Emotional facedness in Parkinson’s disease

People with Parkinson’s disease (PD) have a deficit of facial expression. Previous studies indicate that hemispheric dominance for emotional processing can give rise to an asymmetric pattern of facial expression of emotion. In this study, we aimed to evaluate possible asymmetry in facial emotion expressivity in PD. Twenty PD patients and twenty healthy controls were video-recorded while posing the 6 basic emotions. The most expressive pictures were derived from the videos and chimeric faces were created. Nine healthy raters were asked to judge which of the two chimeras looked more expressive. Chosen responses, reaction times and confidence levels were the main outcome measures. We evaluated possible differences in these measures within each group and between groups (PD, healthy controls). We assessed possible correlations between a global facial laterality index (pooling all emotions together) as well as facial laterality indexes for each emotion and the body laterality index, accounting for the predominant side of limb bradykinesia in patients. There was no difference in outcome measures when evaluating the two hemifaces within PD patients and healthy controls or between the two groups (all Ps > 0.05). In PD patients there was a correlation between the global facial laterality index and the body laterality index (R = − 0.39, P = 0.01), suggesting that the most expressive hemiface corresponded to the less affected body side. The results of our study do not support the hypothesis of hemisphere predominance in regulating facial emotion expressions and provides novel information on altered facial emotion expression in PD.