Symptom asymmetry influences how Parkinson’s patients process emotions

New study shows dopamine treatments and symptom asymmetry impact patients differently.

A new study in Neurodegenerative Diseases looks closely at how Parkinson's disease can affect something as everyday and essential as recognizing emotion in someone's voice. The research suggests that both the side of the body most affected by symptoms and the medications used to treat those symptoms may influence how patients interpret vocal emotion.

Researchers from the University of Geneva and Rennes University Hospital studied how people with Parkinson's disease are able to recognize different emotions when hearing speech recordings. Participants were grouped based on whether their physical symptoms were more prominent on the left or right side of the body. The study included individuals in both early and advanced stages of the disease, with early-stage participants tested on and off dopaminergic replacement therapy (DRT).

The results were striking. The authors wrote, "patients with a predominance of left-sided symptoms" had more difficulty recognizing vocal emotions than both healthy controls and patients with right-sided symptoms.

The role of treatment also stood out. In the early-stage group, the researchers found "a deleterious effect of DRT on the recognition of vocal emotions for the patients with left-predominant symptoms, and the inverse pattern (i.e., a positive effect of DRT) for the patients with right-predominant symptoms."

This suggests that the side of symptom onset may affect how DRT interacts with the brain's emotion-processing systems. While the sample size was small, the study points to the value of a more individualized approach to care. As the authors put it, "These results bring to knowledge the differential effects of disease duration, DRT and motor symptom asymmetry on vocal emotion recognition in Parkinson's disease."

"Based on converging results, they propose that asymmetry is a key feature of the disease and should be taken into account at all stages of Parkinson's, especially when evaluating current and future treatment strategies," says Professor Julie Péron, Clinical and Experimental Neuropsychology Laboratory (CENLab), University of Geneva. "The team also emphasizes the importance of replication across independent studies to strengthen the reliability and generalizability of these findings, and to further advance personalized approaches to care."

This research invites us to think beyond movement symptoms and consider how Parkinson's affects communication, connection, and emotional understanding.