AUTHOR=Livingstone Steven R. , Vezer Esztella , McGarry Lucy M. , Lang Anthony E. , Russo Frank A. 

TITLE=Deficits in the Mimicry of Facial Expressions in Parkinson's Disease

JOURNAL=Frontiers in Psychology

VOLUME=7

YEAR=2016

URL=https://www.frontiersin.org/journals/psychology/articles/10.3389/fpsyg.2016.00780

DOI=10.3389/fpsyg.2016.00780

ISSN=1664-1078

ABSTRACT=<p><bold>Background:</bold> 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.</p><p><bold>Objective:</bold> To assess the presence of facial mimicry in patients with Parkinson's disease.</p><p><bold>Method:</bold> 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.</p><p><bold>Results:</bold> Patients exhibited reduced amplitude and delayed onset in the zygomaticus major muscle region (smiling response) following happy presentations (patients <italic>M</italic> = 0.02, 95% confidence interval [CI] −0.15 to 0.18, controls <italic>M</italic> = 0.26, CI 0.14 to 0.37, ANOVA, effect size [ES] = 0.18, <italic>p</italic> &lt; 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 <italic>M</italic> = 0.05, CI −0.08 to 0.18, controls <italic>M</italic> = 0.21, CI 0.09 to 0.34, ANOVA, ES = 0.07, <italic>p</italic> = 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 (<italic>r</italic> = –0.45, <italic>p</italic> = 0.02, two-tailed).</p><p><bold>Conclusions:</bold> 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.</p>