcome, and NR/Outcome). Beta values were extracted from the left and right aINS, and the values in the four images were separately subjected to repeated-measures analyses of variance (ANOVA) with Hemisphere (left/right) as a factor to assess the right hemisphere dominance of the aINS.

Significant activations were observed in the bilateral aINS in the RW/Cue, NR/Cue, and RW/Outcome. In the NR/Outcome, only the activation in the right aINS reached significance. ANOVAs indicated no right hemisphere dominance in the RW/Cue, while significant right hemisphere dominance was observed in the other three conditions (NR/Cue, RW/Outcome, and NR/Outcome). We also compared the beta value in the left aINS between the RW/Cue and NR/Cue. The analysis revealed that the left aINS in the RW/Cue showed greater activation than in the NR/Cue.

The approach-withdrawal theory (Davidson & Irwin, 1999) suggests that positive information is predominantly processed in the left hemisphere, while negative information is predominantly processed in the right hemisphere. This could explain the increased activation in the left aINS in response to reward information. The present study demonstrates that the activation in the left aINS was heightened by the reward cue stimulus, which provides information about a potential future monetary reward. The aINS functions as a gatekeeper of information flow, and this region initiates activation before salient stimuli (Ohgami et al., 2023). The preparatory activation in the aINS may explain why increased activation in the left aINS was observed at the reward anticipation stage rather than at the reward consumption stage.

Reward and Punishment ¹

Attention: Visual ²

Cognition

Electroencephaolography (EEG)

FUNCTIONAL MRI