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Keeping an eye on pain expression in primary somatosensory cortex
Miriam Kunz1, Jen-I Chen2, Pierre Rainville2
1Department of Medical Psychology and Sociology, University of Augsburg, Germany; Physiological Psychology, University of Bamberg, Germany.
Neuroimage
|May 7, 2020
Summary
Facial expressions, particularly eye muscle contractions (orbicularis oculi), reflect pain intensity. This study found that stronger eye muscle activity correlates with increased brain responses in the primary somatosensory cortex during pain.
Area of Science:
- Neuroscience
- Pain Research
- Psychophysiology
Background:
- Facial expressions convey pain, with eye muscle contraction (orbicularis oculi) linked to pain intensity.
- The sensory dimension of pain is crucial for understanding pain perception.
Purpose of the Study:
- To investigate the relationship between orbicularis oculi muscle activation and brain responses during pain.
- To test if orbicularis oculi activation magnitude reflects brain activity in pain-sensory processing areas.
Main Methods:
- Functional magnetic resonance imaging (fMRI) was used to measure brain activity (BOLD responses).
- Experimentally induced heat pain was applied to the leg in healthy participants.
- Participants received verbal suggestions to alter perceived pain intensity.
Main Results:
- Increased pain intensity led to stronger orbicularis oculi muscle contractions.
- Higher orbicularis oculi activity correlated with increased BOLD responses in the primary somatosensory cortex (S1).
- A decrease in medial prefrontal activity was observed, suggesting disinhibition.
Conclusions:
- Orbicularis oculi muscle activation during pain is coupled with activity in the primary somatosensory cortex.
- Facial expressions of pain, specifically eye muscle movements, encode sensory dimensions of pain.
- These findings support the role of the spino-thalamo-cortical pathway in pain expression.
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