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Motor instability in parkinsonian speech intensity
A K Ho1, R Iansek, J L Bradshaw
1Psychology Department, Monash University, Clayton, Victoria, Australia. akh26@cam.ac.uk
Summary
Parkinson disease patients exhibit greater speech intensity decay during sustained vowels and reading tasks, indicating motor instability in their speech. This supports a common frontostriatal deficit affecting speech and limb control.
Area of Science:
- Neurology
- Speech-Language Pathology
- Motor Control
Background:
- Parkinsonian speech is often characterized by fading intensity.
- This phenomenon is analogous to motor deficits seen in handwriting and gait.
- Speech intensity instability in Parkinson disease (PD) lacks controlled experimental investigation.
Purpose of the Study:
- To investigate progressive speech intensity decay in Parkinson disease.
- To compare speech intensity decay between PD patients and controls across two tasks.
Main Methods:
- Experiment 1: Sustained vowel phonation in 13 PD patients and controls.
- Experiment 2: Sentence reading in 6 PD patients and controls.
- Measurement of intensity declination over a breath span after maximal inhalation.
Main Results:
- PD patients showed significantly greater progressive intensity decay than controls in both tasks.
- This confirms motor instability within the speech motor system in PD.
- Fading speech is a quantifiable characteristic of Parkinson disease.
Conclusions:
- A common deficit in the frontostriatal circuit affects force control in complex motor sequences.
- This deficit impacts both speech and limb movements in Parkinson disease.
- Findings suggest a unified motor control impairment in PD.