Exploring Facial Expression Recognition in Parkinson’s

Parkinson’s is a neurodegenerative condition and some studies have suggested that people with Parkinson’s (PwP) experience difficulties with recognising facial expressions. Previous studies, however, have focussed on static stimuli, as opposed to “dynamic” (moving) displays. Furthermore, the handful of studies that have used dynamic expressions, have not offered mechanistic explanations of why PwP would experience difficulties. Here we used a novel task of emotion recognition from dynamic stimuli which provides mechanistic insights by quantifying the extent to which people rely on kinematic signals versus spatial cues. 18 PwP and 17 controls completed the Point Light Faces (PLF) task. On each trial participants viewed PLFs that varied in emotion (angry, happy, sad), level of spatial exaggeration (50%, 100%, 150%) and speed (50%, 100%, 150%); participants rated how angry, happy and sad the PLFs appeared. An emotion recognition accuracy score was calculated as the mean rating of the two incorrect emotions subtracted from the rating for the correct emotion. PwP performed this before taking their medication in the morning. A 2x3x3x3 ANOVA was performed to analyse the effect of group, emotion, spatial and kinematic levels on emotion recognition accuracy. There were no significant interactions between spatial level and group, or kinematic level and group [p>0.05], suggesting that compared to controls, PwP are equally affected by speeding up or spatially exaggerating emotional displays. Nevertheless, an emotion by group interaction [F(1.57,51.84)=5.25, p=0.013, ηP2=0.14] revealed that, compared to controls, PwP had significantly lower accuracy for happy [t(33)=2.32, p=0.013, mean difference = -1.48], but not angry or sad expressions [p>0.05]. These results suggest that there are no meaningful differences between PwP and controls in terms of their reliance on kinematic and spatial cues. However, PwP may experience challenges with recognising positive emotions, such as happiness. Future work will interrogate why PwP would struggle with positive emotions.