Phonatory characteristics of parkinsonian speech before and after morning medication: the ON and OFF states

A Systematic Review and Bayesian Meta-Analysis of Acoustic Measures of Prosody in Parkinson's Disease

PURPOSE

Linguistic prosody is affected in Parkinson's disease (PD), which implicates the basal ganglia's role in the production of prosody. However, there is no recent systematic synthesis of the available acoustic evidence of prosodic impairment in PD. This study aimed to identify the acoustic features of linguistic prosody that are consistently affected in PD.

METHOD

The authors systematically reviewed articles that reported acoustic features of prosodic production in PD. Articles focused on fundamental frequency (F0) and its variability, intensity and its variability, speech and articulation rate, and pause duration and ratio. From a total of 648 records identified, 36 met criteria for inclusion and exclusion. For each acoustic measurement and task, data from people with PD (PwPD) were compared with those from controls to extract effect sizes. Pooled effect sizes were estimated using robust Bayesian hierarchical regression models.

RESULTS

PD was associated with decreased F0 variability and increased pause duration. There was limited evidence of reduced intensity variability and speech rate in PwPD. No evidence was found to suggest that PD affects articulation rate or pause ratio.

CONCLUSIONS

The primary acoustic parameters of prosody affected by PD are F0 variability and pause duration. The identification of these acoustic parameters has important clinical implications for the selection of PD management strategies. The association of F0 variability and pause duration with PD suggests that the neural circuits controlling these parameters are at least partly shared and might include the basal ganglia. While the current study focused on the phonetic realization of prosodic cues, future studies should examine whether and how PD affects prosody at higher levels of processing.

SUPPLEMENTAL MATERIAL

https://doi.org/10.23641/asha.25892923.

Machine Learning Models for Parkinson Disease: Systematic Review

Background

With the increasing availability of data, computing resources, and easier-to-use software libraries, machine learning (ML) is increasingly used in disease detection and prediction, including for Parkinson disease (PD). Despite the large number of studies published every year, very few ML systems have been adopted for real-world use. In particular, a lack of external validity may result in poor performance of these systems in clinical practice. Additional methodological issues in ML design and reporting can also hinder clinical adoption, even for applications that would benefit from such data-driven systems.

Objective

To sample the current ML practices in PD applications, we conducted a systematic review of studies published in 2020 and 2021 that used ML models to diagnose PD or track PD progression.

Methods

We conducted a systematic literature review in accordance with PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines in PubMed between January 2020 and April 2021, using the following exact string: "Parkinson's" AND ("ML" OR "prediction" OR "classification" OR "detection" or "artificial intelligence" OR "AI"). The search resulted in 1085 publications. After a search query and review, we found 113 publications that used ML for the classification or regression-based prediction of PD or PD-related symptoms.

Results

Only 65.5% (74/113) of studies used a holdout test set to avoid potentially inflated accuracies, and approximately half (25/46, 54%) of the studies without a holdout test set did not state this as a potential concern. Surprisingly, 38.9% (44/113) of studies did not report on how or if models were tuned, and an additional 27.4% (31/113) used ad hoc model tuning, which is generally frowned upon in ML model optimization. Only 15% (17/113) of studies performed direct comparisons of results with other models, severely limiting the interpretation of results.

Conclusions

This review highlights the notable limitations of current ML systems and techniques that may contribute to a gap between reported performance in research and the real-life applicability of ML models aiming to detect and predict diseases such as PD.

Global Acoustic Speech Temporal Characteristics for Mandarin Speakers With Parkinson's Disease During Syllable Repetition and Passage Reading

PURPOSE

Previous research has revealed considerable variation in speech rates among English speakers with Parkinson's disease (PD) with slower, faster, or similar rates than controls. The purpose of this study was to characterize speech rates of Mandarin speakers with PD and the corresponding articulation and pause characteristics explaining the speech rates to enhance rate control therapies.

METHOD

Eighteen Mandarin speakers with PD and 18 controls produced syllable repetitions and passage reading using their typical speech style. Speech rates, articulation rates, mean pause durations (≥ 10 ms), and the number of pauses with duration between 10 ms and 300 ms and greater than 300 ms were measured and compared between groups and tasks as well as across the initial, middle, and final periods of the passage. Two-way, mixed-model analyses of variance were employed for data analysis.

RESULTS

Compared to controls, individuals with PD spoke with similar speech rates and faster articulation rates during passage reading, whereas during syllable repetitions, they produced slower speech rates and comparable articulation rates. The slower syllable repetitions produced by speakers with PD may be explained by longer pauses and more perceptual pauses, whereas faster articulation rates may explain the trend of faster speech rates during reading. Speech and articulation rates accelerated for both groups during passage reading.

CONCLUSIONS

Speech rates of Mandarin speakers with PD were characterized by faster articulation, longer pauses, and more perceptual pauses for passage reading. A descriptive model of speech rate suggested that speakers with PD and dysarthria in this study would benefit from rate reduction therapy decreasing articulation rate.

SUPPLEMENTAL MATERIAL

https://doi.org/10.23641/asha.23982282.

Voice improvement following conventional speech therapy combined with singing intervention in people with Parkinson's disease: A three-arm randomised controlled trial

BACKGROUND

Although speech and voice disorders are common in Parkinson's disease (PD), there is insufficient evidence to support the effectiveness of behavioural speech therapies in these patients.

AIMS

This study aimed to examine the effects of a new tele-rehabilitation program, a combining of conventional speech therapy and singing intervention, on voice deficits in patients with PD.

METHODS & PROCEDURES

This study was a three-armed, assessor-masked, randomised controlled trial. Thirty-three people with PD were randomly assigned to the combination therapy, conventional speech therapy, or singing intervention group. This study followed the Consolidated Standards of Reporting Trials guidelines for non-pharmacological treatment. Each patient participated in 12 tele-rehabilitation sessions over 4 weeks. The combination therapy group received speech and singing interventions simultaneously (respiratory, speech, voice, and singing exercises). Voice intensity as a primary outcome and the voice handicap index (VHI), maximum frequency range, jitter and shimmer as secondary outcomes were evaluated 1 week before the first intervention session, 1 week after the last intervention session and 3 months after the last evaluation.

OUTCOMES & RESULTS

The results of repeated measures analysis of variance showed a significant main effect of time on all outcomes in all three groups after treatment (p < 0.001). There was a significant group effect for voice intensity (p < 0.001), VHI (p < 0.001), maximum frequency range (p = 0.014) and shimmer (p = 0.001). The combination therapy group demonstrated a significant outperformance in the VHI and shimmer than the speech therapy (p = 0.038) and singing intervention (p < 0.001) groups. The results of this study also indicated that combination therapy group compared to singing intervention group had a larger effect on voice intensity (p < 0.001), shimmer (p < 0.001) and maximum frequency range (p = 0.048).

CONCLUSIONS & IMPLICATION

The results demonstrated that combining speech therapy with a singing intervention delivered through tele-rehabilitation might be more effective in improving voice problems in patients with PD.

WHAT THIS PAPER ADDS

What is already known on the subject Parkinson's disease (PD) is a neurological disorder that frequently causes disturbances in speech and voice, which negatively affect patients' quality of life. Although speech difficulties occur in 90% of patients with PD, evidence-based treatment options for speech and language problems in these patients are limited. Therefore, further studies are required to develop and assess evidence-based treatment programs. What this study adds The findings of this study showed that a combination therapy program including conventional speech therapy approaches and individual singing intervention provided through tele-rehabilitation may have a greater effect on the improvement of voice problems in people with PD compared to speech therapy and singing intervention alone. What are the clinical implications of this work? Tele-rehabilitation combination therapy is an inexpensive and enjoyable behavioural treatment. The advantages of this method are that it is easy to access, appropriate for many stages of voice problems in PD, requires no prior singing training, encourages voice health and self-management and maximises treatment resources available to people with PD. We believe that the results of this study can provide a new clinical basis for treatment of voice disorders in people with PD.

Vowel production: a potential speech biomarker for early detection of dysarthria in Parkinson's disease

Objectives

Our aim is to detect early, subclinical speech biomarkers of dysarthria in Parkinson's disease (PD), i.e., systematic atypicalities in speech that remain subtle, are not easily detectible by the clinician, so that the patient is labeled "non-dysarthric." Based on promising exploratory work, we examine here whether vowel articulation, as assessed by three acoustic metrics, can be used as early indicator of speech difficulties associated with Parkinson's disease.

Study design

This is a prospective case-control study.

Methods

Sixty-three individuals with PD and 35 without PD (healthy controls-HC) participated in this study. Out of 63 PD patients, 43 had been diagnosed with dysarthria (DPD) and 20 had not (NDPD). Sustained vowels were recorded for each speaker and formant frequencies were measured. The analyses focus on three acoustic metrics: individual vowel triangle areas (tVSA), vowel articulation index (VAI) and the Phi index.

Results

tVSA were found to be significantly smaller for DPD speakers than for HC. The VAI showed significant differences between these two groups, indicating greater centralization and lower vowel contrasts in the DPD speakers with dysarhtria. In addition, DPD and NDPD speakers had lower Phi values, indicating a lower organization of their vowel system compared to the HC. Results also showed that the VAI index was the most efficient to distinguish between DPD and NDPD whereas the Phi index was the best acoustic metric to discriminate NDPD and HC.

Conclusion

This acoustic study identified potential subclinical vowel-related speech biomarkers of dysarthria in speakers with Parkinson's disease who have not been diagnosed with dysarthria.

Continuous theta burst stimulation over right cerebellum for speech impairment in Parkinson's disease: study protocol for a randomized, sham-controlled, clinical trial

Background

Speech impairment is a common symptom of Parkinson's disease (PD) that worsens with disease progression and affects communication and quality of life. Current pharmacological and surgical treatments for PD have inconsistent effects on speech impairment. The cerebellum is an essential part of sensorimotor network that regulates speech production and becomes dysfunctional in PD. Continuous theta-burst stimulation (cTBS) is a non-invasive brain stimulation technique that can modulate the cerebellum and its connections with other brain regions.

Objective

To investigate whether cTBS over the right cerebellum coupled with speech-language therapy (SLT) can improve speech impairment in PD.

Methods

In this randomized controlled trial (RCT), 40 patients with PD will be recruited and assigned to either an experimental group (EG) or a control group (CG). Both groups will receive 10 sessions of standard SLT. The EG will receive real cTBS over the right cerebellum, while the CG will receive sham stimulation. Blinded assessors will evaluate the treatment outcome at three time points: pre-intervention, post-intervention, and at a 12-week follow-up. The primary outcome measures are voice/speech quality and neurobehavioral parameters of auditory-vocal integration. The secondary outcome measures are cognitive function, quality of life, and functional connectivity determined by resting-state functional magnetic resonance imaging (fMRI).

Significance

This trial will provide evidence for the efficacy and safety of cerebellar cTBS for the treatment of speech impairment in PD and shed light on the neural mechanism of this intervention. It will also have implications for other speech impairment attributed to cerebellar dysfunctions.

Clinical trial registration

www.chictr.org.cn, identifier ChiCTR2100050543.

Monitoring the Effect of Levodopa Using Sustained Phonemes in Parkinson's Disease Patients

Parkinson's disease (PD) is a neurological disease identified by multiple symptoms, and levodopa is one of the most effective medications for treating the disease. To determine the dosage of levodopa, it is necessary to meet on a regular basis and observe motor function. The early detection and progression of the disease have been proposed using hypokinetic dysarthria. However, previous studies have not examined the effects of levodopa on speech rigorously and have provided inconsistent results. In this study, three sustained phonemes of PD patients were investigated for the effect of medication. A set of features characterizing vocal fold dynamics as well as the vocal tract coordinators were extracted from the sustained phonemes /of 28 PD patients during levodopa medication off and on states. All the features were statistically investigated and classified using a linear discriminant analysis (LDA) classifier. LDA classifier identified medication on from medication off based on the combined features from phoneme /a/, /o/ and /m/ with the accuracy=82.75% and F1-score=82.18%. Voice recording of PD patients during sustained phonemes /a/, /o/ and /m/ has the potential for identifying whether the patients are in On state or Off state of medication.Clinical Relevance- The outcomes of this study have the potential to monitor the effect and progress of levodopa on PD patients.

Short-term effect of dopaminergic medication on speech in early-stage Parkinson's disease

The effect of dopaminergic medication on speech has rarely been examined in early-stage Parkinson's disease (PD) and the respective literature is inconclusive and limited by inappropriate design with lack of PD control group. The study aims to examine the short-term effect of dopaminergic medication on speech in PD using patients with good motor responsiveness to levodopa challenge compared to a control group of PD patients with poor motor responsiveness. A total of 60 early-stage PD patients were investigated before (OFF) and after (ON) acute levodopa challenge and compared to 30 age-matched healthy controls. PD patients were categorised into two clinical subgroups (PD responders vs. PD nonresponders) according to the comparison of their motor performance based on movement disorder society-unified Parkinson's disease rating scale, part III. Seven distinctive parameters of hypokinetic dysarthria were examined using quantitative acoustic analysis. We observed increased monopitch (p > 0.01), aggravated monoloudness (p > 0.05) and longer duration of stop consonants (p > 0.05) in PD compared to healthy controls, confirming the presence of hypokinetic dysarthria in early PD. No speech alterations from OFF to ON state were revealed in any of the two PD groups and speech dimensions investigated including monopitch, monoloudness, imprecise consonants, harsh voice, slow sequential motion rates, articulation rate, or inappropriate silences, although a subgroup of PD responders manifested obvious improvement in motor function after levodopa intake (p > 0.001). Since the short-term usage of levodopa does not easily affect voice and speech performance in PD, speech assessment may provide a medication state-independent motor biomarker of PD.

Feedback and Feedforward Auditory-Motor Processes for Voice and Articulation in Parkinson's Disease

PURPOSE

Unexpected and sustained manipulations of auditory feedback during speech production result in "reflexive" and "adaptive" responses, which can shed light on feedback and feedforward auditory-motor control processes, respectively. Persons with Parkinson's disease (PwPD) have shown aberrant reflexive and adaptive responses, but responses appear to differ for control of vocal and articulatory features. However, these responses have not been examined for both voice and articulation in the same speakers and with respect to auditory acuity and functional speech outcomes (speech intelligibility and naturalness).

METHOD

Here, 28 PwPD on their typical dopaminergic medication schedule and 28 age-, sex-, and hearing-matched controls completed tasks yielding reflexive and adaptive responses as well as auditory acuity for both vocal and articulatory features.

RESULTS

No group differences were found for any measures of auditory-motor control, conflicting with prior findings in PwPD while off medication. Auditory-motor measures were also compared with listener ratings of speech function: first formant frequency acuity was related to speech intelligibility, whereas adaptive responses to vocal fundamental frequency manipulations were related to speech naturalness.

CONCLUSIONS

These results support that auditory-motor processes for both voice and articulatory features are intact for PwPD receiving medication. This work is also the first to suggest associations between measures of auditory-motor control and speech intelligibility and naturalness.

The Relationship Between Voice Onset Time and Increase in Vocal Effort and Fundamental Frequency

Purpose Prior work suggests that voice onset time (VOT) may be impacted by laryngeal tension: VOT means decrease when individuals with typical voices increase their fundamental frequency (f o) and VOT variability is increased in individuals with vocal hyperfunction, a voice disorder characterized by increased laryngeal tension. This study further explored the relationship between VOT and laryngeal tension during increased f o, vocal effort, and vocal strain. Method Sixteen typical speakers of American English were instructed to produce VOT utterances under four conditions: baseline, high pitch, effort, and strain. Repeated-measures analysis of variance models were used to analyze the effects of condition on VOT means and standard deviations (SDs); pairwise comparisons were used to determine significant differences between conditions. Results Voicing, condition, and their interaction significantly affected VOT means. Voiceless VOT means significantly decreased for high pitch (p < .001) relative to baseline; however, no changes in voiceless VOT means were found for effort or strain relative to baseline. Although condition had a significant effect on VOT SDs, there were no significant differences between effort, strain, and high pitch conditions relative to baseline. Conclusions Speakers with typical voices likely engage different musculature to increase pitch than to increase vocal effort and strain. The increased VOT variability present with vocal hyperfunction is not seen in individuals with typical voices using increased effort and strain, supporting the assertion that this feature of vocal hyperfunction may be related to disordered vocal motor control rather than resulting from effortful voice production.

Detecting Effect of Levodopa in Parkinson's Disease Patients Using Sustained Phonemes

BACKGROUND

Parkinson's disease (PD) is a multi-symptom neurodegenerative disease generally managed with medications, of which levodopa is the most effective. Determining the dosage of levodopa requires regular meetings where motor function can be observed. Speech impairment is an early symptom in PD and has been proposed for early detection and monitoring of the disease. However, findings from previous research on the effect of levodopa on speech have not shown a consistent picture.

METHOD

This study has investigated the effect of medication on PD patients for three sustained phonemes; /a/, /o/, and /m/, which were recorded from 24 PD patients during medication off and on stages, and from 22 healthy participants. The differences were statistically investigated, and the features were classified using Support Vector Machine (SVM).

RESULTS

The results show that medication has a significant effect on the change of time and amplitude perturbation (jitter and shimmer) and harmonics of /m/, which was the most sensitive individual phoneme to the levodopa response. /m/ and /o/ performed at a comparable level in discriminating PD-off from control recordings. However, SVM classifications based on the combined use of the three phonemes /a/, /o/, and /m/ showed the best classifications, both for medication effect and for separating PD from control voice. The SVM classification for PD-off versus PD-on achieved an AUC of 0.81.

CONCLUSION

Studies of phonation by computerized voice analysis in PD should employ recordings of multiple phonemes. Our findings are potentially relevant in research to identify early parkinsonian dysarthria, and to tele-monitoring of the levodopa response in patients with established PD.

Worldwide Healthy Adult Voice Baseline Parameters: A Comprehensive Review

The voice results in acoustic signals analyzed and synthetized at first for telecommunication matters, and more recently investigated for medical purposes. In particular, voice signal characteristics can evidence individual health conditions useful for screening, diagnostic and remote monitoring aims. Within this frame, the knowledge of baseline features of healthy voice is mandatory, in order to balance a comparison with their unhealthy counterpart. However, the baseline features of the human voice depend on gender, age-range and ethnicity and, as far as we know, no work reports as those features spread worldwide. This paper intends to cover this lack. Our database research yielded 179 relevant published studies, retrieved using digital libraries of IEEE Xplore, Scopus, Web of Science, Iop Science, Taylor and Francis Online, and Scitepress. These relevant studies report different features, among which here we consider the most investigated ones, within the most investigated age-range. In particular, the features are the fundamental frequency, the jitter, the shimmer, the harmonic-to-noise ratio, and the cepstral peak prominence, the most investigated age-range is within 20-40 years and, related to the ethnicity, 20 countries are considered.

The physical significance of acoustic parameters and its clinical significance of dysarthria in Parkinson's disease

Dysarthria is universal in Parkinson’s disease (PD) during disease progression; however, the quality of vocalization changes is often ignored. Furthermore, the role of changes in the acoustic parameters of phonation in PD patients remains unclear. We recruited 35 PD patients and 26 healthy controls to perform single, double, and multiple syllable tests. A logistic regression was performed to differentiate between protective and risk factors among the acoustic parameters. The results indicated that the mean f0, max f0, min f0, jitter, duration of speech and median intensity of speaking for the PD patients were significantly different from those of the healthy controls. These results reveal some promising indicators of dysarthric symptoms consisting of acoustic parameters, and they strengthen our understanding about the significance of changes in phonation by PD patients, which may accelerate the discovery of novel PD biomarkers.

Orofacial Strength and Voice Quality as Outcome of Levodopa Challenge Test in Parkinson Disease

OBJECTIVE

To assess the usefulness of orofacial strength and voice quality as assessment of response to levodopa challenge test (LCT) used in the diagnosis of early idiopathic Parkinson disease (IPD).

STUDY DESIGN

Controlled Prospective Study.

METHODS

From January 2014 to April 2019, patients with early IPD and healthy individuals were recruited and evaluated for clinical findings (Hoehn and Yahr scale; Unified Parkinson's Disease Rating Scale); Voice Handicap Index (VHI); grade of dysphonia, roughness, breathiness, asthenia, and strain and instability (GRBASI); maximal phonation time; phonation quotient; acoustic parameters; and orofacial muscle strength Oral Performance Instrument (IOPI; IOPI Medical, Woodinville, WA, USA) t) at baseline and 45 minutes after the levodopa intake (LCT).

RESULTS

A total of 32 IPD patients and 20 healthy individuals completed the study. Healthy individuals exhibited better VHI, grade of dysphonia, breathiness, asthenia, strain, instability, and acoustic measurements (noise-related, tremor, F0 short- and mid-term and intensity short-term parameters) than healthy subjects. The mean values of muscle strength of lips, cheeks, fundamental frequency (F0), highest F0, and shimmer significantly improved from pre- to post-LCT in IPD patients. Healthy individuals did not exhibit significant changes of orofacial strength and voice quality assessment from pre- to post-LCT. Significant associations were found between clinical, orofacial strength, and some aerodynamic and acoustic measurements.

CONCLUSION

Orofacial strength and acoustic voice quality measurements may be used as objective outcomes of the LCT responsiveness in patients with early IPD.

LEVEL OF EVIDENCE

3A. Laryngoscope, 2020.

Effects of utterance rate and length on the spatiotemporal index in Parkinson's disease

Purpose: To characterise labial articulatory pattern variability using the spatiotemporal index (STI) in speakers with idiopathic Parkinson's disease (PD) across different speaking rates and syllable-sentence conditions compared to age- and sex-matched healthy controls.Method: Ten speakers with mild-severe idiopathic PD and 10 controls produced "pa" and the Rainbow Passage at slow, typical and fast speech rates. Upper lip and lower lip kinematics were digitised during a motion capture system. Data were analysed using linear mixed modelling.Result: Regardless of the participant group, a high STI value was observed in the fast speech rate for the "pa" syllable condition, particularly for movements of the lower lip. As utterance rate increased, the control group showed the highest variability, followed by PD OFF and PD ON conditions. Syllable "pa" showed a greater STI value compared to both the first and second utterance of Rainbow Passage.Conclusion: PD manifests sufficient residual capacity to achieve near-normal motor compensation to preserve the consistency of lower lip movements during speech production. The lack of a significant difference in lip STI values between ON-OFF medication states suggests that dopaminergic treatment does not influence stability of speech for individuals with mild-moderate stage PD.

Voice changes in Parkinson's disease: What are they telling us?

Emerging evidence suggests voice dysfunction is the earliest sign of motor impairment in Parkinson's disease (PD). The complexity and fine motor control involved in vocalization may result in dysfunction here before the limbs. The voice in PD demonstrates characteristic changes on perceptual and acoustic analyses. The physiological and anatomical correlates of these have been investigated through laryngoscopy, stroboscopy, photoglottography, laryngeal electromyography, computed-tomography, pulmonary function testing and aerodynamic assessments. These have revealed numerous abnormalities including incomplete glottic closure and vocal fold hypoadduction/bowing to account for these voice changes. Many of these phenomena are likely related to rigidity or bradykinesia of the laryngeal muscles. The early onset of voice changes is resonant with the pathophysiological insights offered by Braak's hypothesis and murine models of the disease. These physiological abnormalities and pathological models largely stand to support dopaminergic and non-dopaminergic mechanisms being implicated in the pathogenesis of voice dysfunction. This review focuses on characterizing the voice changes in PD. These stand as a promising area of enquiry to further our understanding of the pathophysiology of the disease and offer potential to be utilized as an early diagnostic biomarker or marker of disease progression.

Research-based Updates in Swallowing and Communication Dysfunction in Parkinson Disease: Implications for Evaluation and Management

PURPOSE

Individuals with Parkinson disease (PD) present with complex and variable symptoms, with recent findings suggesting that the etiology of PD extends beyond the involvement of just the basal ganglia. These symptoms include significant impairments in the speech and swallowing domains, which can greatly affect quality of life and therefore require therapeutic attention. This research-based update reviews the neurophysiological basis for swallowing and speech changes in PD, the effectiveness of various types of treatments, and implications for symptom evaluation and management.

CONCLUSION

The mechanisms responsible for swallowing and speech symptoms in PD remain largely unknown. Dopaminergic medication and deep-brain-stimulation do not provide consistent benefits for these symptoms suggesting a non-dopaminergic network is involved. Importantly, evidence suggests that symptoms of dysphagia and hypokinetic dysarthria may be early indications of PD, so it is critical to investigate the cause of these changes.

Spectral/Cepstral Analyses of Phonation in Parkinson's Disease before and after Voice Treatment: A Preliminary Study

PURPOSE

This article examines cepstral/spectral analyses of sustained /α/ vowels produced by speakers with hypokinetic dysarthria secondary to idiopathic Parkinson's disease (PD) before and after Lee Silverman Voice Treatment (LSVT®LOUD) and the relationship of these measures with overall voice intensity.

METHODOLOGY

Nine speakers with PD were examined in a pre-/post-treatment design, with multiple daily audio recordings before and after treatment. Sustained vowels were analyzed for cepstral peak prominence (CPP), CPP standard deviation (CPP SD), low/high spectral ratio (L/H SR), and Cepstral/Spectral Index of Dysphonia (CSID) using the KAYPENTAX computer software.

RESULTS

CPP and CPP SD increased significantly and CSID decreased significantly from pre- to post-treatment recordings, with strong effect sizes. Increased CPP indicates increased dominance of harmonics in the spectrum following LSVT. After restricting the frequency cutoff to the region just above the first formant and second formant and below the third formant, L/H SR was observed to decrease significantly following treatment. Correlation analyses demonstrated that CPP was more strongly associated with CSID before treatment than after.

CONCLUSION

In addition to increased vocal intensity following LSVT, speakers with PD exhibited both improved harmonic structure and voice quality as reflected by cepstral/spectral analysis, indicating that there was improved harmonic structure and reduced dysphonia following treatment.

Voice quality severity and responsiveness to levodopa in Parkinson's disease

The effect of levodopa on perceptual and acoustic measures of voice quality was examined in fifty-one individuals with Parkinson's disease (IWPD). IWPDs produced prolonged vowels while on and off levodopa. Acoustic measures included jitter, shimmer, harmonic-to-noise ratio, cepstral peak prominence and the Acoustic Voice Quality Index. A perceptual measure of overall voice quality was obtained from 3 listeners. When the IWPDs were examined as a group, no significant difference was found between on and off levodopa conditions. In contrast, when IWPDs were split into two groups based on voice quality severity, a significant group-by-medication state interaction emerged. In addition, there was a significant correlation (r = .55) between the magnitude of levodopa-related improvement in perceived voice quality and voice quality severity. In contrast, levodopa-related improvement in voice quality was not correlated with duration of disease or levodopa use. Results do not support the hypothesis of reduced levodopa-responsiveness to voice symptoms as disease duration increases. Instead, the results suggest that the magnitude of the levodopa response may increase with increasing severity of the voice quality symptoms. These results suggest that the severity of speech and voice symptoms needs to be given greater consideration in future studies of levodopa effectiveness in IWPDs.

Impact of levodopa treatment in the voice pattern of Parkinson’s disease patients: a systematic review and meta-analysis

Abstract Purpose Investigate the association between levodopa therapy and vocal characteristics in Parkinson’s disease patients. Search strategy Studies published at MEDLINE, LILACS, and SciELO, from 1960 to December 2016. A systematic review and meta-analysis was performed using the following keywords: Parkinson’s disease; levodopa; L-dopa; voice; speech disorders; dysphonia; dysarthria. After analyzing titles and abstracts, two independent reviewers selected all clinical trials that met the eligibility criteria and selected the articles and the data recorded in a previously standardized table. Selection criteria Trials published in English between 1960 and December 2016 individuals with clinical diagnosis of Parkinson’s disease; use of levodopa therapy in stable doses; acoustic analysis combined or not with auditory-perceptual analysis to evaluate the vocal parameters under investigation. Data analysis The following vocal parameters were analyzed: fundamental frequency (F 0), jitter, and vocal intensity. Standardized mean differences (SMD) were calculated using the Comprehensive Meta-analysis V2 software. Results Nine articles met the eligibility criteria and were selected, with a total of 119 individuals. From these, six articles with 83 individuals were included in the meta-analysis. During the levodopa therapy “on” state, modifications in F 0 (SMD=0.39; 95% CI - 0.21-0.57) and jitter (SMD=0.23; 95% CI - 0.02-0.45) were observed. Vocal intensity was not affected (SMD=0.09; 95% CI - 0.22-0.39) by levodopa ingestion. Data of the included studies were controversial in the auditory-perceptual analysis of voice. Conclusion Levodopa therapy modifies F0 and jitter. No changes in vocal intensity were observed in either the “on” or “off” states of levodopa therapy.

Quantitative Analysis of Relationship Between Hypokinetic Dysarthria and the Freezing of Gait in Parkinson's Disease

Hypokinetic dysarthria (HD) and freezing of gait (FOG) are both axial symptoms that occur in patients with Parkinson's disease (PD). It is assumed they have some common pathophysiological mechanisms and therefore that speech disorders in PD can predict FOG deficits within the horizon of some years. The aim of this study is to employ a complex quantitative analysis of the phonation, articulation and prosody in PD patients in order to identify the relationship between HD and FOG, and establish a mathematical model that would predict FOG deficits using acoustic analysis at baseline. We enrolled 75 PD patients who were assessed by 6 clinical scales including the Freezing of Gait Questionnaire (FOG-Q). We subsequently extracted 19 acoustic measures quantifying speech disorders in the fields of phonation, articulation and prosody. To identify the relationship between HD and FOG, we performed a partial correlation analysis. Finally, based on the selected acoustic measures, we trained regression models to predict the change in FOG during a 2-year follow-up. We identified significant correlations between FOG-Q scores and the acoustic measures based on formant frequencies (quantifying the movement of the tongue and jaw) and speech rate. Using the regression models, we were able to predict a change in particular FOG-Q scores with an error of between 7.4 and 17.0 %. This study is suggesting that FOG in patients with PD is mainly linked to improper articulation, a disturbed speech rate and to intelligibility. We have also proved that the acoustic analysis of HD at the baseline can be used as a predictor of the FOG deficit during 2 years of follow-up. This knowledge enables researchers to introduce new cognitive systems that predict gait difficulties in PD patients.

Voice Quality and Orofacial Strength as Outcome of Levodopa Effectiveness in Patients with Early Idiopathic Parkinson Disease: A Preliminary Report

INTRODUCTION

Sixty to 90% of patients with idiopathic Parkinson disease (IPD) developed early dysphonia and subtle speech impairment, which is usually related to orofacial muscular dysfunctions. The aim of this preliminary study is to assess the usefulness of voice quality and orofacial strength (involved in speech) as outcome of levodopa challenge test used for the IPD diagnosis.

MATERIAL AND METHODS

A total of 20 patients with early IPD were recruited and evaluated for clinical findings (Hoehn and Yahr scale), voice handicap index, maximal phonation time, phonation quotient, percent jitter, percent shimmer, noise-to-harmonic ratio, and orofacial muscular strength (Iowa Oral Performance Instrument) at baseline, throughout the levodopa challenge test and after therapeutic stabilization.

RESULTS

The intake of a standardized dose of levodopa (levodopa challenge test) significantly improved phonation quotient and percent shimmer. We did not find similar improvement after medical stabilization of patients (based on levodopa medication) despite an improvement of Hoehn and Yahr mean score. The intake of levodopa significantly improved cheeks and lips strength involved in speech quality both along the challenge test and after the therapeutic stabilization.

CONCLUSIONS

These preliminary findings support a differential impact of levodopa on voice and speech functions in early diagnosed IPD and a mismatch between the clinical examination, orofacial strength, and voice quality improvements once the patient is medically stabilized.

Sensorimotor adaptation of voice fundamental frequency in Parkinson's disease

OBJECTIVE

This study examined adaptive responses to auditory perturbation of fundamental frequency (fo) in speakers with Parkinson's disease (PD) and control speakers.

METHOD

Sixteen speakers with PD and nineteen control speakers produced sustained vowels while they received perturbed auditory feedback (i.e., fo shifted upward or downward). Speakers' pitch acuity was quantified using a just-noticeable-difference (JND) paradigm. Twelve listeners provided estimates of the speech intelligibility for speakers with PD.

RESULTS

Fifteen responses from each speaker group for each shift direction were included in analyses. While control speakers generally showed consistent adaptive responses opposing the perturbation, speakers with PD showed no compensation on average, with individual PD speakers showing highly variable responses. In the PD group, the degree of compensation was not significantly correlated with age, disease progression, pitch acuity, or intelligibility.

CONCLUSIONS

These findings indicate reduced adaptation to sustained fo perturbation and higher variability in PD compared to control participants. No significant differences were seen in pitch acuity between groups, suggesting that the fo adaptation deficit in PD is not the result of purely perceptual mechanisms.

SIGNIFICANCE

These results suggest there is an impairment in vocal motor control in PD. Building on these results, contributions can be made to developing targeted voice treatments for PD.

Speech and Voice Response to a Levodopa Challenge in Late-Stage Parkinson's Disease

BACKGROUND

Parkinson's disease (PD) patients are affected by hypokinetic dysarthria, characterized by hypophonia and dysprosody, which worsens with disease progression. Levodopa's (l-dopa) effect on quality of speech is inconclusive; no data are currently available for late-stage PD (LSPD).

OBJECTIVE

To assess the modifications of speech and voice in LSPD following an acute l-dopa challenge.

METHOD

LSPD patients [Schwab and England score <50/Hoehn and Yahr stage >3 (MED ON)] performed several vocal tasks before and after an acute l-dopa challenge. The following was assessed: respiratory support for speech, voice quality, stability and variability, speech rate, and motor performance (MDS-UPDRS-III). All voice samples were recorded and analyzed by a speech and language therapist blinded to patients' therapeutic condition using Praat 5.1 software.

RESULTS

24/27 (14 men) LSPD patients succeeded in performing voice tasks. Median age and disease duration of patients were 79 [IQR: 71.5-81.7] and 14.5 [IQR: 11-15.7] years, respectively. In MED OFF, respiratory breath support and pitch break time of LSPD patients were worse than the normative values of non-parkinsonian. A correlation was found between disease duration and voice quality (R = 0.51; p = 0.013) and speech rate (R = -0.55; p = 0.008). l-Dopa significantly improved MDS-UPDRS-III score (20%), with no effect on speech as assessed by clinical rating scales and automated analysis.

CONCLUSION

Speech is severely affected in LSPD. Although l-dopa had some effect on motor performance, including axial signs, speech and voice did not improve. The applicability and efficacy of non-pharmacological treatment for speech impairment should be considered for speech disorder management in PD.

Dysphonic Voice Pattern Analysis of Patients in Parkinson's Disease Using Minimum Interclass Probability Risk Feature Selection and Bagging Ensemble Learning Methods

Analysis of quantified voice patterns is useful in the detection and assessment of dysphonia and related phonation disorders. In this paper, we first study the linear correlations between 22 voice parameters of fundamental frequency variability, amplitude variations, and nonlinear measures. The highly correlated vocal parameters are combined by using the linear discriminant analysis method. Based on the probability density functions estimated by the Parzen-window technique, we propose an interclass probability risk (ICPR) method to select the vocal parameters with small ICPR values as dominant features and compare with the modified Kullback-Leibler divergence (MKLD) feature selection approach. The experimental results show that the generalized logistic regression analysis (GLRA), support vector machine (SVM), and Bagging ensemble algorithm input with the ICPR features can provide better classification results than the same classifiers with the MKLD selected features. The SVM is much better at distinguishing normal vocal patterns with a specificity of 0.8542. Among the three classification methods, the Bagging ensemble algorithm with ICPR features can identify 90.77% vocal patterns, with the highest sensitivity of 0.9796 and largest area value of 0.9558 under the receiver operating characteristic curve. The classification results demonstrate the effectiveness of our feature selection and pattern analysis methods for dysphonic voice detection and measurement.

The diagnosis, clinical findings and treatment options for Parkinson's disease patients attending a tertiary referral voice clinic

BACKGROUND

Parkinson's disease is a degenerative disorder of the central nervous system, mainly affecting motor functions including the voice. The aetiology of dysphonia changes throughout the course of disease progression.

OBJECTIVES

This study aimed to determine the laryngeal changes seen in early-, mid- and late-stage Parkinson's disease. Thirteen patients with Parkinson's disease are presented, representing the largest series of voice patients with Parkinson's disease seen in a voice clinic in the literature.

METHOD

Age, gender, severity of handicap caused by voice disorder and possible associated reflux symptoms were examined.

RESULTS

Laryngeal function appeared to change gradually with progression of the disease, and may have been affected by the presence of pre-existing laryngeal pathology.

CONCLUSION

Laryngeal function in Parkinson's disease appears to go through a series of changes that may be helped by both therapeutic and surgical interventions. These patients should be treated within the confines of a voice clinic multidisciplinary model.

Dysarthria in individuals with Parkinson's disease: a protocol for a binational, cross-sectional, case-controlled study in French and European Portuguese (FraLusoPark)

INTRODUCTION

Individuals with Parkinson's disease (PD) have to deal with several aspects of voice and speech decline and thus alteration of communication ability during the course of the disease. Among these communication impairments, 3 major challenges include: (1) dysarthria, consisting of orofacial motor dysfunction and dysprosody, which is linked to the neurodegenerative processes; (2) effects of the pharmacological treatment, which vary according to the disease stage; and (3) particular speech modifications that may be language-specific, that is, dependent on the language spoken by the patients. The main objective of the FraLusoPark project is to provide a thorough evaluation of changes in PD speech as a result of pharmacological treatment and disease duration in 2 different languages (French vs European Portuguese).

METHODS AND ANALYSIS

Individuals with PD are enrolled in the study in France (N=60) and Portugal (N=60). Their global motor disability and orofacial motor functions is assessed with specific clinical rating scales, without (OFF) and with (ON) pharmacological treatment. 2 groups of 60 healthy age-matched volunteers provide the reference for between-group comparisons. Along with the clinical examinations, several speech tasks are recorded to obtain acoustic and perceptual measures. Patient-reported outcome measures are used to assess the psychosocial impact of dysarthria on quality of life.

ETHICS AND DISSEMINATION

The study has been approved by the local responsible committees on human experimentation and is conducted in accordance with the ethical standards. A valuable large-scale database of speech recordings and metadata from patients with PD in France and Portugal will be constructed. Results will be disseminated in several articles in peer-reviewed journals and in conference presentations. Recommendations on how to assess speech and voice disorders in individuals with PD to monitor the progression and management of symptoms will be provided.

TRIAL REGISTRATION NUMBER

NCT02753192, Pre-results.

Clear Speech Variants: An Acoustic Study in Parkinson's Disease

PURPOSE

The authors investigated how different variants of clear speech affect segmental and suprasegmental acoustic measures of speech in speakers with Parkinson's disease and a healthy control group.

METHOD

A total of 14 participants with Parkinson's disease and 14 control participants served as speakers. Each speaker produced 18 different sentences selected from the Sentence Intelligibility Test (Yorkston & Beukelman, 1996). All speakers produced stimuli in 4 speaking conditions (habitual, clear, overenunciate, and hearing impaired). Segmental acoustic measures included vowel space area and first moment (M1) coefficient difference measures for consonant pairs. Second formant slope of diphthongs and measures of vowel and fricative durations were also obtained. Suprasegmental measures included fundamental frequency, sound pressure level, and articulation rate.

RESULTS

For the majority of adjustments, all variants of clear speech instruction differed from the habitual condition. The overenunciate condition elicited the greatest magnitude of change for segmental measures (vowel space area, vowel durations) and the slowest articulation rates. The hearing impaired condition elicited the greatest fricative durations and suprasegmental adjustments (fundamental frequency, sound pressure level).

CONCLUSIONS

Findings have implications for a model of speech production for healthy speakers as well as for speakers with dysarthria. Findings also suggest that particular clear speech instructions may target distinct speech subsystems.

Articulatory Changes in Vowel Production following STN DBS and Levodopa Intake in Parkinson's Disease

Purpose. To investigate the impact of deep brain stimulation of the subthalamic nucleus (STN DBS) and levodopa intake on vowel articulation in dysarthric speakers with Parkinson's disease (PD). Methods. Vowel articulation was assessed in seven Quebec French speakers diagnosed with idiopathic PD who underwent STN DBS. Assessments were conducted on- and off-medication, first prior to surgery and then 1 year later. All recordings were made on-stimulation. Vowel articulation was measured using acoustic vowel space and formant centralization ratio. Results. Compared to the period before surgery, vowel articulation was reduced after surgery when patients were off-medication, while it was better on-medication. The impact of levodopa intake on vowel articulation changed with STN DBS: before surgery, levodopa impaired articulation, while it no longer had a negative effect after surgery. Conclusions. These results indicate that while STN DBS could lead to a direct deterioration in articulation, it may indirectly improve it by reducing the levodopa dose required to manage motor symptoms. These findings suggest that, with respect to speech production, STN DBS and levodopa intake cannot be investigated separately because the two are intrinsically linked. Along with motor symptoms, speech production should be considered when optimizing therapeutic management of patients with PD.

Listener Perception of Monopitch, Naturalness, and Intelligibility for Speakers With Parkinson's Disease

PURPOSE

Given the potential significance of speech naturalness to functional and social rehabilitation outcomes, the objective of this study was to examine the effect of listener perceptions of monopitch on speech naturalness and intelligibility in individuals with Parkinson's disease (PD).

METHOD

Two short utterances were extracted from monologue samples of 16 speakers with PD and 5 age-matched adults without PD. Sixteen listeners evaluated these stimuli for monopitch, speech naturalness and intelligibility using the visual sort and rate method.

RESULTS

Naïve listeners can reliably judge monopitch, speech naturalness, and intelligibility with minimal familiarization. While monopitch and speech intelligibility were only moderately correlated, monopitch and speech naturalness were highly correlated.

CONCLUSIONS

A great deal of attention is currently being paid to improvement of vocal loudness and thus speech intelligibility in PD. Our findings suggest that prosodic characteristics such as monopitch should be explored as adjuncts to this treatment of dysarthria in PD. Development of such prosodic treatments may enhance speech naturalness and thus improve quality of life.

Effective dysphonia detection using feature dimension reduction and kernel density estimation for patients with Parkinson's disease

Detection of dysphonia is useful for monitoring the progression of phonatory impairment for patients with Parkinson's disease (PD), and also helps assess the disease severity. This paper describes the statistical pattern analysis methods to study different vocal measurements of sustained phonations. The feature dimension reduction procedure was implemented by using the sequential forward selection (SFS) and kernel principal component analysis (KPCA) methods. Four selected vocal measures were projected by the KPCA onto the bivariate feature space, in which the class-conditional feature densities can be approximated with the nonparametric kernel density estimation technique. In the vocal pattern classification experiments, Fisher's linear discriminant analysis (FLDA) was applied to perform the linear classification of voice records for healthy control subjects and PD patients, and the maximum a posteriori (MAP) decision rule and support vector machine (SVM) with radial basis function kernels were employed for the nonlinear classification tasks. Based on the KPCA-mapped feature densities, the MAP classifier successfully distinguished 91.8% voice records, with a sensitivity rate of 0.986, a specificity rate of 0.708, and an area value of 0.94 under the receiver operating characteristic (ROC) curve. The diagnostic performance provided by the MAP classifier was superior to those of the FLDA and SVM classifiers. In addition, the classification results indicated that gender is insensitive to dysphonia detection, and the sustained phonations of PD patients with minimal functional disability are more difficult to be correctly identified.

Progression of voice and speech impairment in the course of Parkinson's disease: a longitudinal study

Impairment of voice and speech occurs in the majority of patients in the course of Parkinson's disease (PD). The aim of the current study was to survey the changes of voice and speech performance in the individual patients over time. 80 patients with PD and 60 healthy speakers were tested and retested after at least 12 months (average time interval: 32.5 months). Participants had to read a given text which was digitally recorded as a source for the perceptual and acoustic analysis. Stage of the disease and global motor impairment were rated according to the accepted scales. As a result, abnormalities of voice and speech were already present in mildly affected patients and there were significant deteriorations of quality of voice and articulatory velocity and precision between baseline and followup examination which showed no correlation with the time interval between the visits. Summarized, voice, and speech performance were found to further deteriorate in the individual patient in the course of time although global motor impairment was widely stable which might be a hint for nondopaminergic mechanisms of progression of dysarthrophonia. Further investigations are warranted to get a better insight into the dynamics of the progression of voice and speech impairment in PD as a precondition for the development of therapeutic approaches.

Prosody and levodopa in Parkinsons disease

Objective Research is scarce regarding the use of prosodic parameters in the expression of attitudes in Parkinson’s disease (PD). The purpose of this study was to evaluate the parameters used in prosodic expression of attitudes in individuals with idiopathic PD and the effect of levodopa on these parameters. Method We studied the use of levodopa in 10 individuals with idiopathic PD during the “off” and “on” periods, and 10 individuals without neurological abnormalities. Results PD patients showed lower frequency measurements and longer duration measurements. The levodopa caused reduction in the duration parameter. Conclusion PD patients use prosody to express their attitudes in the same way as controls in both off and on periods. However, when attitudes are not taken into account, levodopa is effective in improving the duration parameter.

Relative fundamental frequency during vocal onset and offset in older speakers with and without Parkinson's disease

The relative fundamental frequency (RFF) surrounding production of a voiceless consonant has previously been shown to be lower in speakers with hypokinetic dysarthria and Parkinson's disease (PD) relative to age/sex matched controls. Here RFF was calculated in 32 speakers with PD without overt hypokinetic dysarthria and 32 age and sex matched controls to better understand the relationships between RFF and PD progression, medication status, and sex. Results showed that RFF was statistically significantly lower in individuals with PD compared with healthy age-matched controls and was statistically significantly lower in individuals diagnosed at least 5 yrs prior to experimentation relative to individuals recorded less than 5 yrs past diagnosis. Contrary to previous trends, no effect of medication was found. However, a statistically significant effect of sex on offset RFF was shown, with lower values in males relative to females. Future work examining the physiological bases of RFF is warranted.

Pitch variability in patients with Parkinson's disease: effects of deep brain stimulation of caudal zona incerta and subthalamic nucleus

PURPOSE

The purpose of the present study was to examine the effect of deep brain stimulation (DBS) of the subthalamic nucleus (STN) and the caudal zona incerta (cZi) pitch characteristics of connected speech in patients with Parkinson's disease (PD).

METHOD

The authors evaluated 16 patients preoperatively and 12 months after DBS surgery. Eight patients were implanted in the STN (ages 51-72 years; M = 63 years). Six received bilateral implantation and 2 unilateral (left) implantation. Eight patients were bilaterally implanted in the cZi (ages 49-71 years; M = 60.8 years). Preoperative assessments were made after a levodopa challenge (approximately 1.5 times the ordinary dose). All postoperative examinations were made off and on stimulation with a clinically optimized dose of levodopa. Measurements of pitch range and variability were obtained from each utterance in a recorded read speech passage.

RESULTS

Pitch range and coefficient of variation showed an increase in patients under STN-DBS. Patients under cZi-DBS showed no significant effects of treatment on investigated pitch properties.

CONCLUSION

STN-DBS was shown to increase pitch variation and range. The results provided no evidence of cZi-DBS having a beneficial effect on PD patients' pitch variability.

Evaluation of speech impairment in early stages of Parkinson's disease: a prospective study with the role of pharmacotherapy

Despite the initial reports showing beneficial effects of dopaminergic treatment on speech in Parkinson's disease (PD), more recent studies based upon valid measurements have not approved any improvement of speech performance under pharmacotherapy. The aim of this study was to analyze the effect of treatment initiation on the progression of speech impairment in PD, using novel evaluation criteria. Nineteen de novo patients with PD were tested and retested within 2 years after the introduction of antiparkinsonian therapy. As controls, 19 age-matched individuals were recorded. Speech examination included sustained phonation, fast syllable repetition, reading text, and monolog. Quantitative acoustic analyses of the key aspects of speech based on Gaussian kernel distribution, statistical decision-making theory, and healthy speech observation were used to assess the improvement or deterioration of speech. A trend for speech performances to improve was demonstrated after treatment mainly in quality of voice, intensity variability, pitch variability, and articulation. The treatment-related improvement differed in various aspects of speech for individual PD patients. Improvements in vowel articulation and pitch variability correlated with treatment-related changes in bradykinesia and rigidity, whereas voice quality and loudness variability improved independently. Using a novel approach of acoustic analysis and advanced statistics, improvements in speech performance can be demonstrated in PD patients after the introduction of antiparkinsonian therapy. Moreover, changes in speech articulation and pitch variability appear to be related with dopaminergic responsiveness of bradykinesia and rigidity. Therefore, speech may be a valuable marker of disease progression and treatment efficacy in PD.

Measures to Evaluate the Effects of DBS on Speech Production

The purpose of this paper is to review and evaluate measures of speech production that could be used to document effects of Deep Brain Stimulation (DBS) on speech performance, especially in persons with Parkinson disease (PD). A small set of evaluative criteria for these measures is presented first, followed by consideration of several speech physiology and speech acoustic measures that have been studied frequently and reported on in the literature on normal speech production, and speech production affected by neuromotor disorders (dysarthria). Each measure is reviewed and evaluated against the evaluative criteria. Embedded within this review and evaluation is a presentation of new data relating speech motions to speech intelligibility measures in speakers with PD, amyotrophic lateral sclerosis (ALS), and control speakers (CS). These data are used to support the conclusion that at the present time the slope of second formant transitions (F2 slope), an acoustic measure, is well suited to make inferences to speech motion and to predict speech intelligibility. The use of other measures should not be ruled out, however, and we encourage further development of evaluative criteria for speech measures designed to probe the effects of DBS or any treatment with potential effects on speech production and communication skills.

Impairment of vowel articulation as a possible marker of disease progression in Parkinson's disease

PURPOSE

The aim of the current study was to survey if vowel articulation in speakers with Parkinson's disease (PD) shows specific changes in the course of the disease.

METHOD

67 patients with PD (42 male) and 40 healthy speakers (20 male) were tested and retested after an average time interval of 34 months. Participants had to read a given text as source for subsequent calculation of the triangular vowel space area (tVSA) and vowel articulation index (VAI). Measurement of tVSA and VAI were based upon analysis of the first and second formant of the vowels /α/, /i/and /u/ extracted from defined words within the text.

RESULTS

At first visit, VAI values were reduced in male and female PD patients as compared to the control group, and showed a further decrease at the second visit. Only in female Parkinsonian speakers, VAI was correlated to overall speech impairment based upon perceptual impression. VAI and tVSA were correlated to gait impairment, but no correlations were seen between VAI and global motor impairment or overall disease duration. tVSA showed a similar reduction in the PD as compared to the control group and was also found to further decline between first and second examination in female, but not in male speakers with PD.

CONCLUSIONS

Measurement of VAI seems to be superior to tVSA in the description of impaired vowel articulation and its further decline in the course of the disease in PD. Since impairment of vowel articulation was found to be independent from global motor function but correlated to gait dysfunction, measurement of vowel articulation might have a potential to serve as a marker of axial disease progression.

Deep brain stimulation of caudal zona incerta and subthalamic nucleus in patients with Parkinson's disease: effects on voice intensity

Deep brain stimulation of the subthalamic nucleus (STN-DBS) in patients with Parkinson's disease (PD) affects speech inconsistently. Recently, stimulation of the caudal zona incerta (cZi-DBS) has shown superior motor outcomes for PD patients, but effects on speech have not been systematically investigated. The aim of this study was to compare the effects of cZi-DBS and STN-DBS on voice intensity in PD patients. Mean intensity during reading and intensity decay during rapid syllable repetition were measured for STN-DBS and cZi-DBS patients (eight patients per group), before- and 12 months after-surgery on- and off-stimulation. For mean intensity, there were small significant differences on- versus off-stimulation in each group: 74.2 (2.0) dB contra 72.1 (2.2) dB (P = .002) for STN-DBS, and 71.6 (4.1) dB contra 72.8 (3.4) dB (P = .03) for cZi-DBS, with significant interaction (P < .001). Intensity decay showed no significant changes. The subtle differences found for mean intensity suggest that STN-DBS and cZi-DBS may influence voice intensity differently.