The intonation-syntax interface in the speech of individuals with Parkinson's disease

This study examined the effect of Parkinson's disease (PD) on the intonational marking of final and nonfinal syntactic boundaries and investigated whether the effect of PD on intonation was sex specific.

Eight women and 8 men with PD and 16 age- and sex-matched control participants read a passage at comfortable pitch, rate, and loudness. Nuclear tones from final and nonfinal syntactic boundaries in clauses and lists were extracted. Measures of fundamental frequency (F0) were made on each tone contour.

Individuals with PD demonstrated impaired differentiation of syntactic boundary finality/nonfinality with contour direction. They produced a lower proportion of falling contours in final boundaries and a higher proportion of falling contours in nonfinal boundaries than did control participants. Although not mediated by syntax, the effect of PD on F0 standard deviation (F0 SD) and pitch range in semitones (PRST) was sex specific. Women with PD produced greater F0 SD and PRST than did men with PD and women without PD. Men with PD produced lower PRST than did men without PD.

Impaired intonational marking of syntactic boundaries likely contributes to dysprosody and reduced communicative effectiveness in PD. The effect of PD on intonation was sex specific. The results are not fully explained by PD-related motor execution impairments.