Objective: To evaluate the role of the cerebellum in recognizing facial expressions in Parkinson’s Disease (PD) patients.

Background: PD is a neurodegenerative disorder characterized by motor and non-motor features, including emotional-processing impairments, resulting in a difficulty to decode emotions from faces especially for negative emotions [1]. Recognition and discrimination of emotional contents of facial involved a widespread network of cortical and subcortical structures, whereby there is limited evidence about the specific contribution of the cerebellum.

Methods: We enrolled 9 PD patients (aged 42-77; 5 male, 4 female; H&Y range 1-3). We delivered anodal and sham tDCS (2mA, 20 min) over the cerebellum, once a day for 5 consecutive days, in two separate cycles at intervals of at least 1 month. We administered the Facial Emotion Recognition Task at baseline (T0) and after cerebellar tDCS on day five (T1) [2]. Reaction times (RTs) for facial recognition were collected and used as dependent variables.

Results: Anodal cerebellar tDCS significantly enhanced sensory processing in response to negative facial expressions (sadness) by about 16% [(mean±SE) anodal vs sham: -16%±6 vs -3%±5.5; p=0.03] but left positive emotion (happiness) and neutral facial expressions unchanged (p>0.05).

Conclusions: These results show that cerebellar tDCS modulates the way PD patients recognize specific facial expressions thus suggesting that the cerebellum plays a crucial role in recognition of negative emotions. Our study, therefore, corroborates previous knowledge confirming the proposed link between social cognition and the cerebellum. Besides helping to understand the emotional brain processing, the possibility of modulating emotional recognition by cerebellar tDCS in PD patients might be relevant for developing novel therapeutic approaches to improve quality of life as this impairment is associated with heightened interpersonal difficulties.

References: 1. Facial emotion recognition in Parkinson’s disease: A review and new hypotheses. Argaud S, Vérin M, Sauleau P, Grandjean D. Mov Disord. 2018 Feb 23. doi: 10.1002/mds.27305. 2. Cerebellum and processing of negative facial emotions: cerebellar transcranial DC stimulation specifically enhances the emotional recognition of facial anger and sadness. Ferrucci R, Giannicola G, Rosa M, Fumagalli M, Boggio PS, Hallett M, Zago S, Priori A. Cogn Emot. 2012; 26(5): 786–799.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/cerebellar-tdcs-modulates-negative-emotions-recognition-in-parkinsons-disease/