脳から快楽と苦痛を読み取る(Reading Pleasure and Pain from the Brain)

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2024-06-11 韓国基礎科学研究院(IBS)

脳から快楽と苦痛を読み取る(Reading Pleasure and Pain from the Brain)Figure 1. Overview of the fMRI experiment
Left: Fluids were delivered using an MR-compatible fluid delivery system (gustometer) and removed from participants’ mouths during the experiment using a suction device.
Middle: Capsaicin or chocolate fluid was delivered twice during the scan, with a duration of 1.5 minutes each for capsaicin fluid and a duration of 3 minutes each for chocolate fluid. The entire run lasted 14.5 minutes.
Right: Participants continuously rated pleasantness or unpleasantness (purple: pain, yellow: pleasure) while receiving capsaicin and chocolate (n = 58).

基礎科学研究所(IBS)のLEE Soo AhnとWOO Choong-Wan率いる研究チームは、ソウル大学とダートマス大学との共同研究で、脳が持続的な痛みと快楽の感情情報をどのように処理するかを明らかにしました。fMRIを用いてカプサイシンとチョコレート液体による持続的な痛みと快楽の際の脳活動を記録し、機械学習技術を用いて快・不快感とその強度をエンコードする脳活動パターンを解明しました。58名の参加者のデータを分析し、痛みと快楽が同じ感情情報を共有し、これが複数の脳領域で表現されることを示しました。これにより、慢性痛患者に共通するうつ病の理解にも貢献することが期待されています。

<関連情報>

快楽と苦痛の持続における情動価や強度の脳内表現 Brain representations of affective valence and intensity in sustained pleasure and pain

Soo Ahn Lee, Jae-Joong Lee, Jisoo Han, +2, and Choong-Wan Woo
Proceedings of the National Academy of Sciences  Published:June 10, 2024
DOI:https://doi.org/10.1073/pnas.2310433121

Significance

Pleasure and pain, as fundamental emotional experiences, possess shared general affective dimensions such as positive vs. negative (i.e., affective valence) or weak vs. strong (i.e., affective intensity). The understanding of how these common affective dimensions across pleasure and pain are encoded in the brain carries significant clinical implications, particularly concerning pleasure-induced analgesia or anhedonia comorbid with chronic pain. Here, we identified brain representations of affective intensity and valence shared across pleasure and pain. These two representations were not only spatially nonoverlapping with each other but also functionally connected to distinct large-scale brain networks. Our findings support the existence of the modality-general affective coding in the brain, integrating distinct sensory information of pleasure and pain into general affective experiences.

Abstract

Pleasure and pain are two fundamental, intertwined aspects of human emotions. Pleasurable sensations can reduce subjective feelings of pain and vice versa, and we often perceive the termination of pain as pleasant and the absence of pleasure as unpleasant. This implies the existence of brain systems that integrate them into modality-general representations of affective experiences. Here, we examined representations of affective valence and intensity in an functional MRI (fMRI) study (n = 58) of sustained pleasure and pain. We found that the distinct subpopulations of voxels within the ventromedial and lateral prefrontal cortices, the orbitofrontal cortex, the anterior insula, and the amygdala were involved in decoding affective valence versus intensity. Affective valence and intensity predictive models showed significant decoding performance in an independent test dataset (n = 62). These models were differentially connected to distinct large-scale brain networks—the intensity model to the ventral attention network and the valence model to the limbic and default mode networks. Overall, this study identified the brain representations of affective valence and intensity across pleasure and pain, promoting a systems-level understanding of human affective experiences.

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