Discrimination and recognition of facial expressions of emotion and their links with voluntary control of facial musculature in Parkinson's disease.

OBJECTIVE

To explore perception of facial expressions of emotion and its link with voluntary facial musculature control in Parkinson's disease (PD).

METHOD

We investigated in 2 sets of experiments in PD patients and healthy controls the perceptual ability to discriminate (a) graded intensities of emotional from neutral expressions, (b) graded intensities of the same emotional expressions, (c) full-blown discrepant emotional expressions from 2 similar expressions and the more complex recognition ability to label full-blown emotional expressions. We tested an embodied simulationist account of emotion perception in PD, which predicts a link between the ability to perceive emotional expressions and facial musculature control. We also explored the contribution of the ability to extract facial information (besides emotion) to emotion perception in PD.

RESULTS

Those with PD were, as a group, impaired relative to controls (with large effect sizes) in all measures of discrimination and recognition of emotional expressions, although some patients performed as well as the best performing controls. In support of embodied simulation, discrimination and recognition of emotional expressions correlated positively with voluntary control of facial musculature (after partialing out disease severity and age). Patients were also impaired at extracting information other than emotion from faces, specifically discriminating and recognizing identity from faces (with large effect sizes); identity discrimination correlated positively with emotion discrimination and recognition but not with voluntary facial musculature control (after partialing out disease severity and age).

CONCLUSIONS

The results indicate that impaired sensory and sensorimotor processes, which are a function of disease severity, affect emotion perception in PD.