Speech production in Parkinson's disease: I. An electropalatographic investigation of tongue-palate contact patterns

Oral-diadochokinesis between Parkinson's disease and neurotypical elderly among Malaysian-Malay speakers

BACKGROUND

Parkinson's disease (PD) has an impact on speech production, manifesting in various ways including alterations in voice quality, challenges in articulating sounds and a decrease in speech rate. Numerous investigations have been conducted to ascertain the oral-diadochokinesis (O-DDK) rate in individuals with PD. However, the existing literature lacks exploration of such O-DDK rates in Malaysia and does not provide consistent evidence regarding the advantage of real-word repetition.

AIMS

To explore the effect of gender, stimuli type and PD status and their interactions on the O-DDK rates among Malaysian-Malay speakers.

METHODS & PROCEDURES

O-DDK performance of 62 participants (29 individuals with PD and 33 healthy elderly) using a non-word ('pataka'), a Malay real-word ('patahkan') and an English real-word ('buttercake') was audio recorded. The number of syllables produced in 8 s was counted. A hierarchical linear modelling was performed to investigate the effects of stimuli type (non-word, Malay real-word, English real-word), PD status (yes, no), gender (male, female) and their interactions on the O-DDK rate. The model accounted for participants' age as well as the nesting of repeated measurements within participants, thereby providing unbiased estimates of the effects.

OUTCOMES & RESULTS

The stimuli effect was significant (p < 0.0001). Malay real-word showed the lowest O-DDK rate (5.03 ± 0.11 syllables/s), followed by English real-word (5.25 ± 0.11 syllables/s) and non-word (5.42 ± 0.11 syllables/s). Individuals with PD showed a significantly lower O-DDK rate compared to healthy elderly (4.73 ± 0.15 syllables/s vs. 5.74 ± 0.14 syllables/s, adjusted p < 0.001). A subsequent analysis indicated that the O-DDK rate declined in a quadratic pattern. However, neither gender nor age effects were observed. Additionally, no significant two-way interactions were found between stimuli type, PD status and gender (all p > 0.05). Therefore, the choice of stimuli type has no or only limited effect considering the use of O-DDK tests in clinical practice for diagnostic purposes.

CONCLUSIONS & IMPLICATIONS

The observed slowness in O-DDK among individuals with PD can be attributed to the impact of the movement disorder, specifically bradykinesia, on the physiological aspects of speech production. Speech-language pathologists can gain insights into the impact of PD on speech production and tailor appropriate intervention strategies to address the specific needs of individuals with PD according to disease stages.

WHAT THIS PAPER ADDS

What is already known on this subject The observed slowness in O-DDK rates among individuals with PD may stem from the movement disorder's effects on the physiological aspects of speech production, particularly bradykinesia. However, there is a lack of consistent evidence regarding the influence of real-word repetition and how O-DDK rates vary across different PD stages. What this study adds to existing knowledge The O-DDK rates decline in a quadratic pattern as the PD progresses. The research provides insights into the advantage of real-word repetition in assessing O-DDK rates, with Malay real-word showing the lowest O-DDK rate, followed by English real-word and non-word. What are the potential or actual clinical implications of this work? Speech-language pathologists can better understand the evolving nature of speech motor impairments as PD progresses. This insight enables them to design targeted intervention strategies that are sensitive to the specific needs and challenges associated with each PD stage. This finding can guide clinicians in selecting appropriate assessment tools for evaluating speech motor function in PD patients.

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.

Speech Rate Mediated Vowel and Stop Voicing Distinctiveness in Parkinson's Disease

Purpose The purpose of this study was to quantify changes in acoustic distinctiveness in two groups of talkers with Parkinson's disease as they modify across a wide range of speaking rates. Method People with Parkinson's disease with and without deep brain stimulation and older healthy controls read 24 carrier phrases at different speech rates. Target nonsense words in the carrier phrases were designed to elicit stop consonants and corner vowels. Participants spoke at seven self-selected speech rates from very slow to very fast, elicited via magnitude production. Speech rate was measured in absolute words per minute and as a proportion of each talker's habitual rate. Measures of segmental distinctiveness included a temporal consonant measure, namely, voice onset time, and a spectral vowel measure, namely, vowel articulation index. Results All talkers successfully modified their rate of speech from slow to fast. Talkers with Parkinson's disease and deep brain stimulation demonstrated greater baseline speech impairment and produced smaller proportional changes at the fast end of the continuum. Increasingly slower speaking rates were associated with increased temporal contrasts (voice onset time) but not spectral contrasts (vowel articulation). Faster speech was associated with decreased contrasts in both domains. Talkers with deep brain stimulation demonstrated more aberrant productions across all speaking rates. Conclusions Findings suggest that temporal and spectral segmental distinctiveness are asymmetrically affected by speaking rate modifications in Parkinson's disease. Talkers with deep brain stimulation warrant further investigation with regard to speech changes they make as they adjust their speaking rate.

Single Word Intelligibility of Individuals with Parkinson's Disease in Noise: Pre-Specified Secondary Outcome Variables from a Randomized Control Trial (RCT) Comparing Two Intensive Speech Treatments (LSVT LOUD vs. LSVT ARTIC)

The majority of people with Parkinson's disease (PD) experience both prosodic changes (reduced vocal volume, reduced pitch range) and articulatory changes (imprecise articulation) that often limit speech intelligibility and may contribute to significant declines in quality of life. We conducted a randomized control trial comparing two intensive treatments, voice (LSVT LOUD) or articulation (LSVT ARTIC) to assess single word intelligibility in the presence of background noise (babble and mall). Participants (64 PD and 20 Healthy) read words from the diagnostic rhyme test (DRT), an ANSI Standard for measuring intelligibility of speech, before and after one month (treatment or no treatment). Teams of trained listeners blindly rated the data. Speech intelligibility of words in the presence of both noise conditions improved in PD participants who had LSVT LOUD compared to the groups that had LSVT ARTIC or no treatment. Intensive speech treatment targeting prominent prosodic variables in LSVT LOUD had a positive effect on speech intelligibility at the single word level in PD.

Characterizing the distribution of silent intervals in the connected speech of individuals with Parkinson disease

The purpose of the current investigation was to examine a statistical approach to differentiating shorter silent intervals (e.g., stop gaps) from longer silent intervals (e.g., pause) at varying syntactic locations within a reading passage to better characterize articulatory and prosodic aspects of speech timing in Parkinson disease (PD). Silent intervals 15 ms and longer were extracted from reading sample. Logarithmic transformation of the silent interval durations yielded a bimodal distribution. Gaussian Mixture Model analysis was used to statistically differentiate the first mode (Mode 1) that corresponded to short silent intervals from the second mode (Mode 2) that corresponded to longer silent intervals. The syntactic context surrounding each silent interval was also categorized. Results revealed that the large majority of silent intervals that occurred within a clause, phrase, or word were assigned to Mode 1, while the majority of silent intervals that coincided with sentence-ending punctuation were assigned to Mode 2. Results revealed that Mode 1 intervals were slightly, but significantly longer for speakers with PD (Mean = 52.48 ms, SE = 3.23) compared to controls (Mean = 44.67 ms, SE = 2.00). Examination of the surrounding syntactic context revealed that this difference occurred at between-word boundaries contained within a phrase or clause. No between group differences were observed for the other inter- and intra-sentence syntactic boundaries or Mode 2 intervals. This study outlines a data-based approach to differentiating short between- and within-word intervals from longer silent intervals or pauses that reflect the prosodic and syntactic structure of a reading passage. Using this approach, the current data suggest that speakers with PD exhibit longer short silent intervals than controls, potentially reflecting a slight delay in the fluent segment-to-segment transition between words.

Rhythmic performance in hypokinetic dysarthria: Relationship between reading, spontaneous speech and diadochokinetic tasks

•We investigated speech rhythm in people with Parkinson’s Disease (PwPD) and controls. •Even mildly affected PwPD differed from controls in their rhythmic performance. •PwPD showed less difference between reading and spontaneous speech. •Spontaneous speech highlighted more differences between speakers than reading. •DDK performance did not relate to rhythmic behaviour in connected speech.

Is there an order of loss of sounds in speakers with Parkinson's disease?

Influential reports on speech changes in people with Parkinson's disease (PD; Logemann et al., 1978, 1981) reported a posterior to anterior pattern of loss of speech sound accuracy. These claims have never been examined. In a partial replication of Logemann et al.'s work, we examined whether posterior lingual sounds are most affected in people with Parkinson's disease, followed by anterior lingual sounds and then labial sounds. Ninety-nine people with PD (age: mean 70.7, SD 8.46; time since diagnosis: mean 6.97, SD 6.2) with mild to severe overall motor symptoms (Hoehn and Yahr stages 1-5, median 2.5) completed a diagnostic intelligibility test. This was scored by 60 listeners unfamiliar with PD and dysarthric speech. We calculated the proportion of posterior versus anterior lingual versus labial sounds misrecognized by the listeners. We compared profiles of misperceived sounds within and across Hoehn and Yahr stages of severity and in relation to Unified Parkinson's Disease Rating Scale (UPDRS) and speech intelligibility scores. Speech accuracy declined significantly in relation to overall motor impairment for labial and anterior lingual sounds but not for velar sounds. Speech sound accuracy was strongly associated with intelligibility outcomes (p = < 0.01). Contrary to previous assertions, there was no evidence supporting the existence of a posterior to anterior order of 'loss' of oral speech sounds in people with PD, nor an interaction of anterior-posterior speech profile changes with Hoehn and Yahr stage. Findings support the notion that a common underlying impairment of movement downscaling affects all sounds similarly and simultaneously in PD from the start.

Automatic Detection of Phone-Based Anomalies in Dysarthric Speech

Perceptual evaluation is still the most common method in clinical practice for diagnosing and following the progression of the condition of people with speech disorders. Although a number of studies have addressed the acoustic analysis of speech productions exhibiting impairments, additional descriptive analysis is required to manage interperson variability, considering speakers with the same condition or across different conditions. In this context, this article investigates automatic speech processing approaches dedicated to the detection and localization of abnormal acoustic phenomena in speech signal produced by people with speech disorders. This automatic process aims at enhancing the manual investigation of human experts while at the same time reducing the extent of their intervention by calling their attention to specific parts of the speech considered as atypical from an acoustical point of view.

Two different approaches are proposed in this article. The first approach models only the normal speech, whereas the second models both normal and dysarthric speech. Both approaches are evaluated following two strategies: one consists of a strict phone comparison between a human annotation of abnormal phones and the automatic output, while the other uses a “one-phone delay” for the comparison.

The experimental evaluation of both approaches for the task of detecting acoustic anomalies was conducted on two different corpora composed of French dysarthric speakers and control speakers. These approaches obtain very encouraging results and their potential for clinical uses with different types of dysarthria and neurological diseases is quite promising.

Speech-related fatigue and fatigability in Parkinson's disease

This study tested the assumption that speech is more susceptible to fatigue than normal in persons with dysarthria. After 1 h of speech-like exercises, participants with Parkinson's disease (PD) were expected to report increased perceptions of fatigue and demonstrate fatigability by producing less precise speech with corresponding acoustic changes compared to neurologically normal participants. Twelve adults with idiopathic PD and 13 neurologically normal adults produced sentences with multiple lingual targets before and after six 10-min blocks of fast syllable or word productions. Both groups reported increasing self-perceived fatigue over time, but trained listeners failed to detect systematic differences in articulatory precision or speech naturalness between sentences produced before and after speech-related exercises. Similarly, few systematic acoustic differences occurred. These findings do not support the hypothesis that dysarthric speakers are particularly susceptible to speech-related fatigue; instead, speech articulation generally appears to be resistant to fatigue induced by an hour of moderate functional exercises.

Presence of stop bursts and multiple bursts in individuals with Parkinson disease

Studies have reported that individuals with Parkinson Disease (PD) have imprecise articulation of stop consonants due to either slowness of articulators or decreased closure strength. The moment of release for stop consonants, called the burst, has been previously studied in individuals with PD and in other disorders. Multiple bursts (MBs) on the same stop consonant have been reported previously in some motor speech disorders, but no studies are known to have examined MBs in individuals with PD. The current study looked at the occurrences of bursts and MBs in initial stop consonants produced by nine individuals with PD (ON and OFF medication) and nine control speakers. Individuals with PD produced fewer overall bursts compared to control participants. In terms of place of articulation, individuals with PD primarily had loss of bursts in bilabial stops. In addition, individuals with PD had more MBs than control speakers, primarily in alveolars. Finally, no dopamine-related medication effects were found for occurrences of bursts or MBs in individuals with PD. Overall, the study provided evidence for loss of bursts and presence of MBs for stop consonants produced by individuals with PD.

Articulatory closure proficiency in patients with Parkinson's disease following deep brain stimulation of the subthalamic nucleus and caudal zona incerta

PURPOSE

The present study aimed at comparing the effects of deep brain stimulation (DBS) treatment of the subthalamic nucleus (STN) and the caudal zona incerta (cZi) on the proficiency in achieving oral closure and release during plosive production of people with Parkinson's disease.

METHOD

Nineteen patients participated preoperatively and 12 months after DBS surgery. Nine patients had implantations in the STN, 7 bilaterally and 2 unilaterally (left). Ten had bilateral implantations in the cZi. Postoperative examinations were made off and on stimulation. All patients received simultaneous L-dopa treatment in all conditions. For a series of plosives extracted from a reading passage, absolute and relative measures of duration of frication and amplitude of plosive release were compared between conditions within each treatment group.

RESULTS

Relative duration of frication increased in voiceless plosives in the on-stimulation condition in cZi patients. Similar trends were observed across the data set. Duration of prerelease frication and the release peak prominence increased in voiceless plosives on stimulation for both groups.

CONCLUSION

The increased release prominence suggests that patients achieved a stronger closure gesture because of DBS but that the increased energy available resulted in increased frication.

Effect of speaker age on speech recognition and perceived listening effort in older adults with hearing loss

PURPOSE

Older adults exhibit difficulty understanding speech that has been experimentally degraded. Age-related changes to the speech mechanism lead to natural degradations in signal quality. We tested the hypothesis that older adults with hearing loss would exhibit declines in speech recognition when listening to the speech of older adults, compared with the speech of younger adults, and would report greater amounts of listening effort in this task.

METHOD

Nineteen individuals with age-related hearing loss completed speech recognition and listening effort scaling tasks. Both were conducted in quiet, when listening to high- and low-predictability phrases produced by younger and older speakers, respectively.

RESULTS

No significant difference in speech recognition existed when stimuli were derived from younger or older speakers. However, perceived effort was significantly higher when listening to speech from older adults, as compared with younger adults.

CONCLUSIONS

For older individuals with hearing loss, natural degradations in signal quality may require greater listening effort. However, they do not interfere with speech recognition-at least in quiet. Follow-up investigation of the effect of speaker age on speech recognition and listening effort under more challenging noise conditions appears warranted.

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.

Effects of medication and subthalamic nucleus deep brain stimulation on tongue movements in speakers with Parkinson's disease using electropalatography: a pilot study

Parkinson's disease (PD) affects speech in the majority of patients. Subthalamic nucleus deep brain stimulation (STN-DBS) is particularly effective in reducing tremor and rigidity. However, its effect on speech is variable. The aim of this pilot study was to quantify the effects of bilateral STN-DBS and medication on articulation, using electropalatography (EPG). Two patients, PT1 and PT2, were studied under four conditions: on and off medication and ON and OFF stimulation. The EPG protocol consisted of a number of target words with alveolar and velar stops, repeated 10 times in random order. The motor part III of the Unified Parkinson Disease Rating Scale (UPDRS) indicated significantly improved motor scores in the ON stimulation condition in both patients. However, PT1's articulation patterns deteriorated with stimulation whereas PT2 showed improving articulatory accuracy in the same condition. The results revealed different effects of stimulation and medication on articulation particularly with regard to timing. The study quantified less articulatory undershoot for velar stops in comparison to alveolars. Furthermore, the findings provided preliminary evidence that stimulation with medication has a more detrimental effect on articulation than stimulation without medication.

Kinematic analysis of lingual function in dysarthric speakers with Parkinson's disease: An electromagnetic articulograph study

Dysarthria in people with Parkinson's disease (PD) has been widely studied. However, a limited number of studies have investigated lingual function during speech production in this population. This study aimed to investigate lingual kinematics during speech production using electromagnetic articulography (AG-200 EMA). The PD group consisted of eight dysarthric speakers with PD and was matched with a group of eight controls. The tongue tip and tongue back movements of all participants during sentence production were recorded by EMA. Results showed that, perceptually, the participants with PD were mildly dysarthric. Kinematic results documented comparable (for alveolar sentence production) and increased (for velar sentence production) range of lingual movement in the PD group when compared to the control group. Lingual movement velocity, acceleration, and deceleration were also increased in the PD group, predominantly for the release phase of consonant production during sentence utterances. The PD group had longer duration in the production of alveolar consonant and comparable duration in the production of velar consonant. The results of the present study suggest the presence of impaired lingual control in individuals with PD. Increased range of articulatory movement, primarily in the release phase of consonant production, may account for articulatory imprecision in this population.

Acoustic and perceptual analysis of speech adaptation to an artificial palate

The study investigated adaptation to a standard electropalatographic (EPG) practise palate in a group of eight adults (mean age = 24 years). The participants read the phrase "a CVC" over four sampling conditions: prior to inserting the palate, immediately following insertion of the palate, 45 minutes after palate insertion, and 3 hours after insertion of the palate. Perceptual and acoustic analyses were conducted on the initial CV portion of the stimuli. Consonants examined included: /t/, /k/, /s/, and // followed by the /i/, /a/, and /u/ vowels. Results revealed that individuals within the group were able to adapt their speech articulation to compensate for the presence of the artificial palate. Perceptually, mild consonant imprecision was observed upon insertion of the palate; however, this resolved following 45 minutes to 3 hours of adaptation. Acoustic findings indicated that the palate did not affect segment durations or vowel formant frequencies. However, a significant reduction in M1 for /s/ persisted across the sampling periods. Overall, the results suggest that a period of between 45 minutes and 3 hours of adaptation is generally suitable for participation in EPG studies.

Effects of intensive voice treatment (the Lee Silverman Voice Treatment [LSVT]) on vowel articulation in dysarthric individuals with idiopathic Parkinson disease: acoustic and perceptual findings

PURPOSE

To evaluate the effects of intensive voice treatment targeting vocal loudness (the Lee Silverman Voice Treatment [LSVT]) on vowel articulation in dysarthric individuals with idiopathic Parkinson's disease (PD).

METHOD

A group of individuals with PD receiving LSVT (n = 14) was compared to a group of individuals with PD not receiving LSVT (n = 15) and a group of age-matched healthy individuals (n = 14) on the variables vocal sound pressure level (VocSPL); various measures of the first (F1) and second (F2) formants of the vowels /i/, /u/, and /a/; vowel triangle area; and perceptual vowel ratings. The vowels were extracted from the words key, stew, and Bobby embedded in phrases. Perceptual vowel rating was performed by trained raters using a visual analog scale.

RESULTS

Only VocSPL, F2 of the vowel /u/ (F2u), and the ratio F2i/F2u significantly differed between patients and healthy individuals pretreatment. These variables, along with perceptual vowel ratings, significantly changed (improved) in the group receiving LSVT only.

CONCLUSION

These results, along with previous findings, add further support to the generalized therapeutic impact of intensive voice treatment on orofacial functions (speech, swallowing, facial expression) and respiratory and laryngeal functions in individuals with PD.

The Degenerative Dysarthrias: A Window into Critical Clinical and Research Issues

Although diversity of symptoms and urgency of needs pose many challenges, management of the degenerative dysarthrias is a crucial aspect of clinical practice. The purpose of this article is to review current research literature on selected degenerative dysarthrias including those associated with Parkinson's disease, multiple sclerosis, and amyotrophic lateral sclerosis. These dysarthrias are prevalent yet represent distinct patterns of underlying neuropathology, symptoms, age of onset, and rate of progression. Literature searches including the period 1997-2006 yielded 148 different studies reporting data on communication issues related to dysarthria. By far the largest category of studies was that which provided a basic description of speech production including the neurophysiologic, acoustic, or perceptual properties of dysarthria. Other categories included management (assessment and treatment) and the psychosocial consequences of dysarthria. While the topic of management of degenerative dysarthria is a focused one, it provides a window into many issues critical to the field of communication disorders including fundamental properties of speech production, development of evidence-based treatment techniques, the staging of these techniques into an effective management sequence, and the psychosocial consequences of communication disorders along with techniques to maintain communicative participation in the face of degenerative conditions.

Adaptation to an electropalatograph palate: acoustic, impressionistic, and perceptual data

PURPOSE

The purpose of this study was to evaluate adaptation to the electropalatograph (EPG) from the perspective of consonant acoustics, listener perceptions, and speaker ratings.

METHOD

Seven adults with typical speech wore an EPG and pseudo-EPG palate over 2 days and produced syllables, read a passage, counted, and rated their adaptation to the palate. Consonant acoustics, listener ratings, and speaker ratings were analyzed.

RESULTS

The spectral mean for the burst (/t/) and frication (/s/) was reduced for the first 60-120 min of wearing the pseudo-EPG palate. Temporal features (stop gap, frication, and syllable duration) were unaffected by wearing the pseudo-EPG palate. The EPG palate had a similar effect on consonant acoustics as the pseudo-EPG palate. Expert listener ratings indicated minimal to no change in speech naturalness or distortion from the pseudo-EPG or EPG palate. The sounds [see text] were most likely to be affected. Speaker self-ratings related to oral comfort, speech, tongue movement, appearance, and oral sensation were negatively affected by the presence of the palatal devices.

CONCLUSIONS

Speakers detected a substantial difference when wearing a palatal device, but the effects on speech were minimal based on listener ratings. Spectral features of consonants were initially affected, although adaptation occurred. Wearing an EPG or pseudo-EPG palate for approximately 2 hr results in relatively normal-sounding speech with acoustic features similar to a no-palate condition.