Measures of performance rates in speech-like or volitional nonspeech oral motor tasks are frequently used to draw inferences about articulation rate abnormalities in patients with neurologic movement disorders. The study objective was to investigate the structural relationship between rate measures of speech and of oral motor behaviors different from speech. A total of 130 patients with neurologic movement disorders and 130 healthy subjects participated in the study. Rate data was collected for oral reading (speech), rapid syllable repetition (speech-like), and rapid single articulator movements (nonspeech). The authors used factor analysis to determine whether the different rate variables reflect the same or distinct constructs. The behavioral data were most appropriately captured by a measurement model in which the different task types loaded onto separate latent variables. The data on oral motor performance rates show that speech tasks and oral motor tasks such as rapid syllable repetition or repetitive single articulator movements measure separate traits.

Nonspeech (or paraspeech) parameters are widely used in clinical assessment of speech impairment in persons with dysarthria (PWD). Virtually every standard clinical instrument used in dysarthria diagnostics includes nonspeech parameters, often in considerable numbers. While theoretical considerations have challenged the validity of these measures as markers of speech impairment, only a few studies have directly examined their relationship to speech parameters on a broader scale. This study was designed to investigate how nonspeech parameters commonly used in clinical dysarthria assessment relate to speech characteristics of dysarthria in individuals with movement disorders. Maximum syllable repetition rates, accuracies, and rates of isolated and repetitive nonspeech oral–facial movements and maximum phonation times were compared with auditory–perceptual and acoustic speech parameters. Overall, 23 diagnostic parameters were assessed in a sample of 130 patients with movement disorders of six etiologies. Each variable was standardized for its distribution and for age and sex effects in 130 neurotypical speakers. Exploratory Graph Analysis (EGA) and Confirmatory Factor Analysis (CFA) were used to examine the factor structure underlying the diagnostic parameters. In the first analysis, we tested the hypothesis that nonspeech parameters combine with speech parameters within diagnostic dimensions representing domain–general motor control principles. In a second analysis, we tested the more specific hypotheses that diagnostic parameters split along effector (lip vs. tongue) or functional (speed vs. accuracy) rather than task boundaries. Our findings contradict the view that nonspeech parameters currently used in dysarthria diagnostics are congruent with diagnostic measures of speech characteristics in PWD.

Background: Apraxia of speech (AOS) is generally viewed as a disorder of phonetic encoding. According to current theories, the phonetic encoding process is considered to be based on linear strings of holistic speech motor representations of the size of sub‐lexical units (e.g., phonemes or syllables). This type of model predicts that error rate in apraxia of speech is proportional to the number of phonetic encoding units in an utterance and is not systematically influenced by structural factors originating above or below the level of the critical unit. Aims: In the present study we tested this prediction for five models based on different units of phonetic encoding. Methods and Procedures: Ten patients with AOS were examined with a list of words of varying phonological complexity. Phoneme errors in word repetition were counted in different ways, according to five models postulating different domains of phonetic encoding. Linear regression analyses were used to examine the scores obtained for these models for influences of structural factors. Outcomes & Results: No sublexical unit could be identified that was not systematically influenced by one of the structural factors describing the materials. Major influencing factors were (1) the complexity of syllable constituents and (2) the number of metrical feet in a word. Conclusions: A model of phonetic encoding in apraxia of speech is proposed that is based on a hierarchy of structural relationships rather than on linearly ordered, holistic programming units. This model may also contain clues for a theory of normal processing mechanisms.

This paper presents new treatment approaches for patients with apraxia of speech (AOS), which are based on current theoretical work relating to the pathomechanism of AOS. Particularly, we focus on the question of which speech units and structural properties are involved in the error mechanism of speakers with apraxia. Based on a psycholinguistic model of spoken language production (Levelt, Roelofs, & Meyer, 1999), we review data from single-word production experiments and from analyses of spontaneous speech demonstrating an impact on (a) the degree of “over-learnedness” of syllables (syllable frequency), (b) the internal structure of syllables (syllable complexity), and (c) supra-syllabic, metrical aspects of utterances (word stress) on error production in AOS. In the second section, we present two experimental learning studies and a treatment study that take these results into consideration. The first learning experiment suggests that syllables are more natural units than segments in the treatment of patients with severe AOS. Based on the results of the second learning study, we recommend a treatment approach which uses formally related training syllables in the reacquisition of complex target syllables. Finally, results of a treatment study using a metrical pacing technique led to the assumption that fluency and segmental accuracy could be enhanced by external rhythmic cues.