I spy with my little eye: The detection of changes in emotional faces and the influence of facial feedback in Parkinson disease

Background and purpose: Parkinson disease (PD) is a progressive neurodegenerative disorder that affects the motor system but also involves deficits in emotional processing such as facial emotion recognition. In healthy participants, it has been shown that facial mimicry, the automatic imitation of perceived facial expressions, facilitates the interpretation of the emotional states of our counterpart. In PD patients, recent studies revealed reduced facial mimicry and consequently reduced facial feedback, suggesting that this reduction might contribute to the prominent emotion recognition deficits found in PD. Methods: We investigated the influence of facial mimicry on facial emotion recognition. Twenty PD patients and 20 healthy controls (HCs) underwent a classical facial mimicry manipulation (holding a pen with the lips, teeth, or nondominant hand) while performing an emotional change detection task with faces. Results: As expected, emotion recognition was significantly influenced by facial mimicry manipulation in HCs, further supporting the hypothesis of facial feedback and the related theory of embodied simulation. Importantly, patients with PD, generally and independent from the facial mimicry manipulation, were impaired in their ability to detected emotion changes. Our data further show that PD patients' facial emotional recognition abilities are completely unaffected by mimicry manipulation, suggesting that PD patients cannot profit from an artificial modulation of the already impaired facial feedback. Conclusions: These findings suggest that it is not the hypomimia and the absence of facial feedback per se, but a disruption of the facial feedback loop, that leads to the prominent emotion recognition deficit in PD patients.

Automated summary

This study investigated the influence of facial mimicry on facial emotion recognition. The results showed that the emotional recognition of the control group was affected by facial mimicry manipulation, while Parkinson's disease patients had impairments in their ability to detect emotion changes. Furthermore, the study found that the facial emotion recognition abilities of Parkinson's disease patients were completely unaffected by mimicry manipulation.