Summary: Researchers have discovered that the brain processes pain and pleasure through overlapping regions. By analyzing the sustained pain caused by capsaicin and the pleasure caused by chocolate, they identified distinct patterns of brain activity linked to the two experiences.
These results improve our understanding of the brain mechanisms responsible for emotional responses. The study could have implications in the treatment of chronic pain and depression.
Highlights:
- The brain uses overlapping regions to process both pain and pleasure.
- Machine learning identified specific patterns of brain activity for emotional intensity and valence.
- The results could help improve treatments for chronic pain and depression.
Source: Institute of Basic Sciences
A team of researchers led by LEE Soo Ahn and WOO Choong-Wan at the Center for Neuroimaging Research (CNIR) of the Institute of Basic Sciences (IBS), in collaboration with CHOI Myunghwan of Seoul National University and Tor D . WAGER of Dartmouth College, revealed how the brain processes emotional information related to sustained pain and pleasure.
Using functional magnetic resonance imaging (fMRI), the team recorded brain activity while participants experienced sustained pain and pleasure induced by capsaicin and chocolate liquids. Using sophisticated machine learning techniques, they discovered the patterns of brain activity that encode pleasant or unpleasant emotions as well as the magnitude of sustained pain and pleasure.
Although pain and pleasure are opposite experiences, they are intimately linked. Previous studies have suggested a set of brain regions that respond to both pain and pleasure.
However, most previous studies have been conducted on animals rather than humans, and studies directly comparing brain representations of pain and pleasure in the same individuals are still lacking.
In this study, the research team conducted an experiment that induced sustained pain and pleasure in MRI scanner participants, by administering capsaicin and chocolate liquids. While experiencing sustained pain and pleasure, participants reported moment-to-moment changes in their subjective pleasantness and unpleasantness.
Participants’ subjective reports of pleasant and unpleasant aspects gradually increased and persisted during deliveries of capsaicin and chocolate liquids and decreased after deliveries ended. By inducing dynamic changes in sustained pain and pleasure, the team sought to identify brain regions activated by both experiences.
The research team collected brain imaging data and moment-to-moment changes in pleasantness or unpleasantness ratings from 58 participants. The team used machine learning techniques to analyze the brain data and identified a set of brain regions that responded to both sustained pain and pleasure.
Based on the brain activity patterns of these common brain regions, the team developed two predictive models to capture (1) the magnitude of affective experiences, whether pleasant or unpleasant (i.e. “affective intensity”) and (2) the magnitude of pleasantness or unpleasantness (i.e. “affective valence”).
The researchers found that these models successfully predicted the affective intensity and valence information of sustained pleasure and pain, both from the 58 individuals in the training dataset and from 61 new individuals from the independent test dataset.
Activity patterns predictive of affective intensity and valence were spatially distinguishable, and these patterns were connected to distinct functional brain networks.
This suggests that information about affective intensity and valence represents multiple aspects of the brain mechanisms underlying the pain-pleasure interaction.
“Although there have been separate studies on pain and pleasure, research comparing pain and pleasure experiences in the same individuals has rarely been conducted,” said Dr WOO Choong-Wan, associate director of ‘IBS, who led the study. .
“Patterns of brain activity for affective valence and intensity may contribute to the understanding of how pain and pleasure interact, as well as the brain mechanisms underlying depression commonly observed in pain patients chronic.”
LEE Soo Ahn, doctoral student and first author of this study, pointed out: “These results demonstrate that pain and pleasure share the same underlying emotional information about the pleasant and unpleasant side,” adding: “We should focus on the fact that affective valence and intensity information can be represented in multiple brain regions.
About this research news on pleasure, pain and neuroscience
Author: William Suh
Source: Institute of Basic Sciences
Contact: William Suh – Institute for Basic Sciences
Picture: Image is credited to Neuroscience News
Original research: Closed access.
“Brain representations of affective valence and intensity in sustained pleasure and pain” by LEE Soo Ahn et al. PNAS
Abstract
Brain representations of affective valence and intensity in sustained pleasure and pain
Pleasure and pain are two fundamental and closely related aspects of human emotions. Pleasant sensations can reduce subjective sensations of pain and vice versa, and we often perceive the end of pain as pleasant and the absence of pleasure as unpleasant.
This implies the existence of brain systems that integrate them into general modal representations of affective experiences.
Here, we examined representations of affective valence and intensity in a functional MRI (fMRI) study (not = 58) of sustained pleasure and pain.
We found that distinct subpopulations of voxels within the ventromedial and lateral prefrontal cortex, orbitofrontal cortex, anterior insula, and amygdala were involved in intensity-based decoding of affective valence. Predictive models of affective valence and intensity showed significant decoding performance in an independent test dataset (not = 62).
These patterns were differentially connected to distinct large-scale brain networks: the intensity pattern to the ventral attention network and the valence pattern to the limbic and default mode networks.
Overall, this study identified brain representations of the affective valence and intensity of pleasure and pain, thereby promoting a systemic understanding of human affective experiences.