Assessing Oromotor Capacity in ALS: The Effect of a Fixed-Target Task on Lip Biomechanics

This work is licensed under a Creative Commons Attribution 4.0 International License.Alternating motion rate (AMR) is a standard measure often included in neurological examinations to assess orofacial neuromuscular integrity. AMR is typically derived from recordings of patients producing repetitions of a single syllable as fast and clear as possible on one breath. Because the task places high demands on oromotor performance, particularly articulatory speed, AMRs are widely considered to be tests of maximum performance and, therefore, likely to reveal underlying neurologic deficits. Despite decades of widespread use, biomechanical studies have shown that speakers often circumvent the presumed speed challenge of the standard AMR task. Specifically, speakers are likely to manipulate their displacements (movement amplitude) instead of speed because this strategy requires less motor effort. The current study examined the effectiveness of a novel fixed-target paradigm for minimizing the truncation of articulatory excursions and maximizing motor effort. We compared the standard AMR task to that of a fixed-target AMR task and focused specifically on the tasks' potential to detect decrements in lip motor performance in persons with dysarthria due to amyotrophic lateral sclerosis (ALS). Our participants were 14 healthy controls and 17 individuals with ALS. For the standard AMR task, participants were instructed to produce the syllable /bα/ as quickly and accurately as possible on one breath. For the fixed-target AMR task, participants were given the same instructions, but were also required to strike a physical target placed under the jaw during the opening phase of each syllable. Lip kinematic data were obtained using 3D electromagnetic articulography. 16 kinematic features were extracted using an algorithmic approach. Findings revealed that compared to the standard task, the fixed-target AMR task placed increased motor demands on the oromotor system by eliciting larger excursions, faster speeds, and greater spatiotemporal variability. In addition, participants with ALS exhibited limited ability to adapt to the higher articulatory demands of the fixed-target task. Between the two AMR tasks, the maximum speed during the fixed-target task showed a moderate association with the ALSFRS-R bulbar subscore. Employment of both standard and fixed-target AMR tasks is, however, needed for comprehensive assessment of oromotor function and for elucidating profiles of task adaptation

Predicting Speech Intelligibility Decline in Amyotrophic Lateral Sclerosis Based on the Deterioration of Individual Speech Subsystems

This research was supported by the following grants: National Institute of Health— National Institute of Deafness and Other Communication Disorders (http://www.nidcd.nih.gov/Pages/default.aspx) Grants R01 DC009890 & R01 DC0135470 (PI: JG); ALS Society of Canada (https://www.als.ca/en) Denise Ramsay Discovery Grant (PI:YY); Canadian Institute of Health Research (http:// www.cihr-irsc.gc.ca/e/47631.html) CIHR Planning Grant FRN126682 (PI: YY). The funders had no role n study design, data collection and analysis, decision to publish, or preparation of the manuscript.Purpose: To determine the mechanisms of speech intelligibility impairment due to neurologic impairments, intelligibility decline was modeled as a function of co-occurring changes in the articulatory, resonatory, phonatory, and respiratory subsystems. Method: Sixty-six individuals diagnosed with amyotrophic lateral sclerosis (ALS) were studied longitudinally. The disease-related changes in articulatory, resonatory, phonatory, and respiratory subsystems were quantified using multiple instrumental measures, which were subjected to a principal component analysis and mixed effects models to derive a set of speech subsystem predictors. A stepwise approach was used to select the best set of subsystem predictors to model the overall decline in intelligibility. Results: Intelligibility was modeled as a function of five predictors that corresponded to velocities of lip and jaw movements (articulatory), number of syllable repetitions in the alternating motion rate task (articulatory), nasal airflow (resonatory), maximum fundamental frequency (phonatory), and speech pauses (respiratory). The model accounted for 95.6% of the variance in intelligibility, among which the articulatory predictors showed the most substantial independent contribution (57.7%). Conclusion: Articulatory impairments characterized by reduced velocities of lip and jaw movements and resonatory impairments characterized by increased nasal airflow served as the subsystem predictors of the longitudinal decline of speech intelligibility in ALS. Declines in maximum performance tasks such as the alternating motion rate preceded declines in intelligibility, thus serving as early predictors of bulbar dysfunction. Following the rapid decline in speech intelligibility, a precipitous decline in maximum performance tasks subsequently occurred

Modeling of oropharyngeal articulatory adaptation to compensate for the acoustic effects of nasalization

Hypernasality is one of the most detrimental speech disturbances that lead to declines of speech intelligibility. Velopharyngeal inadequacy, which is associated with anatomic defects such as cleft palate or neuromuscular disorders that affect velopharygneal function, is the primary cause of hypernasality. A simulation study by Rong and Kuehn [J. Speech Lang. Hear. Res. 55(5), 1438–1448 (2012)] demonstrated that properly adjusted oropharyngeal articulation can reduce nasality for vowels synthesized with an articulatory model [Mermelstein, J. Acoust. Soc. Am. 53(4), 1070–1082 (1973)]. In this study, a speaker-adaptive articulatory model was developed to simulate speaker-customized oropharyngeal articulatory adaptation to compensate for the acoustic effects of nasalization on /a/, /i/, and /u/. The results demonstrated that (1) the oropharyngeal articulatory adaptation effectively counteracted the effects of nasalization on the second lowest formant frequency (F2) and partially compensated for the effects of nasalization on vowel space (e.g., shifting and constriction of vowel space) and (2) the articulatory adaptation strategies generated by the speaker-adaptive model might be more efficacious for counteracting the acoustic effects of nasalization compared to the adaptation strategies generated by the standard articulatory model in Rong and Kuehn. The findings of this study indicated the potential of using oropharyngeal articulatory adaptation as a means to correct maladaptive articulatory behaviors and to reduce nasalit

Using articulatory adjustment to compensate for hypernasality - a modeling study based on measures of electromagnetic articulography (EMA)

The speech of individuals with velopharyngeal incompetency (VPI) is characterized by hypernasality, a speech quality related to excessive emission of acoustic energy through the nose, as caused by failure of velopharyngeal closure. As an attempt to reduce hypernasality and, in turn, improve the quality of VPI-related hypernasal speech, this study is dedicated to developing an approach that uses speech-dependent articulatory adjustments to reduce hypernasality caused by excessive velopharyngeal opening. A preliminary study has been done to derive such articulatory adjustments for hypernasal /i/ vowels based on the simulation of an articulatorymodel (Speech Processing and Synthesis Toolboxes, Childers (2000)). Both nasal /i/ vowels with and without articulatory adjustments were synthesized by the model. Spectral analysis found that nasal acoustic features were attenuated and oral formant structures were restored after articulatory adjustments. In addition, comparisons of perceptual ratings of nasality between the two types of nasal vowels showed the articulatory adjustments generated by the model significantly reduced the perception of nasality for nasal /i/ vowels. Such articulatory adjustments for nasal /i/ have two patterns: 1) a consistent adjustment pattern, which corresponds an expansion at the velopharynx, and 2) some speech-dependent fine-tuning adjustment patterns, including adjustments in the lip area and the upper pharynx. The long-term goal of this study is to apply this approach of articulatory adjustment as a therapeutic tool in clinical speech treatment to detect and correct the maladaptive articulatory behaviors developed spontaneously by speakers with VPI on individual bases. This study constructed a speaker-adaptive articulatory model on the basis of the framework of Childers’s vocal tract model to simulate articulatory adjustments aiming at compensating for the acoustic outcome caused by velopharyngeal opening and reducing nasality. To construct such a speaker-adaptive articulatory model, (1) an articulatory-acoustic-aerodynamic database was recorded using the articulography and aerodynamic instruments to provide point-wise articulatory data to be fitted into the framework of Childers’s standard vocal tract model; (2) the length and transverse dimension of the vocal tract were adjusted to fit individual speaker by minimizing the acoustic discrepancy between the model simulation and the target derived from acoustic signal in the database using the simulated annealing algorithm; (3) the articulatory space of the model was adjusted to fit individual articulatory features by adapting the movement ranges of all articulators. With the speaker-adaptive articulatory model, the articulatory configurations of the oral and nasal vowels in the database were simulated and synthesized. Given the acoustic targets derived from the oral vowels in the database, speech-dependent articulatory adjustments were simulated to compensate for the acoustic outcome caused by VPO. The resultant articulatory configurations corresponds to nasal vowels with articulatory adjustment, which were synthesized to serve as the perceptual stimuli for a listening task of nasality rating. The oral and nasal vowels synthesized based on the oral and nasal vowel targets in the database also served as the perceptual stimuli. The results suggest both acoustic and perceptual effects of the mode-generated articulatory adjustment on the nasal vowels /a/, /i/ and /u/. In terms of acoustics, the articulatory adjustment (1) restores the altered formant structures due to nasal coupling, including shifted formant frequency, attenuated formant intensity and expanded formant bandwidth and (2) attenuates the peaks and zeros caused by nasal resonances. Perceptually, the articulatory adjustment generated by the speaker-adaptive model significantly reduces the perceived nasality for all three vowels (/a/, /i/, /u/). The acoustic and perceptual effects of articulatory adjustment suggest achievement of the acoustic goal of compensating for the acoustic discrepancy caused by VPO and the auditory goal of reducing the perception of nasality. Such a finding is consistent with motor equivalence (Hughes and Abbs, 1976; Maeda, 1990), which enables inter-articulator coordination to compensate for the deviation from the acoustic/auditory goal caused by the shifted position of an articulator. The articulatory adjustment responsible for the acoustic and perceptual effects as described above was decomposed into a set of empirical orthogonal modes (Story and Titze, 1998). Both gross articulatory patterns and fine-tuning adjustments were found in the principal orthogonal modes, which lead to the acoustic compensation and reduction of nasality. For /a/ and /i/, a direct relationship was found among the acoustic features, nasality, and articulatory adjustment patterns. Specifically, the articulatory adjustments indicated by the principal orthogonal modes of the adjusted nasal /a/ and /i/ were directly correlated with the attenuation of the acoustic cues of nasality (i.e., shifting of F1 and F2 frequencies) and the reduction of nasality rating. For /u/, such a direct relationship among the acoustic features, nasality and articulatory adjustment was not as prominent, suggesting the possibility of additional acoustic correlates of nasality other than F1 and F2. The findings of this study demonstrate the possibility of using articulatory adjustment to reduce the perception of nasality through model simulation. A speaker-adaptive articulatory model is able to simulate individual-based articulatory adjustment strategies that can be applied in clinical settings to serve as the articulatory targets for correction of the maladaptive articulatory behaviors developed spontaneously by speakers with hypernasal speech. Such a speaker-adaptive articulatory model provides an intuitive way of articulatory learning and self-training for speakers with VPI to learn appropriate articulatory strategies through model-speaker interaction

Managing the distinctiveness of phonemic nasal vowels : articulatory evidence from Hindi

There is increasing evidence that fine articulatory adjustments are made by speakers to reinforce and sometimes counteract the acoustic consequences of nasality. However, it is difficult to attribute the acoustic changes in nasal vowel spectra to either oral cavity configuration or to velopharyngeal opening (VPO). This paper takes the position that it is possible to disambiguate the effects of VPO and oropharyngeal configuration on the acoustic output of the vocal tract by studying the position and movement of the tongue and lips during the production of oral and nasal vowels. This paper uses simultaneously collected articulatory, acoustic, and nasal airflow data during the production of all oral and phonemically nasal vowels in Hindi (four speakers) to understand the consequences of the movements of oral articulators on the spectra of nasal vowels. For Hindi nasal vowels, the tongue body is generally lowered for back vowels, fronted for low vowels, and raised for front vowels (with respect to their oral congeners). These movements are generally supported by accompanying changes in the vowel spectra. In Hindi, the lowering of back nasal vowels may have originally served to enhance the acoustic salience of nasality, but has since engendered a nasal vowel chain shift

The relationship between velopharyngeal opening and place of Articulation : an aerodynamic and EPG investigation

A combination of aerodynamic and EPG instrumentation is used to estimate the relationship between velopharyngeal opening (VPO) and linguopalatal place of articulation for a variety of oral and nasal speech sounds. VPO values, estimated using the pressure-flow technique, are generally consistent with the results of previous aerodynamic studies, though smaller than values from imaging studies. The relationship between VPO and linguopalatal contact anteriority differs across consonants with different places of articulation. For velars, linguopalatal contact is more posterior with increased VPO, while bilabials manifest the opposite pattern. This finding may be related to the interaction between velar nasals and nasal vowels suggested in previous studies

Compensatory articulation in American English nasalized vowels

In acoustic studies of vowel nasalization, it is sometimes assumed that the primary articulatory difference between an oral vowel and a nasal vowel is the coupling of the nasal cavity to the rest of the vocal tract. Acoustic modulations observed in nasal vowels are customarily attributed to the presence of additional poles affiliated with the naso-pharyngeal tract and zeros affiliated with the nasal cavity. We test the hypothesis that oral configuration may also change during nasalized vowels, either enhancing or compensating for the acoustic modulations associated with nasality. We analyze tongue position, nasal airflow, and acoustic data to determine whether American English /i/ and /a/ manifest different oral configurations when they are nasalized, i.e. when they are followed by nasal consonants. We find that tongue position is higher during nasalized [ĩ] than it is during oral [i] but do not find any effect for nasalized [ã]. We argue that speakers of American English raise the tongue body during nasalized [ĩ] in order to counteract the perceived F1-raising (centralization) associated with high vowel nasalization

Predicting Early Bulbar Decline in Amyotrophic Lateral Sclerosis: A Speech Subsystem Approach

Purpose. To develop a predictive model of speech loss in persons with amyotrophic lateral sclerosis (ALS) based on measures of respiratory, phonatory, articulatory, and resonatory functions that were selected using a data-mining approach. Method. Physiologic speech subsystem (respiratory, phonatory, articulatory, and resonatory) functions were evaluated longitudinally in 66 individuals with ALS using multiple instrumentation approaches including acoustic, aerodynamic, nasometeric, and kinematic. The instrumental measures of the subsystem functions were subjected to a principal component analysis and linear mixed effects models to derive a set of comprehensive predictors of bulbar dysfunction. These subsystem predictors were subjected to a Kaplan-Meier analysis to estimate the time until speech loss. Results. For a majority of participants, speech subsystem decline was detectible prior to declines in speech intelligibility and speaking rate. Among all subsystems, the articulatory and phonatory predictors were most responsive to early bulbar deterioration; and the resonatory and respiratory predictors were as responsive to bulbar decline as was speaking rate. Conclusions. The articulatory and phonatory predictors are sensitive indicators of early bulbar decline due to ALS, which has implications for predicting disease onset and progression and clinical management of ALS

Predicting Early Bulbar Decline in Amyotrophic Lateral Sclerosis: A Speech Subsystem Approach

Purpose. To develop a predictive model of speech loss in persons with amyotrophic lateral sclerosis (ALS) based on measures of respiratory, phonatory, articulatory, and resonatory functions that were selected using a data-mining approach. Method. Physiologic speech subsystem (respiratory, phonatory, articulatory, and resonatory) functions were evaluated longitudinally in 66 individuals with ALS using multiple instrumentation approaches including acoustic, aerodynamic, nasometeric, and kinematic. The instrumental measures of the subsystem functions were subjected to a principal component analysis and linear mixed effects models to derive a set of comprehensive predictors of bulbar dysfunction. These subsystem predictors were subjected to a Kaplan-Meier analysis to estimate the time until speech loss. Results. For a majority of participants, speech subsystem decline was detectible prior to declines in speech intelligibility and speaking rate. Among all subsystems, the articulatory and phonatory predictors were most responsive to early bulbar deterioration; and the resonatory and respiratory predictors were as responsive to bulbar decline as was speaking rate. Conclusions. The articulatory and phonatory predictors are sensitive indicators of early bulbar decline due to ALS, which has implications for predicting disease onset and progression and clinical management of ALS.Peer Reviewe