Examining speech motor planning difficulties in apraxia of speech and aphasia via the sequential production of phonetically similar words

Stability Over Time of Word Syllable Duration for Speakers With Acquired Apraxia of Speech

PURPOSE

Neurogenic speech and language disorders-such as acquired apraxia of speech (AOS) and aphasia with phonemic paraphasia (APP)-are often misdiagnosed due to similarities in clinical presentation. Word syllable duration (WSD)-a measure of average syllable length in multisyllabic words-serves as a proxy for speech rate, which is an important and arguably more objective clinical characteristic of AOS and APP. This study reports stability of WSD over time for speakers with AOS (and aphasia).

METHOD

Twenty-nine participants with AOS and aphasia (11 women and 18 men, Mage = 53.5 years, SD = 13.3) repeated 30 multisyllabic words (of three-, four-, and five-syllable lengths) on three occasions across 4 weeks. WSDs were calculated for each word and then averaged across each list (i.e., word length), as well as across combined lists (i.e., all 30 words) to yield four WSDs for each participant at each time point. Stability over time was calculated using Friedman's test for the group and using Spearman's rho for the individual level. Effects of time and word length were examined using robust mixed-effects linear regression.

RESULTS

Friedman's tests and correlations indicated no significant difference in WSDs across sampling occasions for each word length separately or combined. WSD correlated positively with AOS severity and negatively with intelligibility but was not correlated with aphasia severity. Regression analyses confirmed WSD to be stable over time, while WSD calculated from only five tokens (i.e., WSD-5) was less stable over time.

CONCLUSIONS

Results indicate that WSD can be a stable measure over time, at the individual and group level, providing support for its use in diagnosis and/or as an outcome measure, both clinically and for research. In general, WSD outperformed WSD-5, suggesting that it may be better to calculate WSD from more than five tokens. Stability of WSD in other populations and suitability for differential diagnosis need to be determined. Currently, differentiating disorders by speaking rate, alone, is not recommended.

SUPPLEMENTAL MATERIAL

https://doi.org/10.23641/asha.25438735.

A reconceptualization of sentence production in post-stroke agrammatic aphasia: the synergistic processing bottleneck model

The language production deficit in post-stroke agrammatic aphasia (PSA-G) tends to result from lesions to the left inferior frontal gyrus (LIFG) and is characterized by a triad of symptoms: fragmented sentences, errors in functional morphology, and a dearth of verbs. Despite decades of research, the mechanisms underlying production patterns in PSA-G have been difficult to characterize. Two major impediments to progress may have been the view that it is a purely morphosyntactic disorder and the (sometimes overzealous) application of linguistic theory without interceding psycholinguistic evidence. In this paper, empirical evidence is examined to present an integrated portrait of language production in PSA-G and to evaluate the assumption of a syntax-specific syndrome. In light of extant evidence, it is proposed that agrammatic language production results from a combination of morphosyntactic, phonomotor, and processing capacity limitations that cause a cumulative processing bottleneck at the point of articulatory planning. This proposed Synergistic Processing Bottleneck model of PSA-G presents a testable framework for future research. The paper ends with recommendations for future research on PSA-G.

Diadochokinesis Performance and Its Link to Cognitive Control: Alternating Versus Non-Alternating Diadochokinesis

PURPOSE

In a previous publication, we observed that maximum speech performance in a nonclinical sample of young adult speakers producing alternating diadochokinesis (DDK) sequences (e.g., rapidly repeating "pataka") was associated with cognitive control: Those with better cognitive switching abilities (i.e., switching flexibly between tasks or mental sets) showed higher DDK accuracy. To follow up on these results, we investigated whether this previously observed association is specific to the rapid production of alternating sequences or also holds for non-alternating sequences (e.g., "tatata").

METHOD

For the same sample of 78 young adults as in our previous study, we additionally analyzed their accuracy and rate performance on non-alternating sequences to investigate whether executive control abilities (i.e., indices of speakers' updating, inhibition, and switching abilities) were more strongly associated with production of alternating, as compared with non-alternating, sequences.

RESULTS

Of the three executive control abilities, only switching predicted both DDK accuracy and rate. The association between cognitive switching (and updating ability) and DDK accuracy was only observed for alternating sequences. The DDK rate model included a simple effect of cognitive switching, such that those with better switching ability showed slower diadochokinetic rates across the board. Thus, those with better cognitive ability showed more accurate (alternating) diadochokinetic production and slower maximum rates for both alternating and non-alternating sequences.

CONCLUSION

These combined results suggest that those with better executive control have better control over their maximum speech performance and show that the link between cognitive control and maximum speech performance also holds for non-alternating sequences.

How to cut the pie is no piece of cake: Toward a process-oriented approach to assessment and diagnosis of speech sound disorders

BACKGROUND

'Speech sound disorder' is an umbrella term that encompasses dysarthria, articulation disorders, childhood apraxia of speech and phonological disorders. However, differential diagnosis between these disorders is a persistent challenge in speech pathology, as many diagnostic procedures use symptom clusters instead of identifying an origin of breakdown in the speech and language system.

AIMS

This article reviews typical and disordered speech through the lens of two well-developed models of production-one focused on phonological encoding and one focused on speech motor planning. We illustrate potential breakdown locations within these models that may relate to childhood apraxia of speech and phonological disorders.

MAIN CONTRIBUTION

This paper presents an overview of an approach to conceptualisation of speech sound disorders that is grounded in current models of speech production and emphasises consideration of underlying processes. The paper also sketches a research agenda for the development of valid, reliable and clinically feasible assessment protocols for children with speech sound disorders.

CONCLUSION

The process-oriented approach outlined here is in the early stages of development but holds promise for developing a more detailed and comprehensive understanding of, and assessment protocols for speech sound disorders that go beyond broad diagnostic labels based on error analysis. Directions for future research are discussed.

WHAT THIS PAPER ADDS

What is already known on the subject Speech sound disorders (SSD) are heterogeneous, and there is agreement that some children have a phonological impairment (phonological disorders, PD) whereas others have an impairment of speech motor planning (childhood apraxia of speech, CAS). There is also recognition that speech production involves multiple processes, and several approaches to the assessment and diagnosis of SSD have been proposed. What this paper adds to existing knowledge This paper provides a more detailed conceptualisation of potential impairments in children with SSD that is grounded in current models of speech production and encourages greater consideration of underlying processes. The paper illustrates this approach and provides guidance for further development. One consequence of this perspective is the notion that broad diagnostic category labels (PD, CAS) may each comprise different subtypes or profiles depending on the processes that are affected. What are the potential or actual clinical implications of this work? Although the approach is in the early stages of development and no comprehensive validated set of tasks and measures is available to assess all processes, clinicians may find the conceptualisation of different underlying processes and the notion of potential subtypes within PD and CAS informative when evaluating SSD. In addition, this perspective discourages either/or thinking (PD or CAS) and instead encourages consideration of the possibility that children may have different combinations of impairments at different processing stages.

Acoustic analysis in stuttering: a machine-learning study

Background

Stuttering is a childhood-onset neurodevelopmental disorder affecting speech fluency. The diagnosis and clinical management of stuttering is currently based on perceptual examination and clinical scales. Standardized techniques for acoustic analysis have prompted promising results for the objective assessment of dysfluency in people with stuttering (PWS).

Objective

We assessed objectively and automatically voice in stuttering, through artificial intelligence (i.e., the support vector machine - SVM classifier). We also investigated the age-related changes affecting voice in stutterers, and verified the relevance of specific speech tasks for the objective and automatic assessment of stuttering.

Methods

Fifty-three PWS (20 children, 33 younger adults) and 71 age-/gender-matched controls (31 children, 40 younger adults) were recruited. Clinical data were assessed through clinical scales. The voluntary and sustained emission of a vowel and two sentences were recorded through smartphones. Audio samples were analyzed using a dedicated machine-learning algorithm, the SVM to compare PWS and controls, both children and younger adults. The receiver operating characteristic (ROC) curves were calculated for a description of the accuracy, for all comparisons. The likelihood ratio (LR), was calculated for each PWS during all speech tasks, for clinical-instrumental correlations, by using an artificial neural network (ANN).

Results

Acoustic analysis based on machine-learning algorithm objectively and automatically discriminated between the overall cohort of PWS and controls with high accuracy (88%). Also, physiologic ageing crucially influenced stuttering as demonstrated by the high accuracy (92%) of machine-learning analysis when classifying children and younger adults PWS. The diagnostic accuracies achieved by machine-learning analysis were comparable for each speech task. The significant clinical-instrumental correlations between LRs and clinical scales supported the biological plausibility of our findings.

Conclusion

Acoustic analysis based on artificial intelligence (SVM) represents a reliable tool for the objective and automatic recognition of stuttering and its relationship with physiologic ageing. The accuracy of the automatic classification is high and independent of the speech task. Machine-learning analysis would help clinicians in the objective diagnosis and clinical management of stuttering. The digital collection of audio samples here achieved through smartphones would promote the future application of the technique in a telemedicine context (home environment).

Do People With Apraxia of Speech and Aphasia Improve or Worsen Across Repeated Sequential Word Trials?

PURPOSE

During motor speech examinations for suspected apraxia of speech (AOS), clients are routinely asked to repeat words several times sequentially. The purpose of this study was to understand the task in terms of the relationship among consecutive attempts. We asked to what extent phonemic accuracy changes across trials and whether the change is predicted by AOS diagnosis and sound production severity.

METHOD

One hundred thirty-three participants were assigned to four diagnostic groups based on quantitative metrics (aphasia plus AOS, aphasia-only, and aphasia with two borderline speech profiles). Each participant produced four multisyllabic words 5 times consecutively. These productions were audio-recorded and transcribed phonetically and then summarized as the proportion of target phonemes that was produced accurately. Nonparametric statistics were used to analyze percent change in accuracy from the first to the last production based on diagnostic group and a broad measure of speech sound accuracy.

RESULTS

Accuracy on the repeated words deteriorated across trials for all groups, showing reduced accuracy from the first to the last repetition for 62% of participants. Although diagnostic groups differed on the broad measure of speech sound accuracy, severity classification based on this measure did not determine degree of deterioration on the repeated words task.

DISCUSSION

Responding to a request to say multisyllabic words 5 times sequentially is challenging for people with aphasia with and without AOS, and as such, performance is prone to errors even with mild impairment. For most, the task does not encourage self-correction. Instead, it promotes errors, regardless of diagnosis, and is, therefore, useful for screening purposes.

Psycholinguistic effects, types of impairments and processing levels in word production: Can we reduce confusions?

This commentary highlights three common difficulties faced by the literature that aims to specify models of speech production based on the performance of aphasic speakers, taking as a springboard a recent study by Mailend et al. These include: (1) difficulties with theoretical assumptions which linki psycholinguistic effects unequivocally to one processing level; (2) difficulties using clinical classifications to localize experimental effects; (3) difficulties making theoretical inferences given the controversial nature of the representations that characterize different processing levels. We argue that these three types of difficulties could be ameliorated by studies in which: (1) the level of psycholinguistic effects is demonstrated with converging analyses; (2) clinical classification is not taken as a starting point in studies investigating the nature of an impairment, but, instead, associations between clusters of symptoms are carefully analysed; (3) The nature of processing levels associated with deficits is made clear and results are not over-interpreted as supporting models whose characteristics go beyond an explanation of the results.

Apraxia of speech and the study of speech production impairments: Can we avoid further confusion? Reply to Romani (2021)

We agree with Cristina Romani (CR) about reducing confusion and agree that the issues raised in her commentary are central to the study of apraxia of speech (AOS). However, CR critiques our approach from the perspective of basic cognitive neuropsychology. This is confusing and misleading because, contrary to CR's claim, we did not attempt to inform models of typical speech production. Instead, we relied on such models to study the impairment in the clinical category of AOS (translational cognitive neuropsychology). Thus, the approach along with the underlying assumptions is different. This response aims to clarify these assumptions, broaden the discussion regarding the methodological approach, and address CR's concerns. We argue that our approach is well-suited to meet the goals of our recent studies and is commensurate with the current state of the science of AOS. Ultimately, a plurality of approaches is needed to understand a phenomenon as complex as AOS.

To Lump or to Split? Possible Subtypes of Apraxia of Speech

BACKGROUND

The speculation that apraxia of speech (AOS) is not a unitary diagnosis, but consists of different subtypes instead, has been around for decades. However, attempts to empirically substantiate such a notion remain few and far between.

AIMS

The primary objective of this article is to consider the different bases for identifying subtypes of AOS, review existing evidence regarding subtypes under each classification basis, and provide discussion and implications for future research.

MAIN CONTRIBUTION

AOS subtypes have been proposed on the basis of clinical symptomatology, theoretical constructs, and an analogy to limb apraxia. Different possible subtypes of AOS are reviewed, along with their empirical support and limitations. Empirical evidence, particularly in the context of a progressive disease, supports the idea that AOS diagnosis may capture different underlying impairments of speech motor planning. Future research to advance our understanding of AOS should carefully consider the basis for subtype classification, and include large sample sizes to differentiate individual variability from possible subtypes.

CONCLUSIONS

Several proposed AOS subtypes have found some support in the literature. Further research is needed to determine the validity, coherence and utility of possible AOS subtypes for theoretical and clinical purposes.