Summary: The study titled: “The Role of Prefrontal Inhibition in Regulating Fascial Expression of Pain.”, examines the role of pre frontal cortex in the control of fascial expression of pain (Karmann et al.). Expression of pain is determined by a certain factor in the environment (like the availability of caregiver) and also on factors that exist within an individual. Expressing pain is a form of communicating once feelings to others. Understanding expressions may help in assessing the pain in a patient (Craig). Presently, assessment of pain in an individual, is done based on the verbalization of pain by the patient. It would be interesting to know how the brain controls facial expression of real pain, and thus, this study is important. The study will also help improve once understanding about the mechanism of expressing pain. The stimulation of the median prefrontal cortex of healthy subjects, was associated with the inhibition in the expression of pain. The prefrontal cortex was stimulated using low frequency repetitive transcranial magnetic stimulation. This stimulation can help lower excitability of the median prefrontal cortex and inhibits facial expression of pain. However, the stimulation of median prefrontal cortex, did not alter the experience of pain in the subjects.
Back Ground and Perspective: Facial expressions, helps people perceive pain felt by others. Previous imaging studies by Karmann and a group of researchers, helped identify the role of motor inhibition and median prefrontal cortex in the facial expression of pain (Karmann et al.). Early studies on this subject, did not determine the area of the pre-frontal cortex that inhibited facial expression. The median prefrontal cortex is important in regulating emotional behavior of the individual (Spielberg et al.). It also serves other functions like autonomic and endocrine regulation (Guhn et al.). Understanding nonverbal communication of pain, can help add credibility to the expression of pain made by verbal communication. It is particularly important in dementia patient who will have difficulty in verbalizing their pain (Craig). In the present study, researchers have used transcranial magnetic stimulation to attenuate excitability in the targeted area, to study the changes in facial expression and pain perception.
Method and Result: Thirty-six (male =16 and female = 20) healthy subjects participated in the study. The study was approved by the Ethic Committee of the Institute and a written consent was obtained from each subject. Monetary compensation was also provided. The authors have taken care to mention all required details in the methodology. The information provided is sufficient for researchers who want to repeat the information. There were two sessions in the experimental protocol. All participants had to participate in both the session. The first session was for training purpose and to accustom the subjects to the procedures. The actual measurements were made during the second session.
Each participant received two stimuli: a repetitive transcranial magnetic stimulation and a sham stimulus, at the region of the median prefrontal cortex region of the skull. There was a 1-week gap between the two types of stimuli. The order of stimuli, for the participants was done in a random fashion. The researchers have taken care to reduce the bias that may arise in the study. Immediately following stimuli, the participants were assessed for facial expression of pain. The assessment of facial expression of pain was done by first video-recording the facial expression, and the facial expression was coded using the Facial Action Coding system. The pain stimuli were induced using a short acting thermal and pressure stimuli. Following the assessment experiment, the participants were asked to grade their pain perception by filling a Situational Catastrophizing Questionnaire (SCQ). Facial behavior and pain perception were scored on a subjective scale. ANOVA was used to study the within subject and between subject variance. T- test was used to analyze the significance between dependent samples. SPSS version 22 (IBM Crop) software was used for the statistical analysis.
Discussion and Conclusion: The result is discussed in the light of existing knowledge and based on the research findings. The study identified that reducing the excitability of the median prefrontal cortex, improved facial expression of pain. The role of prefrontal cortex in emotion and facial expression, is already known. This study, has helped make a significant addition to the existing knowledge on the subject. Median region of the prefrontal cortex is involved in motor inhibition. Human, like other animals, have an innate ability to express the pain they feel on their face. Studies suggest that this expression of pain on the face is not reflexive, but driven by stimuli when the person is a child. As the child grows, he learns to suppress his pain, so as to adjust to the society. The ability to suppress facial expression of pain is largely acquired. The authors, in the light of their findings, suggest that low frequency transcranial magnetic stimulation, can help overcome the acquired inhibition and enable the innate ability of the subject to express pain facially. Inhibiting median prefrontal cortex can only affect the expression of pain experience, but does not affect the intensity of pain experienced nor the emotional appraisal of pain. Thus, the inhibitory effect of prefrontal cortex is not by decreasing painful experience. I agree with their discussion.
Work Cited:
Craig, Kenneth D. "The Facial Expression of Pain Better Than a Thousand Words?". APS Journal 1.3 (1992): 153-162. Web. 27 Mar. 2016.
Deyo, Kathleen S., Kenneth M. Prkachin, and Susan R. Mercer. "Development of Sensitivity to Facial Expression of Pain". Pain 107.1 (2004): 16-21. Web.
Guhn, Anne et al. "Medial Prefrontal Cortex Stimulation Modulates the Processing of Conditioned Fear". Front. Behav. Neurosci. 8 (2014): n. pag. Web.
Karmann, Anna Julia et al. "The Role of Prefrontal Inhibition in Regulating Facial Expressions of Pain: A Repetitive Transcranial Magnetic Stimulation Study". The Journal of Pain 17.3 (2016): 383-391. Web.
Langford, Dale J et al. "Coding of Facial Expressions of Pain in The Laboratory Mouse". Nature Methods 7.6 (2010): 447-449. Web. 27 Mar. 2016.
Spielberg, Jeffrey M. et al. "Prefrontal Cortex, Emotion, And Approach/Withdrawal Motivation". Social Pers Psych Compass 2.1 (2008): 135-153. Web. 7 Apr. 2016.
