Acoustic Analysis of Intonation in Persons With Parkinson's Disease Receiving Transcranial Magnetic Stimulation and Intensive Voice Treatment

Abstract

Intonation is one of the prosodic features manifested acoustically in the fundamental frequency (f0). Intonation abnormality is common and prominent in the speech of persons with Parkinson's disease (PD). The current research investigated acoustically five intonational features including f0 declination, f0 resetting, sentence stress, terminal fall, and syntactic prejunctural fall in 20 PD participants, receiving Lee Silverman Voice Treatment (LSVT)-LOUD alone, or combined with transcranial magnetic stimulation delivered to the left or right primary laryngeal motor cortex. The results revealed that f0 declination, sentence stress, and terminal fall changed significantly from pre- to post-treatment, and the changes of declination and terminal fall were maintained at the follow-up evaluations. The observed changes in intonation were attributed to LSVT alone, which caused large changes of f0 magnitude. f0 resetting and syntactic prejunctural fall did not change significantly following treatment, probably because these intonational features need very precise fine motor control of the intrinsic laryngeal muscles to make small-range, rapid f0 adjustments, which were not improved by LSVT in the present PD participants. Difficulties with syntactic processing previously reported in PD may have also contributed to the lack of improvement in resetting and prejunctural fall, since these f0 features are used to mark syntactic boundaries within utterances.