Adam Jacks

Token‐to‐token variability in developmental apraxia of speech: three longitudinal case studies

Variability in the speech production patterns of children with developmental apraxia of speech (DAS) was investigated in a three‐year longitudinal study of three children with DAS. A metric was developed to measure token‐to‐token variability in repeated word productions from connected speech samples. Results suggest that high levels of total token and error token variability and low levels of word target stability and token accuracy characterize the disorder. Overall levels of variability and patterns of change over time differed between participants. Longitudinal patterns were indicative of decreasing total token variability and increasing token accuracy. However, change was not consistently unidirectional for two of the three children in the study, suggesting day‐to‐day performance differences in addition to within‐session variability.

Visuomotor Tracking Abilities of Speakers With Apraxia of Speech or Conduction Aphasia

This investigation examined the visuomotor tracking abilities of persons with apraxia of speech (AOS) or conduction aphasia (CA). In addition, tracking performance was correlated with perceptual judgments of speech accuracy. Five individuals with AOS and four with CA served as participants, as well as an equal number of healthy controls matched by age and gender. Participants tracked predictable (sinusoidal) and unpredictable signals using jaw and lip movements transduced with strain gauges. Tracking performance in participants with AOS was poorest for predictable signals, with decreased kinematic measures of cross-correlation and gain ratio and increased target-tracker difference. In contrast, tracking of the unpredictable signal by participants with AOS was performed as well as for other groups (e.g. participants with CA, healthy controls). Performance of the subjects with AOS on the predictable tracking task was found to strongly correlate with perceptual judgments of speech. These findings suggest that motor control capabilities are impaired in AOS, but not in CA. Results suggest that AOS has its basis in motor programming deficits, not impaired motor execution.

Vowel patterns in developmental apraxia of speech: three longitudinal case studies

Vowel inventories and error patterns for three children with suspected developmental apraxia of speech (DAS) were analysed over a 3‐year period using phonetic transcriptions of connected speech samples. The children demonstrated complete English vowel inventories except for rhotics. However, accuracy of vowel targets in connected speech did not normalize during this period. No consistent patterns of vowel errors were found. There was no decrease in vowel accuracy with increased utterance length or syllable complexity. Findings indicate persistence of vowel inaccuracy in the presence of a relatively complete vowel inventory. This longitudinal data can help to build consensus on use of vowels as a potential clinical marker for differential diagnosis of DAS.

Computer-Mediated Assessment of Intelligibility in Aphasia and Apraxia of Speech.

Background: Previous work indicates that single-word intelligibility tests developed for dysarthria are sensitive to segmental production errors in aphasic individuals with and without apraxia of speech. However, potential listener learning effects and difficulties in adapting elicitation procedures to coexisting language impairments limit their applicability to left hemisphere stroke survivors. Aims: The main purpose of this study was to examine basic psychometric properties for a new monosyllabic intelligibility test developed for individuals with aphasia and/or AOS. A related purpose was to examine clinical feasibility and potential to standardise a computer-mediated administration approach. Methods & Procedures: A 600-item monosyllabic single-word intelligibility test was constructed by assembling sets of phonetically similar words. Custom software was used to select 50 target words from this test in a pseudo-random fashion, and to elicit and record production of these words by 23 speakers with aphasia and 20 neurologically healthy participants. To evaluate test–retest reliability, two identical sets of 50-word lists were elicited by requesting repetition after a live speaker model. To examine the effect of a different word set and auditory model, an additional set of 50 different words was elicited with a pre-recorded model. The recorded words were presented to normal-hearing listeners for identification via orthographic and multiple-choice response formats. To examine construct validity, production accuracy for each speaker was estimated via phonetic transcription and rating of overall articulation. Outcomes & Results: Recording and listening tasks were completed in less than 6 minutes for all speakers and listeners. Aphasic speakers were significantly less intelligible than neurologically healthy speakers and displayed a wide range of intelligibility scores. Test–retest and inter-listener reliability estimates were strong. No significant difference was found in scores based on recordings from a live model versus a pre-recorded model, but some individual speakers favoured the live model. Intelligibility test scores correlated highly with segmental accuracy derived from broad phonetic transcription of the same speech sample and a motor speech evaluation. Scores correlated moderately with rated articulation difficulty. Conclusions: We describe a computerised, single-word intelligibility test that yields clinically feasible, reliable, and valid measures of segmental speech production in adults with aphasia. This tool can be used in clinical research to facilitate appropriate participant selection and to establish matching across comparison groups. For a majority of speakers, elicitation procedures can be standardised by using a pre-recorded auditory model for repetition. This assessment tool has potential utility for both clinical assessment and outcomes research.

Speech sound distortions in aphasia and apraxia of speech: reliability and diagnostic significance

Background: The differential diagnosis between apraxia of speech (AOS) and aphasia with phonemic paraphasia is challenging because the disorders share similar speech characteristics. Quantification of the speech profile of AOS is needed. Aims: To characterise the relative frequency of sound distortion errors in speakers with aphasia with and without AOS and to evaluate inter-observer reliability for this metric among independent listeners. Methods & Procedures: Fourteen adults with left hemisphere lesions were recruited from a consecutive clinical sample. They were assigned to groups of probable apraxia of speech (P-AOS) or probable aphasia with phonemic paraphasia (P-APP), based on the multisyllabic word production rate and perceptually evident sound errors. Four listeners generated independent phonetic transcriptions from an audio-recorded motor speech evaluation. The percentage of distorted segments and inter-observer reliability were calculated. Outcomes & Results: Inter-observer reliability was satisfactory for frequency of the overall distortion errors (ICC = 0.73, p < .001). Distortion frequencies were greater in the P-AOS group than in the P-APP group, but varied along on a continuum. Severity effects could not be ruled out, as the overall sound error frequencies were higher in the P-AOS group. Conclusions: With narrow phonetic transcription, independent clinicians can expect to code relative distortion frequency reliably, even though they may differ in the type of distortions they favour and in the absolute rates they observe. Distortion errors are present in speech produced by speakers with aphasia whose speech is characterised by sound error production, and rates are generally higher in stroke survivors who meet prosodic criteria for AOS. The relationship between phonemically salient sound errors and sound distortion frequency should be addressed in future research.

Auditory Masking Effects on Speech Fluency in Apraxia of Speech and Aphasia: Comparison to Altered Auditory Feedback

PURPOSE To study the effects of masked auditory feedback (MAF) on speech fluency in adults with aphasia and/or apraxia of speech (APH/AOS). We hypothesized that adults with AOS would increase speech fluency when speaking with noise. Altered auditory feedback (AAF; i.e., delayed/frequency-shifted feedback) was included as a control condition not expected to improve speech fluency. METHOD Ten participants with APH/AOS and 10 neurologically healthy (NH) participants were studied under both feedback conditions. To allow examination of individual responses, we used an ABACA design. Effects were examined on syllable rate, disfluency duration, and vocal intensity. RESULTS Seven of 10 APH/AOS participants increased fluency with masking by increasing rate, decreasing disfluency duration, or both. In contrast, none of the NH participants increased speaking rate with MAF. In the AAF condition, only 1 APH/AOS participant increased fluency. Four APH/AOS participants and 8 NH participants slowed their rate with AAF. CONCLUSIONS Speaking with MAF appears to increase fluency in a subset of individuals with APH/AOS, indicating that overreliance on auditory feedback monitoring may contribute to their disorder presentation. The distinction between responders and nonresponders was not linked to AOS diagnosis, so additional work is needed to develop hypotheses for candidacy and underlying control mechanisms.

Listener perceptions of simulated fluent speech in nonfluent aphasia

Background: People with aphasia (PWA) are frequently perceived less favourably by listeners than their peers. These perceptions include incorrect assumptions that can prevent successful social interactions. While communication partner training has been shown to improve social outcomes related to the listener, changing the verbal output of PWA may also yield more favourable listener perceptions about the speech, speaker, and their own affective response. We investigated the effects of artificially altered fluency (i.e., simulated fluency) on listeners’ subjective impressions. Aims: The purpose of the study was to (1) confirm that listeners perceive PWA less favourably than their neurologically healthy peers and (2) determine the effects of simulated fluency on listener perceptions about PWA. Methods & Procedures: Thirty-eight listeners heard nine narrative monologue language samples from three conditions (i.e., speakers with nonfluent aphasia, simulated fluent samples from the same speakers, and neurologically healthy speakers). Listeners responded to a nine-item questionnaire that probed perceptions about speech output, speaker attributes, and listener feelings. Outcomes & Results: Listeners perceived PWA less favourably than their neurologically healthy peers. Simulated fluency yielded more positive listener perceptions for all questionnaire items except speech intelligibility, which was unchanged by simulated fluency. Conclusions: Simulated fluency improved listener perceptions of PWA significantly, indicating that speech fluency may be a socially valid treatment target in aphasia. Beyond direct training of communication partners, changing the verbal output of aphasic speech can also yield more positive listener perceptions of PWA.

Perceptually salient sound distortions and apraxia of speech: A performance continuum

Purpose We sought to characterize articulatory distortions in apraxia of speech and aphasia with phonemic paraphasia and to evaluate the diagnostic validity of error frequency of distortion and distorted substitution in differentiating between these disorders. Method Study participants were 66 people with speech sound production difficulties after left-hemisphere stroke or trauma. They were divided into 2 groups on the basis of word syllable duration, which served as an external criterion for speaking rate in multisyllabic words and an index of likely speech diagnosis. Narrow phonetic transcriptions were completed for audio-recorded clinical motor speech evaluations, using 29 diacritic marks. Results Partial voicing and altered vowel tongue placement were common in both groups, and changes in consonant manner and place were also observed. The group with longer word syllable duration produced significantly more distortion and distorted-substitution errors than did the group with shorter word syllable duration, but variations were distributed on a performance continuum that overlapped substantially between groups. Conclusions Segment distortions in focal left-hemisphere lesions can be captured with a customized set of diacritic marks. Frequencies of distortions and distorted substitutions are valid diagnostic criteria for apraxia of speech, but further development of quantitative criteria and dynamic performance profiles is necessary for clinical utility.

Recovering With Acquired Apraxia of Speech: The First 2 Years

Purpose This study was intended to document speech recovery for 1 person with acquired apraxia of speech quantitatively and on the basis of her lived experience. Method The second author sustained a traumatic brain injury that resulted in acquired apraxia of speech. Over a 2-year period, she documented her recovery through 22 video-recorded monologues. We analyzed these monologues using a combination of auditory perceptual, acoustic, and qualitative methods. Results Recovery was evident for all quantitative variables examined. For speech sound production, the recovery was most prominent during the first 3 months, but slower improvement was evident for many months. Measures of speaking rate, fluency, and prosody changed more gradually throughout the entire period. A qualitative analysis of topics addressed in the monologues was consistent with the quantitative speech recovery and indicated a subjective dynamic relationship between accuracy and rate, an observation that several factors made speech sound production variable, and a persisting need for cognitive effort while speaking. Conclusions Speech features improved over an extended time, but the recovery trajectories differed, indicating dynamic reorganization of the underlying speech production system. The relationship among speech dimensions should be examined in other cases and in population samples. The combination of quantitative and qualitative analysis methods offers advantages for understanding clinically relevant aspects of recovery.

Single-word intelligibility testing in aphasia: Alternate forms reliability, phonetic complexity and word frequency

Background: We recently constructed a single-word speech intelligibility test intended to quantify magnitude of speech sound impairment in individuals with aphasia. To minimise listener learning and strategising, the test included a large set of possible (alternate) test forms and was constructed with high and diverse phonologic similarity among candidate words. Although the corpus was limited in phonetic complexity to single syllables, and although criteria for minimal word frequency were applied, it is possible that more fine-grained differences in phonetic complexity and/or word frequency may introduce varying levels of difficulty across alternate test forms and that reliability, therefore, may be compromised. Aims: The dual purposes of this study were to evaluate alternate forms reliability for the new intelligibility test and to determine whether word frequency and/or phonetic complexity affected word identification scores. Methods & Procedures: All words in the 600-word test corpus were coded for overall phonetic complexity and for frequency of occurrence in spoken English. Fifty-one versions of the target 50-word test were generated from this corpus by following designated pseudo-random selection procedures. Speech samples were collected from 13 speakers with aphasia, who each repeated three or four of these 50-word sets. Ten normal-hearing listeners were asked to indicate the words they thought the speakers were trying to say. Per cent accuracy was computed for each speaker, test form and target word. Outcomes & Results: The intra-class correlation within speakers was 0.97, indicating that the scores across alternate forms were highly reproducible. Analyses at the word level showed that both phonetic complexity and word frequency affected identification accuracy. The effects were seen in almost all participants whose intelligibility scores were in the impaired range. Conclusions: High frequency of occurrence and low phonetic complexity increase repetition accuracy for individuals with moderate to severe sound production difficulties and aphasia. However, the pseudo-random word selection in the examined word intelligibility test was sufficient to ensure strong alternate forms reliability. Further constraints on the word selection process for this test are not warranted.