title: Deficits in the Mimicry of Facial Expressions in Parkinson's Disease.
abstract: BACKGROUND
  Humans spontaneously mimic the facial expressions of others, facilitating social interaction. This mimicking behavior may be impaired in individuals with Parkinson's disease, for whom the loss of facial movements is a clinical feature.
  
  
  OBJECTIVE
  To assess the presence of facial mimicry in patients with Parkinson's disease.
  
  
  METHODS
  Twenty-seven non-depressed patients with idiopathic Parkinson's disease and 28 age-matched controls had their facial muscles recorded with electromyography while they observed presentations of calm, happy, sad, angry, and fearful emotions.
  
  
  RESULTS
  Patients exhibited reduced amplitude and delayed onset in the zygomaticus major muscle region (smiling response) following happy presentations (patients M = 0.02, 95% confidence interval [CI] -0.15 to 0.18, controls M = 0.26, CI 0.14 to 0.37, ANOVA, effect size [ES] = 0.18, p < 0.001). Although patients exhibited activation of the corrugator supercilii and medial frontalis (frowning response) following sad and fearful presentations, the frontalis response to sad presentations was attenuated relative to controls (patients M = 0.05, CI -0.08 to 0.18, controls M = 0.21, CI 0.09 to 0.34, ANOVA, ES = 0.07, p = 0.017). The amplitude of patients' zygomaticus activity in response to positive emotions was found to be negatively correlated with response times for ratings of emotional identification, suggesting a motor-behavioral link (r = -0.45, p = 0.02, two-tailed).
  
  
  CONCLUSIONS
  Patients showed decreased mimicry overall, mimicking other peoples' frowns to some extent, but presenting with profoundly weakened and delayed smiles. These findings open a new avenue of inquiry into the "masked face" syndrome of PD.
authors.affiliation: Department of Psychology, Ryerson UniversityToronto, ON, Canada; Department of Computer Science and Information Systems, University of Wisconsin-River FallsWisconsin, WI, USA; Toronto Rehabilitation InstituteToronto, ON, Canada.
authors.forename: Steven R
authors.initials: SR
authors.lastname: Livingstone
authors.affiliation: Department of Psychology, Ryerson University Toronto, ON, Canada.
authors.forename: Esztella
authors.initials: E
authors.lastname: Vezer
authors.affiliation: Department of Psychology, Ryerson University Toronto, ON, Canada.
authors.forename: Lucy M
authors.initials: LM
authors.lastname: McGarry
authors.affiliation: Division of Neurology, Department of Medicine, University of TorontoToronto, ON, Canada; Morton and Gloria Shulman Movement Disorder Centre at The Toronto Western HospitalToronto, ON, Canada.
authors.forename: Anthony E
authors.initials: AE
authors.lastname: Lang
authors.affiliation: Department of Psychology, Ryerson UniversityToronto, ON, Canada; Toronto Rehabilitation InstituteToronto, ON, Canada.
authors.forename: Frank A
authors.initials: FA
authors.lastname: Russo
keywords: Parkinson's disease; emotion; facial bradykinesia; facial expression; facial masking; facial mimicry; hypomimia; rhythm