Neural correlates of emotional prosody in Parkinson's disease: A systematic review

Parkinson's disease (PD) is a chronic neurodegenerative disorder involving motor, cognitive and affective symptoms. Processing of emotional prosody, namely the modulation of pitch, volume, and frequency in speech conveying emotional nuances, seems to be affected in PD, but its neural mechanisms have not been fully comprehended. To address this issue, the present systematic review searched for the studies which investigated the neural correlates of emotional prosody in PD patients by means of electrophysiological, neuroimaging, and brain stimulation techniques. Studies on deep brain stimulation of the subthalamic nucleus provided conflicting information on the alterations in emotional prosody perception and expression, with some inconsistency about lateralization. Brain recording and imaging techniques revealed associations of perception and expression deficits of emotional prosody with striatal, frontal, and limbic dysfunction. No study adopted non-invasive brain stimulation to assess emotional prosody processing. Future research should incorporate these techniques in experimental settings and use standardised emotional prosody tasks in patients with PD and in control healthy individuals. Clarifying the neural correlates of emotional prosody may enhance understanding of social communication deficits and could be informative for future therapeutic approaches to improve quality of life in patients with PD.