title: The Role of Prefrontal Inhibition in Regulating Facial Expressions of Pain: A Repetitive Transcranial Magnetic Stimulation Study.
abstract: Although research on facial expressions of pain has a long history, little is known about the cerebral mechanisms regulating these expressions. It has been suggested that the medial prefrontal cortex (mPFC) might be involved in regulating/inhibiting the degree to which pain is facially displayed. To test whether such a prefrontal regulation does indeed take place, we reduced medial prefrontal excitability via repetitive transcranial magnetic stimulation (rTMS) and assessed its effect on facial expressions. In a within-subject design, facial and subjective responses to experimental pain as well as "situational" pain catastrophizing were assessed in 35 healthy participants; once after receiving low-frequency rTMS over the mPFC (1 Hz) and once after sham stimulation. Compared with sham stimulation, rTMS over the mPFC resulted in enhanced facial expressions of pain, whereas self-report and pain catastrophizing did not change. The current data show that reducing medial prefrontal excitability (via low-frequency rTMS) makes individuals facially more expressive to pain. This finding indicates that the mPFC is crucially involved in the inhibition of facial expressions of pain. Because this effect was independent of changes in self-report and pain catastrophizing suggests that this inhibitory mechanism is mainly governing the facial expression and not the underlying experience of pain.
  
  
  CONCLUSIONS
  Using rTMS, it was shown that the mPFC is causally involved in the downregulation or silencing of one's facial expression of pain. This might explain why individuals with low mPFC functioning (eg, patients with dementia) are facially more expressive in response to pain.
authors.affiliation: Department of Physiological Psychology, Otto-Friedrich University Bamberg, Bamberg, Germany. Electronic address: anna.karmann@uni-bamberg.de.
authors.forename: Anna Julia
authors.initials: AJ
authors.lastname: Karmann
authors.affiliation: Department of Neurology, General Hospital Fürth, Fürth, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Maihöfner
authors.affiliation: Department of Physiological Psychology, Otto-Friedrich University Bamberg, Bamberg, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Lautenbacher
authors.affiliation: Department of Psychiatry and Psychotherapy, Friedrich-Alexander University of Erlangen-Nuremberg, Erlangen, Germany.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Sperling
authors.affiliation: Department of Psychiatry and Psychotherapy, Friedrich-Alexander University of Erlangen-Nuremberg, Erlangen, Germany.
authors.forename: Johannes
authors.initials: J
authors.lastname: Kornhuber
authors.affiliation: Department of Physiological Psychology, Otto-Friedrich University Bamberg, Bamberg, Germany; Department of General Practice, Gerontology Section, University Medical Center Groningen, Groningen, Netherlands.
authors.forename: Miriam
authors.initials: M
authors.lastname: Kunz
mesh_terms: D000328:Adult; D058443:Catastrophization; D005149:Facial Expression; D005260:Female; D006358:Hot Temperature; D006801:Humans; D008297:Male; D009433:Neural Inhibition / Q000502:physiology*; D009483:Neuropsychological Tests; D010146:Pain / Q000503:physiopathology* / Q000523:psychology; D010147:Pain Measurement; D010812:Physical Stimulation; D017397:Prefrontal Cortex / Q000503:physiopathology*; D057566:Self Report; D014110:Touch; D050781:Transcranial Magnetic Stimulation / Q000379:methods
keywords: Pain; cerebral regulation; facial expression; inhibition; medial prefrontal cortex