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Pharmaceutical and neurosurgical treatments reliably ameliorate the cardinal motor symptoms in PD but, they often yield inconsistent outcomes for speech and voice disorders, with some studies showing exacerbation of pre-treatment deficits. Therefore, it is crucial to develop and optimize novel approaches that could simultaneously improve speech and voice deficits in PD and facilitate existing behavioral interventions. This project will investigate the immediate and short-term effects of multiple sessions of HD-tDCS over the left SMA on speech and voice deficits in PD.
Parkinson's disease (PD) is a movement disorder that affects more than one million individuals in the United States. Over 90 percent of individuals with PD manifest speech and voice impairments in the course of their disease, which can significantly compromise patients' quality of life. While pharmaceutical intervention and deep brain stimulation reliably improve the cardinal motor symptoms of PD, such as tremor, rigidity, and bradykinesia, the effects of these treatments on speech and voice are inconsistent, with some studies showing the exacerbation of pre-treatment deficits. This inconsistency often occurs because treatments are calibrated to ameliorate limb motor symptoms, with no direct optimization to improve speech and voice functions. However, there is no established non-invasive neurostimulation protocol for communication disorders in PD. Increasing evidence supports the application of non-invasive brain stimulation techniques such as transcranial direct current stimulation (tDCS) to improve both motor and non-motor symptoms in PD. However, limited evidence exists regarding the application of tDCS to improve speech and voice disorders in PD. Moreover, there is no established long-term effect of tDCS on speech and voice deficits in PD. In this proposed study, we will address these gaps by investigating the immediate and short-term effects of high definition-transcranial direct current stimulation (HD-tDCS) over the left supplementary motor area (SMA) on speech and voice deficits in 24 PD and 24 matched control participants.
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| Label | Type | Description | Intervention Names |
|---|---|---|---|
| Active high definition transcranial direct current stimulation (HD-tDCS) | Experimental | High-definition anodal transcranial direct current stimulation (2 milliamps [mA]) for 5 consecutive days (one session per day for 20 minutes each). The electrical current will be administered over the left Supplementary motor area. The stimulation will be delivered at an intensity of 2 milliamps (mA) for a maximum of 20 minutes. |
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| Sham high definition transcranial direct current stimulation (HD-tDCS) | Experimental | High-definition sham transcranial direct current stimulation (2 milliamps [mA]) for 5 consecutive days (one session per day for 20 minutes each). The electrical current will be administered over the left Supplementary motor area. The current will be ramped up for the first 30 seconds following which the intensity will drop to 0 milliamps (mA). |
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| Name | Type | Description | Arm Group Labels | Other Names |
|---|---|---|---|---|
| Active transcranial direct current stimulation | Device | HD electrodes (diameter of 1.2 cm) will be placed on the participants' skull using an HD-tDCS cap (Soterix Medical Inc. New York) and based on 5-10 international montage. Active stimulations will be delivered by a 9 MxN Soterix HD-tES device for 20 minutes( 2 mA) per day for 5 days. |
| Measure | Description | Time Frame |
|---|---|---|
| Voice loudness measures | Acoustics measures of voice loudness including voice intensity (dB), shimmer (Cycle-to-cycle voice intensity perturbation) and smoothed cepstral peak prominence will be calculated for each participant. | Acoustic measures related to voice loudness will be measured at baseline, immediately after the last session of stimulation, one week and one month after the las stimulation session. |
| Fundamental frequency measures | Changes in the accuracy rate (percentage of correct repetitions) of non-word repetition | Fundamental frequency (F0), jitter (Cycle-to-cycle voice F0 perturbation) and harmonic to noise ration will be calculated for each participant. |
| Accuracy of syllable repetition | The number of syllables that correctly produced during syllable repetition task will be calculated for each participant. | Accuracy rate for syllable repetition will be measured at baseline, immediately after the last session of stimulation, one week and one month after the las stimulation session. |
| Speech rate | The speech rate ( number of syllables per second) will be calculated during a syllable repetition task for each participant. | Speech rate will be measured at baseline, immediately after the last session of stimulation, one week and one month after the las stimulation session. |
| Speech rate stability | Variability in speech rate across trials for each syllable length ( 1, 2, and 3 ) will be calculated for each participant. | Speech rate stability will be measured at baseline, immediately after the last session of stimulation, one week and one month after the las stimulation session. |
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Inclusion Criteria:
Exclusion Criteria :
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| Name | Role | Phone | Extension | |
|---|---|---|---|---|
| Karim Johari | Contact | 225-578-3934 | karimjohari@lsu.edu |
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Participants' data are confidential. de-identified data will be publicly available after final analysis.
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| ID | Term |
|---|---|
| D010300 | Parkinson Disease |
| D013060 | Speech |
| ID | Term |
|---|---|
| D020734 | Parkinsonian Disorders |
| D001480 | Basal Ganglia Diseases |
| D001927 | Brain Diseases |
| D002493 | Central Nervous System Diseases |
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| Sham transcranial direct current stimulation | Device | HD electrodes (diameter of 1.2 cm) will be placed on the participants' skull using an HD-tDCS cap (Soterix Medical Inc. New York) and based on 5-10 international montage. Sham stimulations will be delivered by a 9 MxN Soterix HD-tES device. In the sham tDCS condition, the current is only on for 30 seconds before it is ramped back down to 0 milliamps (mA), although the electrodes are still worn for 20 minutes. |
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| D009422 | Nervous System Diseases |
| D009069 | Movement Disorders |
| D000080874 | Synucleinopathies |
| D019636 | Neurodegenerative Diseases |
| D014705 | Verbal Behavior |
| D003142 | Communication |
| D001519 | Behavior |