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Purpose: This study examines the efficacy of perceptual training for improving typical listeners' identification of vowels produced by individuals with dysarthria. We examined whether training on a subset of vowels can generalize to (a) untrained vowels and (b) other speakers with similar overall intelligibility. Method: Sixty naive listeners completed a pretest/posttest perceptual learning task. In the pretraining test and posttraining test, participants identified nine American English monophthongs produced by two speakers with dysarthria secondary to amyotrophic lateral sclerosis (ALS). In the 20-min training task, a two-alternative forced choice (2AFC) task with feedback trained listeners on a subset of the vowels and speakers presented in the pretraining test. Results: Vowel identification accuracy improved overall as a function of training. However, patterns of generalization between speakers and vowel types were not symmetric. Specifically, listeners generalized training from front vowels to back vowels but not vice versa. Likewise, listeners generalized from one speaker to another but not in the opposite direction. Examination of confusion matrices for the pretraining and posttraining revealed complex patterns of vowel-specific improvement. Conclusions: This study demonstrates that listeners benefit from a very simple training paradigm targeting vowels. Additionally, error patterns revealed that vowels are both resistant to and responsive to perceptual learning. Implications for future research and clinical training paradigms are discussed.

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.

Purpose: We present a tripartite view of intelligibility in which the contributions of both the speaker and listener, as well as their joint effort during interaction, are considered. While considerable research has examined communicative interactions in situ, there is a critical gap in current knowledge on how speech intelligibility unfolds during such interactions. Here, we argue that research examining speech intelligibility in communicative interactions may provide important groundwork for advancement in clinical interventions for individuals with dysarthria. Method: First, we describe the view and argue for its consideration as a powerful way of thinking about speech intelligibility. We then briefly situate the view in the relevant literature on speech intelligibility and existing theoretical frameworks. We then identify suitable methodological paradigms for studying joint contributions to intelligibility and, lastly, discuss the clinical application and potential impact of this tripartite view. Conclusions: Speech communication occurs through interaction; however, in the laboratory and clinic, emphasis is usually placed on individual speakers and listeners. We have proposed that it is critical to consider how the joint contributions of speakers and listeners affect speech intelligibility in communicative interaction. This conceptualization is well aligned with the International Classification of Functioning, Disability and Health, and the findings from such an approach will allow us to better understand how to maximize available resources to enhance speech intelligibility.

Purpose: The current study tested jaw movement characteristics and their impact on tongue movement for speech production in individuals with amyotrophic lateral sclerosis (ALS). Specifically, the study examined tongue and jaw movement in multiple directions during jaw opening and closing strokes in individuals with ALS and controls. Method: Twenty-two individuals with ALS and 22 controls participated in the current study. Tongue and jaw movements during the production of the words "Iowa" and "Ohio" (produced in a carrier phrase) were recorded using electromagnetic articulography. Tongue and jaw distances were measured for jaw opening and closing strokes. Distance was measured in the anterior--posterior and superior--inferior dimensions (retraction, advancement, lowering, and raising). Results: Findings revealed that individuals with ALS exaggerated their jaw opening movements, but not their jaw closing movements, compared to controls. Between the groups, a comparable tongue lowering distance was observed during jaw opening movements. In contrast, reduced tongue raising was observed during the jaw closing movements in individuals with ALS compared to controls. Conclusion: The findings suggest that individuals with ALS produce excessive jaw opening movements in the absence of excessive jaw closing movements. The lack of excessive jaw closing movements results in reduced tongue raising in these individuals. Excessive jaw opening movements alone suggest a direction-specific jaw dysfunction. Future studies should examine whether excessive jaw raising can be facilitated and if it enhances tongue raising movement for speech production in individuals with dysarthria secondary to ALS.

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 /?/ than /[epsilon]/, unlike individuals with mild dysarthria and typically aging individuals. In addition, vowel intelligibility of /?/ 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 /?/ 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 /?/. Overall, the vowel-specific intelligibility pattern is related to both vowel-specific characteristics and group-specific articulatory control dysfunction.

Purpose: Speech acoustic characteristics of children with cerebral palsy (CP) were examined with a multiple speech subsystems approach; speech intelligibility was evaluated using a prediction model in which acoustic measures were selected to represent three speech subsystems. Method: Nine acoustic variables reflecting different subsystems, and speech intelligibility, were measured in 22 children with CP. These children included 13 with a clinical diagnosis of dysarthria (speech motor impairment [SMI] group) and 9 judged to be free of dysarthria (no SMI [NSMI] group). Data from children with CP were compared to data from age-matched typically developing children. Results: Multiple acoustic variables reflecting the articulatory subsystem were different in the SMI group, compared to the NSMI and typically developing groups. A significant speech intelligibility prediction model was obtained with all variables entered into the model (adjusted R[superscript 2] = 0.801). The articulatory subsystem showed the most substantial independent contribution (58%) to speech intelligibility. Incremental R[superscript 2] analyses revealed that any single variable explained less than 9% of speech intelligibility variability. Conclusions: Children in the SMI group had articulatory subsystem problems as indexed by acoustic measures. As in the adult literature, the articulatory subsystem makes the primary contribution to speech intelligibility variance in dysarthria, with minimal or no contribution from other systems.

Purpose: In this study, the authors proposed and tested a preliminary speech and language classification system for children with cerebral palsy. Method: Speech and language assessment data were collected in a laboratory setting from 34 children with cerebral palsy (CP; 18 male, 16 female) with a mean age of 54 months (SD = 1.8). Measures of interest were vowel area, speech rate, language comprehension scores, and speech intelligibility ratings. Results: Canonical discriminant function analysis showed that 3 functions accounted for 100% of the variance among profile groups, with speech variables accounting for 93% of the variance. Classification agreement varied from 74% to 97% based on 4 different classification paradigms. Conclusions: The results of this study provide preliminary support for the classification of speech and language abilities of children with CP into 4 initial profile groups. Further research is necessary to validate the full classification system.

Purpose: This study examined the effect of alphabet supplementation (AS) on temporal and spectral features of speech production in individuals with cerebral palsy and dysarthria. Method: Twelve speakers with dysarthria contributed speech samples using habitual speech and while using AS. One hundred twenty listeners orthographically transcribed speech samples. Differences between habitual and AS speech were examined for intelligibility, rate, word duration, vowel duration, pause duration, pause frequency, vowel space, and first and second formant frequency (F1 and F2) values for corner vowels. Results: Descriptive results showed that intelligibility was higher, rate of speech was slower, and pause duration and pause frequency were greater for AS than for habitual speech. Inferential statistics showed that vowel duration, word duration, and vowel space increased significantly for AS. Vowel space did not differ for male and female speakers; however, there was an interaction between sex and speaking condition. Changes in vowel space were accomplished by reductions in F2 for /u/. Vowel space accounted for more variability in intelligibility than rate for AS; the opposite was true for habitual speech. Conclusion: AS is associated with temporal and spectral changes in speech production. Spectral changes associated with corner vowels appear to be more important than temporal changes.