Influences of electromagnetic articulography sensors on speech produced by healthy adults and individuals with aphasia and apraxia

Differential spectral characteristics of the Spanish fricative /s/ in the articulation of individuals with dysarthria and apraxia of speech

PURPOSE

This study examines whether there are differences in the speech of speakers with dysarthria, speakers with apraxia and healthy speakers in spectral acoustic measures during production of the central-peninsular Spanish alveolar sibilant fricative /s/.

METHOD

To this end, production of the sibilant was analyzed in 20 subjects with dysarthria, 8 with apraxia of speech and 28 healthy speakers. Participants produced 12 sV(C) words. The variables compared across groups were the fricative's spectral amplitude difference (AmpD) and spectral moments in the temporal midpoint of fricative execution.

RESULTS

The results indicate that individuals with dysarthria can be distinguished from healthy speakers in terms of the spectral characteristics AmpD, standard deviation (SD), center of gravity (CoG) and skewness, the last two in context with unrounded vowel, while no differences in kurtosis were detected. Participants with AoS group differ significantly from healthy speaker group in AmpD, SD and CoG and Kurtosis, the first one followed unrounded vowel and the latter two followed by rounded vowels. In addition, speakers with apraxia of speech group returned significant differences with respect to speakers with dysarthria group in AmpD, CoG and skewness.

CONCLUSIONS

The differences found between the groups in the measures studied as a function of the type of vowel context could provide insights into the distinctive manifestations of motor speech disorders, contributing to the differential diagnosis between apraxia and dysarthria in motor control processes.

Evaluation of a Wireless Tongue Tracking System on the Identification of Phoneme Landmarks

OBJECTIVE

Evaluate the accuracy of a tongue tracking system based on the localization of a permanent magnet to generate a baseline of phoneme landmarks. The positional variability of the landmarks provides an indirect measure of the tracking errors to estimate the position of a small tracer attached on the tongue. The creation of a subject-independent (universal) baseline was also attempted for the first time.

METHOD

2,500 tongue trajectories were collected from 10 subjects tasked to utter 10 repetitions of 25 phonemes. A landmark was identified from each tongue trajectory, and tracking errors were calculated by comparing the distance of each repetition landmark to a final landmark set as their mean position.

RESULTS

In the subject-dependent baseline, the tracking errors were found to be generally consistent across all phonemes, and subjects, with less than 25% of the errors reported to be greater than 5.8 mm (median: 3.9 mm). However, the inter-subject variability showed that current limitations of our system resulted in appreciable errors (median: 55 mm, Q3: 65 mm).

CONCLUSION

The tracking errors reported in the subject-dependent case demonstrated the potential of our system to generate a baseline of phoneme landmarks. We have identified areas of improvement that will reduce the gap between the subject-dependent, and universal baseline, while lowering tracking errors to be comparable to the gold standard.

SIGNIFICANCE

Creating a baseline of phoneme landmarks can help people affected by speech sound disorders to improve their intelligibility using visual feedback that guides their tongue placement to the proper position.

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.

Vowel-Specific Intelligibility and Acoustic Patterns in Individuals With Dysarthria Secondary to Amyotrophic Lateral Sclerosis

Purpose The purpose of the study was to investigate vowel-specific intelligibility and acoustic patterns of individuals with different severities of dysarthria secondary to amyotrophic lateral sclerosis (ALS). Method Twenty-three individuals with dysarthria secondary to ALS and 22 typically aging individuals participated as speakers. Participants with ALS were divided into 2 severity groups (severe, mild). For vowel-specific intelligibility data, 135 listeners participated in the study. Vowel-specific intelligibility, intrinsic vowel duration, 1st and 2nd formants (F1 and F2), vowel inherent spectral change (VISC), and absolute VISC were examined. Results A significant interaction between severity group and the vowel-specific intelligibility pattern as well as F1, F2 VISC, and absolute F2 VISC was observed. Specifically, individuals with severe dysarthria showed a significantly less intelligible /ɪ/ than /ɛ/, unlike individuals with mild dysarthria and typically aging individuals. In addition, vowel intelligibility of /ɪ/ showed the strongest association to the severity measures in individuals with ALS. A number of vowel-specific findings are reported in the acoustic variables. Acoustic correlates of vowel-specific intelligibility were identified. Conclusion Vowel-specific intelligibility patterns are different across severity groups; particularly, low intelligibility of /ɪ/ was noted in individuals with severe dysarthria. Individuals with dysarthria maintained the acoustic contrast in duration and F1 VISC among vowels but did not maintain the other spectral contrasts. Reduction of acoustic vowel space was observed primarily due to high F1 in high vowels in individuals with severe dysarthria. Regression findings suggest that the high F1 values of high and mid vowels and F2 reduction of high- and mid-front vowels decreased vowel-specific intelligibility. In addition, vowel duration influenced the vowel intelligibility of vowels that required short intrinsic vowel duration. Lastly, F2 VISC influenced the vowel intelligibility of /ɪ/. Overall, the vowel-specific intelligibility pattern is related to both vowel-specific characteristics and group-specific articulatory control dysfunction.

Interventions for childhood apraxia of speech

BACKGROUND

Childhood apraxia of speech (CAS) affects a child's ability to produce sounds and syllables precisely and consistently, and to produce words and sentences with accuracy and correct speech rhythm. It is a rare condition, affecting only 0.1% of the general population. Consensus has been reached that three core features have diagnostic validity: (1) inconsistent error production on both consonants and vowels across repeated productions of syllables or words; (2) lengthened and impaired coarticulatory transitions between sounds and syllables; and (3) inappropriate prosody (ASHA 2007). A deficit in motor programming or planning is thought to underlie the condition. This means that children know what they would like to say but there is a breakdown in the ability to programme or plan the fine and rapid movements required to accurately produce speech. Children with CAS may also have impairments in one or more of the following areas: non-speech oral motor function, dysarthria, language, phonological production impairment, phonemic awareness or metalinguistic skills and literacy, or combinations of these. High-quality evidence from randomised controlled trials (RCTs) is lacking on interventions for CAS.

OBJECTIVES

To assess the efficacy of interventions targeting speech and language in children and adolescents with CAS as delivered by speech and language pathologists/therapists.

SEARCH METHODS

We searched CENTRAL, MEDLINE, Embase, eight other databases and seven trial registers up to April 2017. We searched the reference lists of included reports and requested information on unpublished trials from authors of published studies and other experts as well as information groups in the areas of speech and language therapy/pathology and linguistics.

SELECTION CRITERIA

RCTs and quasi-RCTs of children aged 3 to 16 years with CAS diagnosed by a speech and language pathologist/therapist, grouped by treatment types.

DATA COLLECTION AND ANALYSIS

Two review authors (FL, AM) independently assessed titles and abstracts identified from the searches and obtained full-text reports of all potentially relevant articles and assessed these for eligibility. The same two authors extracted data and conducted the 'Risk of bias' and GRADE assessments. One review author (EM) tabulated findings from excluded observational studies (Table 1).

MAIN RESULTS

This review includes only one RCT, funded by the Australian Research Council; the University of Sydney International Development Fund; Douglas and Lola Douglas Scholarship on Child and Adolescent Health; Nadia Verrall Memorial Scholarship; and a James Kentley Memorial Fellowship. This study recruited 26 children aged 4 to 12 years, with mild to moderate CAS of unknown cause, and compared two interventions: the Nuffield Dyspraxia Programme-3 (NDP-3); and the Rapid Syllable Transitions Treatment (ReST). Children were allocated randomly to one of the two treatments. Treatments were delivered intensively in one-hour sessions, four days a week for three weeks, in a university clinic in Australia. Speech pathology students delivered the treatments in the English language. Outcomes were assessed before therapy, immediately after therapy, at one month and four months post-therapy. Our review looked at one-month post-therapy outcomes only.We judged all core outcome domains to be low risk of bias. We downgraded the quality of the evidence by one level to moderate due to imprecision, given that only one RCT was identified. Both the NDP-3 and ReST therapies demonstrated improvement at one month post-treatment. A number of cases in each cohort had recommenced usual treatment by their speech and language pathologist between one month and four months post-treatment (NDP-3: 9/13 participants; ReST: 9/13 participants). Hence, maintenance of treatment effects to four months post-treatment could not be analysed without significant potential bias, and thus this time point was not included for further analysis in this review.There is limited evidence that, when delivered intensively, both the NDP-3 and ReST may effect improvement in word accuracy in 4- to 12-year-old children with CAS, measured by the accuracy of production on treated and non-treated words, speech production consistency and the accuracy of connected speech. The study did not measure functional communication.

AUTHORS' CONCLUSIONS

There is limited evidence that, when delivered intensively, both the NDP-3 and ReST may effect improvement in word accuracy in 4- to 12-year-old children with CAS, measured by the accuracy of production on treated and non-treated words, speech production consistency and the accuracy of connected speech. The study did not measure functional communication. No formal analyses were conducted to compare NDP-3 and ReST by the original study authors, hence one treatment cannot be reliably advocated over the other. We are also unable to say whether either treatment is better than no treatment or treatment as usual. No evidence currently exists to support the effectiveness of other treatments for children aged 4 to 12 years with idiopathic CAS without other comorbid neurodevelopmental disorders. Further RCTs replicating this study would strengthen the evidence base. Similarly, further RCTs are needed of other interventions, in other age ranges and populations with CAS and with co-occurring disorders.

Speech Adaptation to Kinematic Recording Sensors: Perceptual and Acoustic Findings

PURPOSE

This study used perceptual and acoustic measures to examine the time course of speech adaptation after the attachment of electromagnetic sensor coils to the tongue, lips, and jaw.

METHOD

Twenty native English speakers read aloud stimulus sentences before the attachment of the sensors, immediately after attachment, and again 5, 10, 15, and 20 min later. They read aloud continuously between recordings to encourage adaptation. Sentence recordings were perceptually evaluated by 20 native English listeners, who rated 150 stimuli (which included 31 samples that were repeated to assess rater reliability) using a visual analog scale with the end points labeled as "precise" and "imprecise." Acoustic analysis began by segmenting and measuring the duration of the fricatives /s/ and /ʃ/ as well as the whole sentence. The spectral center of gravity and spectral standard deviation of the 2 fricatives were measured using Praat. These phonetic targets were selected because the standard placement of sensor coils on the lingual surface was anticipated to interfere with normal fricative production, causing them to become distorted.

RESULTS

Perceptual ratings revealed a decrease in speech precision after sensor attachment and evidence of adaptation over time; there was little perceptual change beyond the 10-min recording. The spectral center of gravity for /s/ decreased, and the spectral standard deviation for /ʃ/ increased after sensor attachment, but the acoustic measures showed no evidence of adaptation over time.

CONCLUSION

The findings suggest that 10 min may be sufficient time to allow speakers to adapt before experimental data collection with Northern Digital Instruments Wave electromagnetic sensors.

Multimodal Speech Capture System for Speech Rehabilitation and Learning

Speech-language pathologists (SLPs) are trained to correct articulation of people diagnosed with motor speech disorders by analyzing articulators' motion and assessing speech outcome while patients speak. To assist SLPs in this task, we are presenting the multimodal speech capture system (MSCS) that records and displays kinematics of key speech articulators, the tongue and lips, along with voice, using unobtrusive methods. Collected speech modalities, tongue motion, lips gestures, and voice are visualized not only in real-time to provide patients with instant feedback but also offline to allow SLPs to perform post-analysis of articulators' motion, particularly the tongue, with its prominent but hardly visible role in articulation. We describe the MSCS hardware and software components, and demonstrate its basic visualization capabilities by a healthy individual repeating the words "Hello World." A proof-of-concept prototype has been successfully developed for this purpose, and will be used in future clinical studies to evaluate its potential impact on accelerating speech rehabilitation by enabling patients to speak naturally. Pattern matching algorithms to be applied to the collected data can provide patients with quantitative and objective feedback on their speech performance, unlike current methods that are mostly subjective, and may vary from one SLP to another.

Characterizing Articulation in Apraxic Speech Using Real-Time Magnetic Resonance Imaging

Purpose

Real-time magnetic resonance imaging (MRI) and accompanying analytical methods are shown to capture and quantify salient aspects of apraxic speech, substantiating and expanding upon evidence provided by clinical observation and acoustic and kinematic data. Analysis of apraxic speech errors within a dynamic systems framework is provided and the nature of pathomechanisms of apraxic speech discussed.

Method

One adult male speaker with apraxia of speech was imaged using real-time MRI while producing spontaneous speech, repeated naming tasks, and self-paced repetition of word pairs designed to elicit speech errors. Articulatory data were analyzed, and speech errors were detected using time series reflecting articulatory activity in regions of interest.

Results

Real-time MRI captured two types of apraxic gestural intrusion errors in a word pair repetition task. Gestural intrusion errors in nonrepetitive speech, multiple silent initiation gestures at the onset of speech, and covert (unphonated) articulation of entire monosyllabic words were also captured.

Conclusion

Real-time MRI and accompanying analytical methods capture and quantify many features of apraxic speech that have been previously observed using other modalities while offering high spatial resolution. This patient's apraxia of speech affected the ability to select only the appropriate vocal tract gestures for a target utterance, suppressing others, and to coordinate them in time.

Multimodal acquisition of articulatory data: Geometrical and temporal registration

Acquisition of dynamic articulatory data is of major importance for studying speech production. It turns out that one technique alone often is not enough to get a correct coverage of the whole vocal tract at a sufficient sampling rate. Ultrasound (US) imaging has been proposed as a good acquisition technique for the tongue surface because it offers a good temporal sampling, does not alter speech production, is cheap, and is widely available. However, it cannot be used alone and this paper describes a multimodal acquisition system which uses electromagnetography sensors to locate the US probe. The paper particularly focuses on the calibration of the US modality which is the key point of the system. This approach enables US data to be merged with other data. The use of the system is illustrated via an experiment consisting of measuring the minimal tongue to palate distance in order to evaluate and design Magnetic Resonance Imaging protocols well suited for the acquisition of three-dimensional images of the vocal tract. Compared to manual registration of acquisition modalities which is often used in acquisition of articulatory data, the approach presented relies on automatic techniques well founded from geometrical and mathematical points of view.

Toward a quantitative basis for assessment and diagnosis of apraxia of speech

PURPOSE

We explored the reliability and validity of 2 quantitative approaches to document presence and severity of speech properties associated with apraxia of speech (AOS).

METHOD

A motor speech evaluation was administered to 39 individuals with aphasia. Audio-recordings of the evaluation were presented to 3 experienced clinicians to determine AOS diagnosis and to rate severity of 11 speech dimensions. Additionally, research assistants coded 11 operationalized metrics of articulation, fluency, and prosody in the same speech samples and in recordings from 20 neurologically healthy participants.

RESULTS

Agreement among the 3 clinicians was limited for both AOS diagnosis and perceptual scaling, but inter-observer reliability for the operationalized metrics was strong. The relationships between most operationalized metrics and mean severity ratings for corresponding perceptual dimensions were moderately strong and statistically significant. Both perceptual scaling and operationalized quantification approaches were sensitive to the presence or absence of AOS.

CONCLUSIONS

Perceptual scaling and operationalized metrics are promising quantification techniques that can help establish diagnostic transparency for AOS. However, because satisfactory reliability cannot be assumed for scaling techniques, effective training and calibration procedures should be implemented. Operationalized metrics show strong potential for enhancing diagnostic objectivity and sensitivity.

Articulatory and acoustic adaptation to palatal perturbation

Previous work has established that speakers have difficulty making rapid compensatory adjustments in consonant production (especially in fricatives) for structural perturbations of the vocal tract induced by artificial palates with thicker-than-normal alveolar regions. The present study used electromagnetic articulography and simultaneous acoustic recordings to estimate tongue configurations during production of [s š t k] in the presence of a thin and a thick palate, before and after a practice period. Ten native speakers of English participated in the study. In keeping with previous acoustic studies, fricatives were more affected by the palate than were the stops. The thick palate lowered the center of gravity and the jaw was lower and the tongue moved further backwards and downwards. Center of gravity measures revealed complete adaptation after training, and with practice, subjects' decreased interlabial distance. The fact that adaptation effects were found for [k], which are produced with an articulatory gesture not directly impeded by the palatal perturbation, suggests a more global sensorimotor recalibration that extends beyond the specific articulatory target.

Is /h/ phonetically neutral?

Use of /h/ in the phrase, 'Say /hVC/ again' has been tacitly assumed to provide a neutral phonetic context in which to study the articulatory characteristics of speech either preceding or following /h/ articulation. Yet, assessment of the stability or neutrality of /h/ has gone untested. The current study sought to determine whether articulation of /h/ differs according to sex and language accent, as well as to examine its influence on subsequent vowel articulation. Selected acoustic features of /hVC/ were measured in 40 speakers of American English (AE) and 40 speakers of Mandarin-accented English (MAE). Results of an analysis of /h/ duration revealed no sex differences within each language group, however considerable variation was found according to accented vs unaccented English. Clear sex differences were found for the production of /h/, occurring more often among male speakers regardless of language variety. Considerable variation in production of /h/ was found between language groups. Analysis of vowel formant frequencies immediately following /h/ articulation indicated minimal coarticulatory effects for both AE and MAE speakers. The present results appear to support the suggestion that /h/ is not exclusively sex-linked and may indeed vary according to non-biological factors. In spite of these variations, /h/ articulation appears to have a negligible influence on neighbouring vowel articulation.

Intervention for childhood apraxia of speech

BACKGROUND

The diagnostic criteria for Childhood Apraxia of Speech (CAS), and the underlying cause(s) for this disorder, remain heavily debated. Some agreement exists that children with CAS may have impairments in one or more of the following domains: non-speech oral motor function, motor speech function, speech sounds and structures (i.e., syllable and word shapes), prosody, language, phonemic awareness / metalinguistic skills, and literacy . Recently consensus has been reached that only three features across these domains have diagnostic validity: (1) inconsistent error production on both consonants and vowels across repeated productions of syllables or words, (2) lengthened and impaired coarticulatory transitions between sounds and syllables, and (3) inappropriate prosody (ASHA 2007). Perhaps due to the ongoing deliberation over aetiology and diagnosis, little evidence on intervention for CAS is published.

OBJECTIVES

To assess the efficacy of intervention delivered by Speech and Language Pathologists(s)/Speech and Language Therapists targeting CAS in children and adolescents.

SEARCH STRATEGY

The following databases were searched: CENTRAL (Issue 4, 2006), MEDLINE (1966 to 01/2007), CINAHL (1982 to 12/2006), EMBASE (1980 to 01/2007), ERIC (1965 to 01/2007), Linguistics Abstracts Online (1985 to 01/2007), PsycINFO (1872 to 01/2007). Reference lists of articles thus identified were examined.

SELECTION CRITERIA

The review considered randomised controlled trials (RCTs) and quasi-randomised studies of children aged 3 to 16 years with CAS, grouped by treatment types (e.g., perceptual and instrumentally-based biofeedback treatment techniques).

DATA COLLECTION AND ANALYSIS

Two authors independently assessed titles and abstracts identified from the searches and obtained full text versions of all potentially relevant articles. Articles were assessed for design and risk of bias. In addition to outcome data, a range of variables about participant group and outcomes were documented.

MAIN RESULTS

Of 825 titles and abstracts searched, only 31 abstracts appeared to meet inclusion criteria. The remaining 794 papers were excluded predominantly on the basis of not including participants with CAS (e.g., focused on other developmental speech disorders or adult acquired apraxia of speech), or for not being intervention studies (i.e. being diagnostic or descriptive). All 31 full text articles obtained were excluded following evaluation as they did not meet inclusion criteria on design. . Thus no studies are included in this review.

AUTHORS' CONCLUSIONS

The review demonstrates a critical lack of well controlled treatment studies addressing treatment efficacy for CAS, making it impossible for conclusions to be drawn about which interventions are most effective for treating CAS in children or adolescents.