Predicting Speech Intelligibility Based on Spatial Tongue-Jaw Coupling in Persons With Amyotrophic Lateral Sclerosis: The Impact of Tongue Weakness and Jaw Adaptation

Disease-Specific Speech Movement Characteristics of the Tongue and Jaw

PURPOSE

To advance our understanding of disease-specific articulatory impairment patterns in speakers with dysarthria, this study investigated the articulatory performance of the tongue and jaw in speakers with differing neurological diseases (Parkinson's disease [PD], amyotrophic lateral sclerosis, multiple sclerosis, and Huntington's disease).

METHOD

Fifty-seven speakers with dysarthria and 30 controls produced the sentence "Buy Kaia a kite" five times. A three-dimensional electromagnetic articulography was used to record the articulatory movements of the posterior tongue and jaw. Sentence-length kinematic measures (e.g., duration, tongue range of motion [ROM], jaw ROM, tongue speed, jaw speed) were extracted.

RESULTS

Results revealed significant group effects for the duration, jaw ROM, and tongue speed but not for tongue ROM. Post hoc pairwise comparisons revealed more significant between-groups differences for duration and jaw ROM than for tongue speed. Statistically significant findings between clinical groups were predominantly driven by the difference between speakers with PD and speakers of other clinical groups.

CONCLUSIONS

Reduced jaw ROM and trends toward reduced tongue ROM confirm hypokinesia as a distinguishing motor feature of speakers with PD. However, deviancies in speed or movement duration did not emerge as a distinguishing motor feature for any of the four studied clinical groups. Nevertheless, movement duration, but not movement speed, may be useful to index dysarthria severity.

A multimodal approach to automated hierarchical assessment of bulbar involvement in amyotrophic lateral sclerosis

Introduction

As a hallmark feature of amyotrophic lateral sclerosis (ALS), bulbar involvement leads to progressive declines of speech and swallowing functions, significantly impacting social, emotional, and physical health, and quality of life. Standard clinical tools for bulbar assessment focus primarily on clinical symptoms and functional outcomes. However, ALS is known to have a long, clinically silent prodromal stage characterized by complex subclinical changes at various levels of the bulbar motor system. These changes accumulate over time and eventually culminate in clinical symptoms and functional declines. Detection of these subclinical changes is critical, both for mechanistic understanding of bulbar neuromuscular pathology and for optimal clinical management of bulbar dysfunction in ALS. To this end, we developed a novel multimodal measurement tool based on two clinically readily available, noninvasive instruments-facial surface electromyography (sEMG) and acoustic techniques-to hierarchically assess seven constructs of bulbar/speech motor control at the neuromuscular and acoustic levels. These constructs, including prosody, pause, functional connectivity, amplitude, rhythm, complexity, and regularity, are both mechanically and clinically relevant to bulbar involvement.

Methods

Using a custom-developed, fully automated data analytic algorithm, a variety of features were extracted from the sEMG and acoustic recordings of a speech task performed by 13 individuals with ALS and 10 neurologically healthy controls. These features were then factorized into 10 composite outcome measures using confirmatory factor analysis. Statistical and machine learning techniques were applied to these composite outcome measures to evaluate their reliability (internal consistency), validity (concurrent and construct), and efficacy for early detection and progress monitoring of bulbar involvement in ALS.

Results

The composite outcome measures were demonstrated to (1) be internally consistent and structurally valid in measuring the targeted constructs; (2) hold concurrent validity with the existing clinical and functional criteria for bulbar assessment; and (3) outperform the outcome measures obtained from each constituent modality in differentiating individuals with ALS from healthy controls. Moreover, the composite outcome measures combined demonstrated high efficacy for detecting subclinical changes in the targeted constructs, both during the prodromal stage and during the transition from prodromal to symptomatic stages.

Discussion

The findings provided compelling initial evidence for the utility of the multimodal measurement tool for improving early detection and progress monitoring of bulbar involvement in ALS, which have important implications in facilitating timely access to and delivery of optimal clinical care of bulbar dysfunction.

The association between longitudinal declines in speech sound accuracy and speech intelligibility in speakers with amyotrophic lateral sclerosis

The purpose of this study was to examine how neurodegeneration secondary to amyotrophic lateral sclerosis (ALS) impacts speech sound accuracy over time and how speech sound accuracy, in turn, is related to speech intelligibility. Twenty-one participants with ALS read the Bamboo Passage over multiple data collection sessions across several months. Phonemic and orthographic transcriptions were completed for all speech samples. The percentage of phonemes accurately produced was calculated across each phoneme, sound class (i.e. consonants versus vowels), and distinctive feature (i.e. features involved in Manner of Articulation, Place of Articulation, Laryngeal Voicing, Tongue Height, and Tongue Advancement). Intelligibility was determined by calculating the percentage of words correctly transcribed orthographically by naive listeners. Linear mixed effects models were conducted to assess the decline of each distinctive feature over time and its impact on intelligibility. The results demonstrated that overall phonemic production accuracy had a nonlinear relationship with speech intelligibility and that a subset of features (i.e. those dependent on precise lingual and labial constriction and/or extensive lingual and labial movement) were more important for intelligibility and were more impacted over time than other features. Furthermore, findings revealed that consonants were more strongly associated with intelligibility than vowels, but consonants did not significantly differ from vowels in their decline over time. These findings have the potential to (1) strengthen mechanistic understanding of the physiological constraints imposed by neuronal degeneration on speech production and (2) inform the timing and selection of treatment and assessment targets for individuals with ALS.

Hierarchical Temporal Structuring of Speech: A Multiscale, Multimodal Framework to Inform the Assessment and Management of Neuromotor Speech Disorder

PURPOSE

Hierarchical temporal structuring of speech is the key to multiscale linguistic information transfer toward effective communication. This study investigated and linked the hierarchical temporal cues of the kinematic and acoustic modalities of natural, unscripted speech in neurologically healthy and impaired speakers.

METHOD

Thirteen individuals with amyotrophic lateral sclerosis (ALS) and 10 age-matched healthy controls performed a story-telling task. The hierarchical temporal structure of the speech stimulus was measured by (a) 26 articulatory-kinematic features characterizing the depth, phase synchronization, and coherence of temporal modulation of the tongue tip, tongue body, lower lip, and jaw, at three hierarchically nested timescales corresponding to prosodic stress, syllables, and onset-rime/phonemes, and (b) 25 acoustic features characterizing the parallel aspects of temporal modulation of five critical-spectral-band envelopes. All features were compared between groups. For each aspect of temporal modulation, the contributions of all articulatory features to the parallel acoustic features were evaluated by group.

RESULTS

Generally consistent disease impacts were identified on the articulatory and acoustic features, manifested by reduced modulation depths of most articulators and critical-spectral-band envelopes, primarily at the timescales of syllables and onset-rime/phonemes. For healthy speakers, the strongest articulatory-acoustic relationships were found for (a) jaw and lip, in modulating stress timing, and (b) tongue tip, in modulating the timing relation between onset-rime/phonemes and syllables. For speakers with ALS, the tongue body, tongue tip, and jaw all showed the greatest contributions to modulating syllable timing.

CONCLUSIONS

The observed disease impacts likely reflect reduced entrainment of speech motor activities to finer-grained linguistic events, presumably due to the dynamic constraints of the neuromuscular system. To accommodate these restrictions, speakers with ALS appear to use their residual articulatory motor capacities to accentuate and convey the perceptually most salient temporal cues underpinned by the syllable-centric parsing mechanism. This adaptive strategy has potential implications in managing neuromotor speech disorders.

A Fine-Grained Temporal Analysis of Multimodal Oral Diadochokinetic Performance to Assess Speech Impairment in Amyotrophic Lateral Sclerosis

PURPOSE

This study used a semiautomated fine-grained temporal analysis to extract features of temporal oral diadochokinetic (DDK) performance across multiple modalities and tasks, from neurologically healthy and impaired individuals secondary to amyotrophic lateral sclerosis (ALS). The aims were to (a) delineate temporal oral DDK deficits relating to the neuromotor pathology of ALS and (b) identify the optimal task-feature combinations to detect speech impairment in ALS.

METHOD

Mandibular myoelectric, kinematic, and acoustic data were acquired from 13 individuals with ALS and 10 healthy controls producing three alternating motion rate tasks and one sequential motion rate task. Twenty-seven features were extracted from the multimodal data, characterizing three temporal constructs: duration/rate, variability, and coordination. The disease impacts on these features were assessed across tasks, and the task eliciting the greatest disease-related change was identified for each feature. Such "optimal" task-feature combinations were fed into logistic regression to differentiate individuals with ALS from healthy controls.

RESULTS

Temporal deficits in ALS were characterized by (a) increased duration and variability and reduced coordination of jaw muscle activities, (b) increased duration and variability and altered temporal symmetry of jaw velocity profile, (c) increased muscle-burst-to-peak-velocity duration, and (d) increased motion-to-voice onset duration. These temporal features were differentially affected across tasks. The optimal task-feature combinations, which were further clustered into three composite factors reflecting temporal variability, coarser-grained duration, and finer-grained duration, differentiated ALS from controls with an F1 score of 0.86 (precision = 1.00, recall = 0.75).

CONCLUSIONS

Temporal oral DDK deficits are likely attributed to a hierarchy of interrelated neurophysiological and biomechanical factors associated with the neuromotor pathology of ALS. These deficits, as assessed crossmodally, provide previously unavailable insights into the multifaceted timing impairment of oromotor performance in ALS. The optimal task-feature combinations targeting these deficits show promise as quantitative markers for (early) detection of speech impairment in ALS.

Acoustic Voice Analysis as a Useful Tool to Discriminate Different ALS Phenotypes

Approximately 80-96% of people with amyotrophic lateral sclerosis (ALS) become unable to speak during the disease progression. Assessing upper and lower motor neuron impairment in bulbar regions of ALS patients remains challenging, particularly in distinguishing spastic and flaccid dysarthria. This study aimed to evaluate acoustic voice parameters as useful biomarkers to discriminate ALS clinical phenotypes. Triangular vowel space area (tVSA), alternating motion rates (AMRs), and sequential motion rates (SMRs) were analyzed in 36 ALS patients and 20 sex/age-matched healthy controls (HCs). tVSA, AMR, and SMR values significantly differed between ALS and HCs, and between ALS with prevalent upper (pUMN) and lower motor neuron (pLMN) impairment. tVSA showed higher accuracy in discriminating pUMN from pLMN patients. AMR and SMR were significantly lower in patients with bulbar onset than those with spinal onset, both with and without bulbar symptoms. Furthermore, these values were also lower in patients with spinal onset associated with bulbar symptoms than in those with spinal onset alone. Additionally, AMR and SMR values correlated with the degree of dysphagia. Acoustic voice analysis may be considered a useful prognostic tool to differentiate spastic and flaccid dysarthria and to assess the degree of bulbar involvement in ALS.

Video-Based Facial Movement Analysis in the Assessment of Bulbar Amyotrophic Lateral Sclerosis: Clinical Validation

PURPOSE

Facial movement analysis during facial gestures and speech provides clinically useful information for assessing bulbar amyotrophic lateral sclerosis (ALS). However, current kinematic methods have limited clinical application due to the equipment costs. Recent advancements in consumer-grade hardware and machine/deep learning made it possible to estimate facial movements from videos. This study aimed to establish the clinical validity of a video-based facial analysis for disease staging classification and estimation of clinical scores.

METHOD

Fifteen individuals with ALS and 11 controls participated in this study. Participants with ALS were stratified into early and late bulbar ALS groups based on their speaking rate. Participants were recorded with a three-dimensional (3D) camera (color + depth) while repeating a simple sentence 10 times. The lips and jaw movements were estimated, and features related to sentence duration and facial movements were used to train a machine learning model for multiclass classification and to predict the Amyotrophic Lateral Sclerosis Functional Rating Scale-Revised (ALSFRS-R) bulbar subscore and speaking rate.

RESULTS

The classification model successfully separated healthy controls, the early ALS group, and the late ALS group with an overall accuracy of 96.1%. Video-based features demonstrated a high ability to estimate the speaking rate (adjusted R ² = .82) and a moderate ability to predict the ALSFRS-R bulbar subscore (adjusted R ² = .55).

CONCLUSIONS

The proposed approach based on a 3D camera and machine learning algorithms represents an easy-to-use and inexpensive system that can be included as part of a clinical assessment of bulbar ALS to integrate facial movement analysis with other clinical data seamlessly.

Functional Role of Temporal Patterning of Articulation in Speech Production: A Novel Perspective Toward Global Timing-Based Motor Speech Assessment and Rehabilitation

PURPOSE

This study aimed to (a) relate temporal patterning of articulation to functional speech outcomes in neurologically healthy and impaired speakers, (b) identify changes in temporal patterning of articulation in neurologically impaired speakers, and (c) evaluate how these changes can be modulated by speaking rate manipulation.

METHOD

Thirteen individuals with amyotrophic lateral sclerosis (ALS) and 10 neurologically healthy controls read a sentence 3 times, first at their habitual rate and then at a voluntarily slowed rate. Temporal patterning of articulation was assessed by 24 features characterizing the modulation patterns within (intra) and between (inter) four articulators (tongue tip, tongue body, lower lip, and jaw) at three linguistically relevant, hierarchically nested timescales corresponding to stress, syllable, and onset-rime/phoneme. For Aim 1, the features for the habitual rate condition were factorized and correlated with two functional speech outcomes-speech intelligibility and intelligible speaking rate. For Aims 2 and 3, the features were compared between groups and rate conditions, respectiely.

RESULTS

For Aim 1, the modulation features combined were moderately to strongly correlated with intelligibility (R ² = .51-.53) and intelligible speaking rate (R ² = .63-.73). For Aim 2, intra-articulator modulation was impaired in ALS, manifested by moderate-to-large decreases in modulation depth at all timescales and cross-timescale phase synchronization. Interarticulator modulation was relatively unaffected. For Aim 3, voluntary rate reduction improved several intra-articulator modulation features identified as being susceptible to the disease effect in individuals with ALS.

CONCLUSIONS

Disrupted temporal patterning of articulation, presumably reflecting impaired articulatory entrainment to linguistic rhythms, may contribute to functional speech declines in ALS. These impairments tend to be improved through voluntary rate reduction, possibly by reshaping the temporal template of motor plans to better accommodate the disease-related neuromechanical constraints in the articulatory system. These findings shed light on a novel perspective toward global timing-based motor speech assessment and rehabilitation.

The Cross-Sectional Area of the Middle and Base of the Tongue is Associated with Swallowing-Related Muscle Strength

Muscle strength and function are generally positively correlated with muscle quantity and negatively correlated with muscle quality; however, the tongue shows a unique tendency, different from limb muscles. The relationship between the characteristics of each part of the tongue, muscle strength and function, and systemic factors has been unclear. The aim of the study was to investigate the relationship between cross-sectional area (CSA) and echo intensity (EI) of the middle and base of the tongue and swallowing, articulation function, and body composition. Eighty-nine healthy individuals were included in this cross-sectional study. Swallowing was assessed using tongue pressure (TP) and jaw opening force (JOF) as they indicate swallowing-related muscle strength. Articulation function was evaluated through oral diadochokinesis (ODK). Bioelectrical impedance analysis was performed for body composition. CSAs and EIs of the middle and base of the tongue were measured using ultrasound. Multiple regression analysis was used to examine the relationship between the characteristics of the tongue, swallowing-related muscle strength, and ODK. In multiple regression analysis with TP as the dependent variable, age (β = - 0.22, P < 0.01) and CSA of the middle part (β = 0.02, P < 0.01) were significant explanatory variables. In multiple regression analysis with JOF as the dependent variable, sex (β = - 2.76, P < 0.01) and CSA of the base (β = - 0.004, P < 0.05) were significant explanatory variables. Multiple regression analysis with articulation function as the dependent variable did not yield significant results. The CSA of the tongue is a better indicator of swallowing-related muscle strength than EI. Ultrasonography may be used for assessing swallowing-related muscle strength.

Articulatory Performance in Dysarthria: Using a Data-Driven Approach to Estimate Articulatory Demands and Deficits

This study pursued two goals: (1) to establish range of motion (ROM) demand tiers (i.e., low, moderate, high) specific to the jaw (J), lower lip (LL), posterior tongue (PT), and anterior tongue (AT) for multisyllabic words based on the articulatory performance of neurotypical talkers and (2) to identify demand- and disease-specific articulatory performance characteristics in talkers with amyotrophic lateral sclerosis (ALS) and Parkinson's disease (PD). J, LL, PT, and AT movements of 12 talkers with ALS, 12 talkers with PD, and 12 controls were recorded using electromagnetic articulography. Vertical ROM, average speed, and movement duration were measured. Results showed that in talkers with PD, J and LL ROM were already significantly reduced at the lowest tier whereas PT and AT ROM were only significantly reduced at moderate and high tiers. In talkers with ALS, J ROM was significantly reduced at the moderate tier whereas LL, PT, and AT ROM were only significantly reduced at the highest tier. In both clinical groups, significantly reduced J and LL speeds could already be observed at the lowest tier whereas significantly reduced AT speeds could only be observed at the highest tier. PT speeds were already significantly reduced at the lowest tier in the ALS group but not until the moderate tier in the PD group. Finally, movement duration, but not ROM or speed performance, differentiated between ALS and PD even at the lowest tier. Results suggest that articulatory deficits vary with stimuli-specific motor demands across articulators and clinical groups.

Articulatory Underpinnings of Reduced Acoustic-Phonetic Contrasts in Individuals With Amyotrophic Lateral Sclerosis

PURPOSE

The aim of this study is to identify the articulatory underpinnings of the acoustic-phonetic correlates of functional speech decline in individuals with amyotrophic lateral sclerosis (ALS).

METHOD

Thirteen individuals with varying severities of speech impairment secondary to ALS and 10 neurologically healthy controls speakers read 12 minimal word pairs, targeting the contrasts in the height, advancement, and length of vowels; the manner and place of articulation for consonants and consonant cluster; and liquid and glide approximants, 5 times. Sixteen acoustic features were extracted to characterize the phonetic contrasts of these minimal word pairs. These acoustic features were correlated with a functional speech index-intelligible speaking rate-using penalized regression, based on which the contributive features were identified as the acoustic-phonetic correlates of the functional speech outcome. Articulatory contrasts of the minimal word pairs were characterized by a set of dissimilarity indices derived by the dynamic time warping algorithm, which measured the differences in the displacement and velocity trajectories of tongue tip, tongue dorsum, lower lip, and jaw between the minimal word pairs. The contributive articulatory features to the acoustic-phonetic correlates were identified by penalized regression.

RESULTS

A variety of acoustic-phonetic features were identified as contributing to the functional speech outcome, of which the contrasts in vowel height and advancement, [r]-[l], [r]-[w], and initial cluster-singleton were the most affected in individuals with ALS. Differential articulatory underpinnings were identified for these acoustic-phonetic features. Impairments of these articulatory underpinnings, especially of tongue tip and tongue dorsum velocities and tongue tip displacement, were associated with reduced acoustic-phonetic contrasts of the minimal word pairs, in a context-specific manner.

CONCLUSION

The findings established explanatory relationships between articulatory impairment and the acoustic-phonetic profile of functional speech decline in ALS, providing useful information for developing targeted management strategies to improve and prolong functional speech in individuals with ALS.

Orofacial Muscle Strength across the Dysarthrias

This study compared orofacial muscle strength between normal and dysarthric speakers and across types of dysarthria, and examined correlations between strength and dysarthria severity. Participants included 79 speakers with flaccid, spastic, mixed spastic–flaccid, ataxic, or hypokinetic dysarthria and 33 healthy controls. Maximum pressure generation (Pmax) by the tongue, lips, and cheeks represented strength. Pmax was lower for speakers with mixed spastic–flaccid dysarthria for all tongue and lip measures, as well as for speakers with flaccid or spastic dysarthria for anterior tongue elevation and lip compression. Anterior tongue elevation and cheek compression tended to be lower than normal for the hypokinetic group. Pmax did not differ significantly between controls and speakers with ataxic dysarthria on any measure. Correlations were generally weak between dysarthria severity and orofacial weakness but were stronger in the dysarthria groups with more prominent orofacial weakness. The results generally support predictions that orofacial weakness accompanies flaccid and/or spastic dysarthria but not ataxic dysarthria. The findings support including type of dysarthria as a variable of interest when examining orofacial weakness in motor speech disorders.

Speech intelligibility loss due to amyotrophic lateral sclerosis: the effect of tongue movement reduction on vowel and consonant acoustic features

The purpose of this study was to identify aspects of impaired tongue motor performance that limit the ability to produce distinct speech sounds and contribute to reduced speech intelligibility in individuals with dysarthria secondary to amyotrophic lateral sclerosis (ALS). We analyzed simultaneously recorded tongue kinematic and acoustic data from 22 subjects during three target words (cat, dog, and took). The subjects included 11 participants with ALS and 11 healthy controls from the X-ray microbeam dysarthria database (Westbury, 1994). Novel measures were derived based on the range and speed of relative movement between two quasi-independent regions of the tongue - blade and dorsum - to characterize the global pattern of tongue dynamics. These "whole tongue" measures, along with the range and speed of single tongue regions, were compared across words, groups (ALS vs. control), and measure types (whole tongue vs. tongue blade vs. tongue dorsum). Reduced range and speed of both global and regional tongue movements were found in participants with ALS relative to healthy controls, reflecting impaired tongue motor performance in ALS. The extent of impairment, however, varied across words and measure types. Compared with the regional tongue measures, the whole tongue measures showed more consistent disease-related changes across the target words and were more robust predictors of speech intelligibility. Furthermore, these whole tongue measures were correlated with various word-specific acoustic features associated with intelligibility decline in ALS, suggesting that impaired tongue movement likely contributes to reduced phonetic distinctiveness of both vowels and consonants that underlie speech intelligibility decline in ALS.

Assessment of dysarthria and dysphagia in patients with amyotrophic lateral sclerosis: Review of the current evidence

Bulbar dysfunction is a common presentation of amyotrophic lateral sclerosis (ALS) and significantly impacts quality of life of people with ALS (PALS). The current paper reviews measurements of dysarthria and dysphagia specific to ALS to identify efficient and valid assessment measures. Using such assessment measures will lead to improved management of bulbar dysfunction in ALS. Measures reviewed for dysarthria in PALS are organized into three categories: acoustic, kinematic, and strength. A set of criteria are used to evaluate the effectiveness of the measures' identification of speech impairments, measurement of functional verbal communication, and clinical applicability. Assessments reviewed for dysphagia in PALS are organized into six categories: patient reported outcomes, dietary intake, pulmonary function and airway defense capacity, bulbar function, dysphagia/aspiration screens, and instrumental evaluations. Measurements that have good potential for clinical use are highlighted in both topic areas. Additionally, areas of improvement for clinical practice and research are identified and discussed. In general, no single speech measure fulfilled all the criteria, although a few measures were identified as potential diagnostic tools. Similarly, few objective measures that were validated and replicated with large sample sizes were found for diagnosis of dysphagia in PALS. Importantly, clinical applicability was found to be limited; thus, a collaborative team focused on implementation science would be helpful to improve the clinical uptake of assessments. Overall, the review highlights the need for further development of clinically viable and efficient measurements that use a multidisciplinary approach.

Spatiotemporal Control of Articulation During Speech and Speechlike Tasks in Amyotrophic Lateral Sclerosis

Purpose This study examined the articulatory control of speech and speechlike tasks in individuals with amyotrophic lateral sclerosis (ALS) and neurologically healthy individuals with the aim to identify the most useful set of articulatory features and tasks for assessing bulbar motor involvement in ALS. Method Tongue and jaw kinematics were recorded in 12 individuals with bulbar ALS and 10 healthy controls during a speech task and two speechlike tasks (i.e., alternating motion rate [AMR], sequential motion rate [SMR]). Eight articulatory features were derived for each participant per task, including the range, maximum speed, and acceleration time of tongue and jaw movements as well as the coupling and timing between tongue and jaw movements. The effects of task (i.e., AMR, SMR, speech) and group (i.e., ALS, control) on these articulatory features were evaluated. For each feature, the task that yielded the largest difference between the ALS and control groups was identified. The diagnostic efficacy of these task-specific features was assessed using the receiver operating characteristic analysis; the relation of these task-specific features to a well-established bulbar severity index-speaking rate-was determined using Spearman's rank correlation. Results Seven task-specific articulatory features were identified, including (a) tongue and jaw acceleration time during the AMR task, (b) tongue-jaw coupling during the SMR task, and (c) range of tongue movement, maximum tongue and jaw speed, and temporal lag between tongue and jaw movements during the speech task. Among these features, tongue and jaw acceleration time and their temporal lag showed relatively high accuracy (i.e., 0.83-0.95) in differentiating individuals with ALS from healthy controls. Range of tongue movement and maximum tongue and jaw speed showed significant correlations with speaking rate. Conclusion Findings provided preliminary evidence for the utility of task-specific articulatory measurements as a novel quantitative assessment to detect and predict bulbar motor involvement in ALS.

Development and Validation of a Probe Word List to Assess Speech Motor Skills in Children

Purpose The aim of the study was to develop and validate a probe word list and scoring system to assess speech motor skills in preschool and school-age children with motor speech disorders. Method This article describes the development of a probe word list and scoring system using a modified word complexity measure and principles based on the hierarchical development of speech motor control known as the Motor Speech Hierarchy (MSH). The probe word list development accounted for factors related to word (i.e., motoric) complexity, linguistic variables, and content familiarity. The probe word list and scoring system was administered to 48 preschool and school-age children with moderate-to-severe speech motor delay at clinical centers in Ontario, Canada, and then evaluated for reliability and validity. Results One-way analyses of variance revealed that the motor complexity of the probe words increased significantly for each MSH stage, while no significant differences in the linguistic complexity were found for neighborhood density, mean biphone frequency, or log word frequency. The probe word list and scoring system yielded high reliability on measures of internal consistency and intrarater reliability. Interrater reliability indicated moderate agreement across the MSH stages, with the exception of MSH Stage V, which yielded substantial agreement. The probe word list and scoring system demonstrated high content, construct (unidimensionality, convergent validity, and discriminant validity), and criterion-related (concurrent and predictive) validity. Conclusions The probe word list and scoring system described in the current study provide a standardized method that speech-language pathologists can use in the assessment of speech motor control. It can support clinicians in identifying speech motor difficulties in preschool and school-age children, set appropriate goals, and potentially measure changes in these goals across time and/or after intervention.

Validation of Articulatory Rate and Imprecision Judgments in Speech of Individuals With Amyotrophic Lateral Sclerosis

Purpose Perceptual judgments of articulatory function are commonly used by speech-language pathologists to evaluate articulatory performance in individuals with amyotrophic lateral sclerosis (ALS). The goal of this study was to evaluate the psychometric properties (e.g., reliability, validity) of these perceptual measures to inform their application as part of a comprehensive bulbar assessment tool in ALS. Method Preexisting data from 51 individuals with ALS were obtained from a larger longitudinal study. Five independent raters provided perceptual judgments of articulatory rate and imprecision in a sentence task. Inter- and intrarater reliability of these judgments were assessed. Perceptual ratings were correlated with an acoustic measure of articulatory rate, in syllables per second, obtained from passage-reading recordings. Both perceptual and acoustic measures were correlated with gold-standard kinematic tongue and jaw movement measures, recorded from sentences using electromagnetic articulography. Results The results revealed good inter- and intrarater reliability of perceptual judgments of articulatory function. Strong correlations were observed between perceptual ratings of articulatory rate and imprecision and acoustic measures of articulatory rate and kinematic measures of tongue speed. Conclusions These findings support the clinical application of perceptual judgments of articulatory function as valid and reliable measures of underlying articulatory changes in bulbar ALS. Additional research is needed to understand the responsiveness of these measures to clinical changes in articulatory function in ALS.

Neuromotor Speech Recovery Across Different Behavioral Speech Modifications in Individuals Following Facial Transplantation

Despite signs of facial nerve recovery within a few months following face transplantation, speech deficits persist for years. Behavioral speech modifications (e.g., slower-than-normal speaking rate and increased loudness) have shown promising potential to enhance speech intelligibility in populations with dysarthric speech. However, such evidence-based practice approach is lacking in clinical management of speech in individuals with facial transplantation. Because facial transplantation involves complex craniofacial reconstruction and facial nerve coaptation, it is unknown to what extent individuals with face transplant are capable of adapting their motor system to task-specific articulatory demands. The purpose of this study was to identify the underlying articulatory mechanisms employed by individuals with face transplantation in response to speech modification cues at early and late stages of neuromotor recovery. In addition, we aimed to identify speech modifications that conferred improved speech clarity. Participants were seven individuals who underwent full or partial facial vascularized composite allografts that included lips and muscles of facial animation and were in early (~2 months) or late (~42 months) stages of recovery. Participants produced repetitions of the sentence “Buy Bobby a puppy” in normal, fast, loud, and slow speech modifications. Articulatory movement traces were recorded using a 3D optical motion capture system. Kinematic measures of average speed (mm/s) and range of movement (mm³) were extracted from the lower lip (± jaw) marker. Two speech language pathologists rated speech clarity for each speaker using a visual analog scale (VAS) approach. Results demonstrated that facial motor capacity increased from early to late stages of recovery. While individuals in the early group exhibited restricted capabilities to adjust their motor system based on the articulatory demands of each speech modification, individuals in the late group demonstrated faster speed and larger-than-normal range of movement for loud speech, and slower speed and larger-than-normal range of movement for slow speech. In addition, subjects in both groups showed overreliance on jaw rather than lip articulatory function across all speech modifications, perhaps as a compensatory strategy to optimize articulatory stability and maximize speech function. Finally, improved speech clarity was associated with loud speech in both stages of recovery.

Neuromotor Control of Speech and Speechlike Tasks: Implications From Articulatory Gestures

Purpose

This study aimed to provide a preliminary examination of the articulatory control of speech and speechlike tasks based on a gestural framework and identify shared and task-specific articulatory factors in speech and speechlike tasks.

Method

Ten healthy participants performed two speechlike tasks (i.e., alternating motion rate [AMR] and sequential motion rate [SMR]) and three speech tasks (i.e., reading of “clever Kim called the cat clinic” at the regular, fast, and slow rates) that varied in phonological complexity and rate. Articulatory kinematics were recorded using an electromagnetic kinematic tracking system (Wave, Northern Digital Inc.). Based on the gestural framework for articulatory phonology, the gestures of tongue body and lips were derived from the kinematic data. These gestures were subjected to a fine-grained analysis, which extracted (a) four gestural features (i.e., range of magnitude [ROM], frequency [Freq], acceleration time, and maximum speed [maxSpd]) for the tongue body gesture; (b) three intergestural measures including the peak intergestural coherence (InterCOH), frequency at which the peak intergestural coherence occurs (Freq_InterCOH), and the mean absolute relative phase between the tongue body and lip gestures; and (c) three intragestural (i.e., interarticulator) measures including the peak intragestural coherence (IntraCOH), Freq_IntraCOH, and mean absolute relative phase between the tongue body and the jaw, which are the component articulators that underlie the tongue body gesture. In addition, the performance rate for each task was also derived. The effects of task and sex on all the articulatory and behavioral measures were examined using mixed-design analysis of variance followed by post hoc pairwise comparisons across tasks.

Results

Task had a significant effect on performance rate, ROM, Freq, maxSpd, InterCOH, Freq_InterCOH, IntraCOH, and Freq_IntraCOH. Compared to the speech tasks, the AMR task showed a decrease in ROM and increases in Freq, InterCOH, Freq_InterCOH, IntraCOH, and Freq_IntraCOH. The SMR task showed similar ROM, Freq, maxSpd, InterCOH, and IntraCOH as the fast and regular speech tasks.

Conclusions

The simple phonological structure and demand for rapid syllable rate for the AMR task may elicit a distinct articulatory control mechanism. Despite being a rapid nonsense syllable repetition task, the relatively complex phonological structure of the SMR task appeared to elicit a similar articulatory control mechanism as that of speech production. Based on these shared and task-specific articulatory features between speech and speechlike tasks, the clinical implications for articulatory assessment were discussed.

Patterns of Misidentified Vowels in Individuals With Dysarthria Secondary to Amyotrophic Lateral Sclerosis

Purpose The current study examines the pattern of misidentified vowels produced by individuals with dysarthria secondary to amyotrophic lateral sclerosis (ALS). Method Twenty-three individuals with ALS and 22 typical individuals produced 10 monophthongs in an /h/-vowel-/d/ context. One hundred thirty-five listeners completed a forced-choice vowel identification test. Misidentified vowels were examined in terms of the target vowel categories (front-back; low-mid-high) and the direction of misidentification (the directional pattern when the target vowel was misidentified, e.g., misidentification "to a lower vowel"). In addition, acoustic predictors of vowel misidentifications were tested based on log first formant (F1), log second formant, log F1 vowel inherent spectral change, log second formant vowel inherent spectral change, and vowel duration. Results First, high and mid vowels were more frequently misidentified than low vowels for all speaker groups. Second, front and back vowels were misidentified at a similar rate for both the Mild and Severe groups, whereas back vowels were more frequently misidentified than front vowels in typical individuals. Regarding the direction of vowel misidentification, vowel errors were mostly made within the same backness (front-back) category for all groups. In addition, more errors were found toward a lower vowel category than toward a higher vowel category in the Severe group, but not in the Mild group. Overall, log F1 difference was identified as a consistent acoustic predictor of the main vowel misidentification pattern. Conclusion Frequent misidentifications in the vowel height dimension and the acoustic predictor, F1, suggest that limited tongue height control is the major articulatory dysfunction in individuals with ALS. Clinical implications regarding this finding are discussed.

Automated Acoustic Analysis of Oral Diadochokinesis to Assess Bulbar Motor Involvement in Amyotrophic Lateral Sclerosis

Purpose The purpose of this article was to validate a novel acoustic analysis of oral diadochokinesis (DDK) in assessing bulbar motor involvement in amyotrophic lateral sclerosis (ALS). Method An automated acoustic DDK analysis was developed, which filtered out the voice features and extracted the envelope of the acoustic waveform reflecting the temporal pattern of syllable repetitions during an oral DDK task (i.e., repetitions of /tɑ/ at the maximum rate on 1 breath). Cycle-to-cycle temporal variability (cTV) of envelope fluctuations and syllable repetition rate (sylRate) were derived from the envelope and validated against 2 kinematic measures, which are tongue movement jitter (movJitter) and alternating tongue movement rate (AMR) during the DDK task, in 16 individuals with bulbar ALS and 18 healthy controls. After the validation, cTV, sylRate, movJitter, and AMR, along with an established clinical speech measure, that is, speaking rate (SR), were compared in their ability to (a) differentiate individuals with ALS from healthy controls and (b) detect early-stage bulbar declines in ALS. Results cTV and sylRate were significantly correlated with movJitter and AMR, respectively, across individuals with ALS and healthy controls, confirming the validity of the acoustic DDK analysis in extracting the temporal DDK pattern. Among all the acoustic and kinematic DDK measures, cTV showed the highest diagnostic accuracy (i.e., 0.87) with 80% sensitivity and 94% specificity in differentiating individuals with ALS from healthy controls, which outperformed the SR measure. Moreover, cTV showed a large increase during the early disease stage, which preceded the decline of SR. Conclusions This study provided preliminary validation of a novel automated acoustic DDK analysis in extracting a useful measure, namely, cTV, for early detection of bulbar ALS. This analysis overcame a major barrier in the existing acoustic DDK analysis, which is continuous voicing between syllables that interferes with syllable structures. This approach has potential clinical applications as a novel bulbar assessment.