Effects of Parkinson's Disease on Fundamental Frequency Variability in Running Speech

Abstract

In Parkinson's Disease (PD), qualitative speech changes such as decreased variation in pitch and loudness are common, but quantitative vocal changes are not well documented. The variability of fundamental frequency (F0) in 32 individuals (23 male) with PD both ON and OFF levodopa medication was compared with 32 age-matched healthy controls (23 male). Participants read a single paragraph and estimates of fundamental frequency (F0) variability were determined for the entire reading passage as well as for the first and last sentences of the passage separately. F0 variability was significantly increased in controls relative to both PD groups and PD patients showed significantly higher F0 variability while ON medication relative to OFF. No significant effect of group was seen in the change in F0 variability from the beginning to the end of the reading passage. Female speakers were found to have higher F0 variability than males. F0 variability was both significantly reduced in PD relative to controls and significantly increased in patients with PD during use of dopaminergic medications. F0 variability changes over the course of reading a paragraph may not be indicative of PD but rather dependent on non-disease factors such as the linguistic characteristics of the text.

Figures

Figure 1

Effects of group (Control, PD OFF medication, PD ON medication) and sex (F: female, M: male) on the standard deviation of the fundamental frequency (F0SD; left upper panel), the semitone standard deviation (STSD; right upper panel), the difference in F0SD between the last and first sentences of the reading passage (ΔF0SD; left lower panel), and the difference in STSD between the last and first sentences of the reading passage (ΔSTSD; right lower panel). Error bars indicate 95% confidence intervals around the mean. Horizontal brackets indicate statistically significant (p < 0.05) differences between groups. All four measures showed a statistically significant effect of sex.