Production of Emotions Conveyed by Voice in Parkinson’s Disease: Association Between Variability of Fundamental Frequency and Gray Matter Volumes of Regions Involved in Emotional Prosody

Objective: Parkinson's disease (PD) is associated with impairment in producing emotions conveyed by voice which could depend on motor limitations of the vocal apparatus and/or alterations in emotional processing. This study explores the relationship between the standard deviation of fundamental frequency (F0SD) of emotional speech and the volume of specific gray matter regions. Method: Fifteen PD patients and 15 healthy controls (HC) were asked to produce different emotions vocally elicited by reading short stories. For each vocal track, the F0SD was calculated as index of variability. All subjects underwent a structural magnetic resonance imaging and a voxel-based morphometry analysis. An ad hoc mask of brain regions implicated in emotional prosody was constructed to test the relationship between F0SD and the level of brain atrophy. Results: PD patients showed lower F0SD values than HC in the expression of anger. Neuroimaging results showed brain atrophy in PD patients in a widespread bilateral network, including frontal areas, left cingulate cortex, parietal areas as well as occipital cortices. In the PD group, a positive correlation was observed between F0SD values of anger and volumes of the bilateral supramarginal gyrus, left thalamus, right inferior frontal gyrus, and amygdala. Conclusions: The lower F0SD values observed in PD patients in anger production are consistent with their lower ability to express anger effectively through voice compared to HC. Our data demonstrated the involvement of right-lateralized areas, such as the inferior frontal gyrus and amygdala, which are typically involved in emotional prosody. Disturbances in emotion processing might contribute to speech production deficits in PD, probably in addition to the motor impairment of the articulatory system.