• Etienne Vachon-Presseau, Mathieu Roy, Choong-Wan Woo, Miriam Kunz, Marc-Olivier Martel, Michael J Sullivan, Philip L Jackson, Tor D Wager, and Pierre Rainville.
• aDepartment of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA bDepartment of Psychology, PERFORM Centre, Concordia University, Montreal, QC, Canada cDepartment of Psychology and Neuroscience, University of Colorado, Boulder, Boulder, CO, USA dDepartment of Psychology University of Bamberg, Bamberg, Germany eDepartment of Anesthesiology, Harvard Medical School, Brigham and Women's Hospital Pain Management Center, Chestnut Hill, MA, USA fRecover Injury Research Centre, Faculty of Health and Behavioural Sciences, The University of Queensland gÉcole de psychologie and CIRRIS and CRIUSMQ, Université Laval, QC, Canada hGroupe de recherche sur le système nerveux central (GRSNC) and Centre de recherche de l'Institut universitaire de gériatrie de Montréal (CRIUGM), Montréal, QC, Canada iDépartement de stomatologie, Université de Montréal, Montréal, QC, Canada.
• Pain. 2016 Aug 1; 157 (8): 1819-30.

AbstractPain behaviors are shaped by social demands and learning processes, and chronic pain has been previously suggested to affect their meaning. In this study, we combined functional magnetic resonance imaging with in-scanner video recording during thermal pain stimulations and use multilevel mediation analyses to study the brain mediators of pain facial expressions and the perception of pain intensity (self-reports) in healthy individuals and patients with chronic back pain (CBP). Behavioral data showed that the relation between pain expression and pain report was disrupted in CBP. In both patients with CBP and healthy controls, brain activity varying on a trial-by-trial basis with pain facial expressions was mainly located in the primary motor cortex and completely dissociated from the pattern of brain activity varying with pain intensity ratings. Stronger activity was observed in CBP specifically during pain facial expressions in several nonmotor brain regions such as the medial prefrontal cortex, the precuneus, and the medial temporal lobe. In sharp contrast, no moderating effect of chronic pain was observed on brain activity associated with pain intensity ratings. Our results demonstrate that pain facial expressions and pain intensity ratings reflect different aspects of pain processing and support psychosocial models of pain suggesting that distinctive mechanisms are involved in the regulation of pain behaviors in chronic pain.

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