Differential Effects of Disease Duration and Dopaminergic Replacement Therapy on Vocal Emotion Recognition in Asymmetric Parkinson's Disease.

Introduction: Recently, studies have suggested a role of motor symptom asymmetry on impaired emotional recognition abilities in Parkinson's disease with a greater vulnerability in patients with a predominance of left-sided symptoms. However, none of them explored the interaction between motor symptom asymmetry and dopamine replacement therapy in different stages of the disease.

Methodology: We explored the recognition of vocal emotion (i.e., emotional prosody) in 15 newly diagnosed Parkinson's disease patients in the early stages of the disease, 15 patients in the advanced stages of the disease and 15 healthy controls. The early patients were studied in two conditions: ON and OFF dopaminergic replacement therapy and both Parkinson's disease groups (early and advanced) were divided into two subgroups according to the asymmetry of motor symptoms.

Results: The analyses revealed two patterns of results. First, as predicted, we observed a reduction in performance for the recognition of vocal emotions in patients with a predominance of left-sided symptoms as compared to both healthy controls and predominantly right-sided symptom patients. Second, in the early stages of the disease, we observed a deleterious effect of dopatherapy on the recognition of vocal emotions for the patients with left-predominant symptoms, and the inverse pattern (i.e., a positive effect of dopatherapy) for the patients with right-predominant symptoms.

Conclusions: Our results bring to knowledge the differential effects of disease duration, dopaminergic replacement therapy and motor symptom asymmetry on vocal emotion recognition in Parkinson's disease.