Keeping an eye on pain expression in primary somatosensory cortex

Faculty/Professorship: Physiological Psychology  
Author(s): Kunz, Miriam ; Chen, Jen-I; Rainville, Pierre
Publisher Information: Bamberg : Otto-Friedrich-Universität
Year of publication: 2022
Pages: 10
Source/Other editions: NeuroImage : a journal of brain function, 217 (2020), 10 S. - ISSN: 1095-9572, 1053-8119
is version of: 10.1016/j.neuroimage.2020.116885
Year of first publication: 2020
Language(s): English
Licence: Creative Commons - CC BY-NC-ND - Attribution - NonCommercial - NoDerivatives 4.0 International 
URN: urn:nbn:de:bvb:473-irb-539427
Facial expressions of pain are composed of a subset of pain-indicative muscle movements. Amongst this subset, contracting the muscles surrounding the eyes (orbicularis oculi muscle) is the most frequent response and has been linked specifically to pain intensity, a fundamental aspect of the sensory dimension of pain. To further explore this link, the present study used functional magnetic resonance imaging (fMRI) to test the hypothesis that orbicularis oculi activation during pain reflects the magnitude of brain responses in areas being involved in processing the sensory dimension of pain.

Facial and brain (BOLD) responses to experimentally-induced heat pain applied to the left lower leg were assessed in twenty-two healthy participants after verbal suggestions were given to specifically increase perceived pain intensity and in control conditions involving no suggestion.

Increases in pain intensity produced the expected changes in facial responses characterized by a stronger contraction of the orbicularis oculi muscle. A regression model further demonstrated that stronger increases in orbicularis oculi activity reflected a larger increase in the BOLD response to the noxious stimulus in the leg area of the primary somatosensory cortex (S1) and a larger decrease in medial prefrontal activity consistent with previous finding suggesting disinhibition. Importantly, the positive coupling of orbicularis oculi with S1 activity was not accounted for by changes in other facial muscles.

These results are consistent with the notion that facial expressions of pain differentially encode the multi-dimensional pain experience and reflect, at least partly, the activity of the spino-thalamo-cortical pathway targeting the primary somatosensory cortex.
GND Keywords: Schmerz; Mimik; Neurologie
Keywords: pain, sensory dimension, facial expression, Orbicularis oculi, fMRI
DDC Classification: 610 Medicine & health  
RVK Classification: YI 5793   
Type: Article
Release Date: 13. May 2022

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