Background and Objectives
Vocal dysfunction in Parkinson’s disease (PD) is believed to occur due to disrupted cortical motor–auditory integration, leading to hypophonia and poor voice quality. Several well-studied treatment options, such as the LSVT and SPEAK-OUT! programs have been developed, primarily focusing on vocal loudness. Semi-occluded vocal tract (SOVT) exercises, as a comprehensive treatment approach, are believed to enhance phonatory control in various aspects, although their underlying neural mechanisms remain unexplored. In this study, we first aimed to evaluate changes that might occur after a series of SOVT exercises in terms of acoustic parameters and brain function using QEEG, and then to identify any potential correlations between these two measures.
Methods
Ten PD patients (5 intervention, 5 control) completed 8 sessions of various SOVT exercises. Patients’ voice samples were recorded before and after the treatment using text reading, simultaneous speech, and vowel prolongation. Resting-state and phonation QEEG were also recorded both before and after the intervention. Absolute and relative power, coherence, and asymmetry indices were analyzed using a 2×2 mixed ANOVA with ANCOVA correction for baseline variability. Additionally, statistical analyses were conducted using independent samples t-tests to evaluate differences in fundamental frequency (F0), shimmer, jitter, harmonic-to-noise ratio (HNR), and mean intensity before and after SOVTE.
Results
SOVT exercises led to a decrease in frontal theta relative power (p = 0.021), an increase in alpha–beta fronto-central coherence (p = 0.017), and an improvement in motor beta absolute power over C3/C4 (p = 0.048). Frontal alpha asymmetry shifted toward left-hemisphere dominance (p = 0.031) in the treatment group. A 0.6 SD reduction in global z-score deviation (p = 0.028) indicated cortical normalization. No significant changes were observed in the HNR and F0. Intensity increased significantly (p = 0.024), while both jitter (p = 0.003) and shimmer (p < 0.001) showed significant reductions after the eighth session. Further analysis of the correlation between QEEG outcomes and acoustic parameters is ongoing.
Conclusion
SOVT exercises likely induce measurable neuroplasticity, improving cortical efficiency and sensorimotor integration for phonation in PD. QEEG metrics support SOVT as a promising neuro-rehabilitative tool for PD voice dysfunction as a treatment option.
More analysis is required to enable us to discuss the changes in voice quality and brain function in more detail.