Objective: To investigate acute effects of repetitive transcranial magnetic stimulation (rTMS) of the motor and auditory feedback area on hypokinetic dysarthria in Parkinson’s disease (PD) using acoustic analysis.

Background: PD speech disorders result from basal ganglia deficiency and abnormal auditory-motor integration. rTMS may induce distinct changes in neural plasticity and function.

Methods: Altogether 15 PD patients (age 68.26 ± 5.05 years, disease duration 7.2 ± 4.93 years) with hypokinetic dysarthria participated in the study. Both high-frequency stimulation (10 Hz, 2,250 pulses per session) and low-frequency stimulation (1 Hz, 1,800 pulses per session) were utilized over the right superior temporal gyrus (STG) and vertex regions while only 10 Hz stimulation was used for the orofacial primary motor area stimulation (Eliasova et al., 2013). We used a crossover design with stimulation sites and protocols randomized across subjects and sessions. Functional MRI (3T MR scanner) was performed prior to and immediately after the stimulation and it was used as a readout of stimulation aftereffects. The speech was recorded inside the scanner using an fMRI speech protocol, acoustic analysis of recorded data was performed off-line.

Results: High-frequency stimulation over the STG induced a significant increase of the range of the first formant (p = 0.044) while low-frequency stimulation led to a significant increase of the total pause time. These changes were accompanied by increased functional connectivity of the stimulated region with the right inferior parietal lobule, and the the parahippocampal gyrus, respectively. A significant correlation was found between activation changes of the stimulated area and changes in standard deviation of the second formant (R = 0.654, p = 0.029).

Conclusions: Modulation of the auditory feedback area by rTMS may lead to motor-speech improvement through manipulation of auditory-motor and non-motor connections.

References: Eliasova I, Mekyska J, Kostalova M, Marecek R, Smekal Z, Rektorova I. Acoustic evaluation of short-term effects of repetitive transcranial magnetic stimulation on motor aspects of speech in Parkinson’s disease. J Neural Transm 2013;120:597–605.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/effects-of-non-invasive-brain-stimulation-on-motor-speech-disorders-in-parkinsons-disease/