Segmental and prosodic variability on repeated polysyllabic word production in acquired apraxia of speech plus aphasia

Background: McNeil and colleagues argued that individuals with pure apraxia of speech (AOS) have low variability of speech error type and error location within repeated multisyllabic words, compared to individuals with conduction aphasia. While this concept has been challenged, subsequent studies have varied in the stimuli and tasks used.

Aims: Our aim was to re-examine the variability of segmental errors, as well as lexical prosodic errors, using the same stimuli and tasks as used by McNeil and colleagues in a sample of individuals with AOS plus aphasia or aphasia alone. This sample is considered to be clinically relevant given the high concomitance of these disorders.

Methods & Procedures: Participants were 20 individuals with stroke-related AOS plus aphasia and 21 with aphasia alone (APH), with diagnosis based on expert judgments using published criteria. Three consecutive repetitions of 10 polysyllabic words were elicited and variability of error type, error location, and durational stress contrast was measured.

Outcome & Results: Errors were significantly more variable in type and more consistent in location within word for the AOS group than the APH group. The AOS group showed a greater number of errors overall, were less likely to improve production over the three repetition trials, and produced no clear difference in vowel duration across the first two syllables (i.e., durational stress contrast) across repetitions. The measure of durational stress contrast was a stronger predictor of AOS presence than the measures of error variability.

Conclusions: The divergence of our findings from previous work likely reflects the more complex profile of the AOS plus aphasia cases in the current study. While durational stress contrast was sufficient to predict diagnostic group, error variability measures were significantly associated with AOS and can contribute to developing targeted intervention goals.     

An EMA analysis of the effect of increasing word length on consonant production in apraxia of speech: A case study

The effect of increasing word length on the articulatory dynamics (i.e. duration, distance, maximum acceleration, maximum deceleration, and maximum velocity) of consonant production in acquired apraxia of speech was investigated using electromagnetic articulography (EMA). Tongue‐tip and tongue‐back movement of one apraxic patient was recorded using the AG‐200 EMA system during word‐initial consonant productions in one, two, and three syllable words. Significantly deviant articulatory parameters were recorded for each of the target consonants during one, two, and three syllables words. Word length effects were most evident during the release phase of target consonant productions. The results are discussed with respect to theories of speech motor control as they relate to AOS.     

Phonological encoding in apraxia of speech and aphasia

Background: Apraxia of speech (AOS) is considered a speech motor planning/programming disorder. While it is possible that co-occurring phonological impairments exist, the speech motor planning/programming deficit often makes it difficult to assess the phonological encoding stage directly. Studies using online methods have suggested that activation of phonological information may be protracted in AOS.

Aims: The present study was designed to investigate the integrity of the phonological encoding stage in AOS and aphasia. We tested two specific hypotheses, the Frame Hypothesis and the Segment Hypothesis. According to the Frame Hypothesis, speakers with AOS have an impairment in retrieving metrical frames (e.g., number of syllables); according to the Segment Hypothesis, speakers with AOS have an impairment in retrieving segments (e.g., consonants).

Methods & Procedures: Four individuals with AOS and varying degrees of aphasia, two speakers with aphasia, and 13 age-matched control speakers completed an online priming task in which participants name pictures in sets that do or do not share number of syllables (e.g., balcony-coconut-signature vs. balcony-carrot-sock), the initial consonant (e.g., carpenter-castle-cage vs. carpenter-beaver-sun), or both (e.g., boomerang-butterfly-bicycle vs. boomerang-sausage-cat). Error rates and reaction times were measured.

Outcomes & Results: Data for controls replicated previous literature. Reaction time data supported the Segment Hypothesis for speakers with AOS and for one speaker with aphasia without AOS, with no differences in pattern from controls for the other speaker with aphasia without AOS.

Conclusions: These results suggest that speakers with AOS may also have difficulties at the phonological encoding stage. Theoretical and clinical implications of these findings are discussed.     

A speech motor learning approach to treating apraxia of speech: Rationale and effects of intervention with an adult with acquired apraxia of speech

Background: In this paper the rationale for a treatment of apraxia of speech, the speech motor learning (SML) approach, is described and the effects of its application explored. The SML approach endeavours to address the underlying inability to plan and program the production of different speech motor targets (SMTs) in changing phonetic contexts and in utterances exceeding a single word/nonword in length.

Aims: The aims of the study were to determine (1) if treatment effects generalised to untreated nonwords and untreated real words with trained vowels and consonants, (2) if a learning effect was maintained, (3) if the treatment task hierarchy of the SML approach could be confirmed, and (4) if the number of speech errors judged perceptually declined across the treatment period on treated and untreated stages.

Methods & Procedures: A multiple baseline single-participant design across behaviours and contexts was used to assess the effects of treatment with a speaker with chronic pure AOS. The first six stages of an eleven-stage treatment hierarchy were consecutively treated. The last five remained untreated.

Outcomes & Results: During treatment, production of untrained nonwords and words containing trained and untrained SMTs improved. For three treated stages the improvement was greater during the treatment phase than during baseline, for words, nonwords, or both. Stage 4 vowels only improved once treatment commenced. Untreated consonant clusters of Stage 10 improved negligibly. Improvement was maintained 2 years post-treatment. The number of speech errors decreased across the treatment period.

Conclusions: Preliminary evidence is provided supporting a general improvement in speech motor planning and programming ability for this participant. The relative value of components of the SML approach needs to be verified in future.     

An acoustic measure of lexical stress differentiates aphasia and aphasia plus apraxia of speech after stroke

Background: Apraxia of Speech (AOS) is partly characterised by impaired production of prosody in words and sentences. Identification of dysprosody is based on perceptual judgements of clinicians, with limited literature on potential quantitative objective measures.

Aims: This study investigated whether an acoustic measure quantifying degree of lexical stress contrastiveness in three syllable words, produced in isolation and in a carrier sentence, differentiated individuals with AOS with/without aphasia (AOS), aphasia only (APH), and healthy controls (CTL).

Methods & Procedures: Eight individuals with aphasia, nine with AOS plus aphasia and 8 age-matched control participants named pictures of strong–weak and weak–strong polysyllabic words in isolation and in a declarative carrier sentence. Pairwise Variability Indices (PVI) were used to measure the normalised relative vowel duration and peak intensity over the first two syllables of the polysyllabic words.

Outcomes & Results: Individuals with aphasia performed similarly to control participants in all conditions. AOS participants demonstrated significantly lower PVI_vowel duration values for words with weak–strong stress produced in the sentence condition only, compared to controls and individuals with aphasia. This was primarily due to disproportionately long vowels in the word-initial weak syllable for AOS participants. There was no difference among groups on PVI_intensity.

Conclusions: The finding of reduced lexical stress contrastiveness for weak–strong words in sentences for individuals with mild to moderate–severe AOS is consistent with the perceptual diagnostic feature of equal stress in AOS. Findings provide support for use of the objective PVI_vowel duration measure to help differentiate individuals with AOS (with/without aphasia), from those with aphasia only. Future research is warranted to explore the utility of this acoustic measure, and others, for reliable diagnosis of AOS.     

Temporal control in the voicing contrast: Evidence from surgery-related apraxia of speech

ABSTRACT

The goal of this study was to investigate the phonetic realisation of the voicing feature in two tumour resection-related Spanish speakers with apraxia of speech. Temporal parameters related to the phonological contrast of voicing in Spanish have been analysed for intervocalic voiced and voiceless obstruents embedded in isolated words and nonwords, and compared with data collected from healthy speakers. Results indicate that in devoiced productions, where VOT values fitted the ‘voiceless stops’ category, vowel duration values matched those of voiced stops and suggested the preservation of contextual voicing cues. An attempt at preserving a consonant/vowel duration ratio consistent with aerodynamic predictions for voicing contrast has been observed in apraxic correct production as well as in devoicing errors, but not in the control group, which could be interpreted as a compensatory mechanism.     

A case of crossed aphasia with apraxia of speech

Apraxia of speech (AOS) is a rare, but well-defined motor speech disorder. It is characterized by irregular articulatory errors, attempts of self-correction and persistent prosodic abnormalities. Similar to aphasia, AOS is also localized to the dominant cerebral hemisphere. We report a case of Crossed Aphasia with AOS in a 48-year-old right-handed man due to an ischemic infarct in right cerebral hemisphere.     

Voice onset time in aphasia,apraxia of speech and dysarthria: a review

Voice onset time (VOT) is an objective temporal acoustic parameter defined as the time between the release of the oral constriction for plosive production and the onset of vocal fold vibrations. Many researchers consider VOT to be the most reliable acoustic cue for the distinction between voiced and voiceless stops. Previous studies have explored the physiological and linguistic factors underlying VOT production in normal speakers across several languages. A major clinical goal of acoustic analysis in speech disorder is to establish a correlation between the acoustic abnormalities and the phonetic perturbations. VOT could thus be used as an acoustic parameter that indicates the phonetic contrast between voiced and voiceless stops. This paper includes a critical review of the measurement of VOT, factors of VOT variability and the effect of neurogenic communication disorders on VOT. We review the VOT data from subjects who exhibit aphasia, apraxia of speech and dysarthria. These studies reveal that VOT perturbations in aphasia have been interpreted as phonemic or phonetic errors, while VOT abnormalities in apraxia of speech and dysarthria grossly reflect loss of motor control.     

Audio-visual matching of speech and non-speech oral gestures in patients with aphasia and apraxia of speech

BACKGROUND: Audio-visual speech perception mechanisms provide evidence for a supra-modal nature of phonological representations, and a link of these mechanisms to motor representations of speech has been postulated. This leads to the question if aphasic patients and patients with apraxia of speech are able to exploit the visual signal in speech perception and if implicit knowledge of audio-visual relationships is preserved in these patients. Moreover, it is unknown if the audio-visual processing of mouth movements has a specific organisation in the speech as compared to the non-speech domain. METHODS: A discrimination task with speech and non-speech stimuli was applied in four presentation modes: auditory, visual, bimodal and cross-modal. We investigated 14 healthy persons and 14 patients with aphasia and/or apraxia of speech. RESULTS: Patients made substantially more errors than normal subjects on both the speech and the non-speech stimuli, in all presentation modalities. Normal controls made only few errors on the speech stimuli, regardless of the presentation mode, but had a high between-subject variability in the cross-modal matching of non-speech stimuli. The patients' cross-modal processing of non-speech stimuli was mainly predicted by lower face apraxia scores, while their audio-visual matching of syllables was predicted by word repetition abilities and the presence of apraxia of speech. CONCLUSIONS: (1) Impaired speech perception in aphasia is located at a supra-modal representational level. (2) Audio-visual processing is different for speech and non-speech oral gestures. (3) Audio-visual matching abilities in patients with left-hemisphere lesions depend on their speech and non-speech motor abilities.     

Electrical stimulation over the left inferior frontal gyrus (IFG) determines long-term effects in the recovery of speech apraxia in three chronic aphasics

A number of studies have shown that modulating cortical activity by means of transcranial direct current stimulation (tDCS) affects the performance of both healthy and brain-damaged subjects. In this study, we investigated the potential of tDCS for the recovery of apraxia of speech in 3 patients with stroke-induced aphasia. Over 2 weeks, three aphasic subjects participated in a randomized double-blinded experiment involving intensive language training for their articulatory difficulties in two tDCS conditions. Each subject participated in five consecutive daily sessions of anodic tDCS (20 min, 1 mA) and sham stimulation over the left inferior frontal gyrus (referred to as Broca's area) while they performed a repetition task. By the end of each week, a significant improvement was found in both conditions. However, all three subjects showed greater response accuracy in the anodic than in the sham condition. Moreover, results for transfer of treatment effects, although different across subjects, indicate a generalization of the recovery at the language test. Subjects 2 and 3 showed a significant improvement in oral production tasks, such as word repetition and reading, while Subjects 1 and 2 had an unexpected significant recovery in written naming and word writing under dictation tasks. At three follow-ups (1 week, 1 and 2 months after the end of treatment), response accuracy was still significantly better in the anodic than in sham condition, suggesting a long-term effect on the recovery of their articulatory gestures.     

An electropalatographic investigation of linguopalatal contact in participants with acquired apraxia of speech: A quantitative and qualitative analysis

The current study aimed to provide a comprehensive analysis of linguopalatal contact patterns in participants with acquired apraxia of speech (AOS). Tongue‐to‐palate contacts were recorded for three participants with AOS during consonant singletons and consonant clusters using the Reading Electropalatograph (EPG3) system. Amount and pattern of linguopalatal contact were analysed using qualitative and quantitative analysis methods and the degree of spatial variability was quantified. The results obtained for each of the apraxic speakers were individually compared to those obtained by a control group (n = 5). Misdirected articulatory gestures and distorted spatial configurations for alveolar fricatives were detected in the linguopalatal contact patterns recorded for each of the participants with AOS. Lingual overshoot, right‐side dominant contact, and increased spatial variability were also evidenced by some participants. True omission errors were absent. Overall, the combination of qualitative and quantitative analysis techniques proved valuable in providing a comprehensive analysis of linguopalatal contact in AOS. Results provided support for a motoric account of articulatory and prosodic deficits in AOS.     

A diagnostic marker for childhood apraxia of speech: the coefficient of variation ratio

Terms such as isochrony, syllable segregation, scanning speech and staccato‐like rhythmic quality have been used to characterize the temporal regularity that may be a core feature of apraxia of speech. The present report describes a procedure to quantify temporal regularity in children with suspected apraxia of speech (sAOS). Conversational speech samples from 15 such children, together with samples from 30 3–6‐year‐old children with normal speech acquisition and 30 3–6‐year‐old children with moderate to severe speech delay of unknown origin, were selected from an audio archive. Signal processing routines were developed to identify and measure the duration of speech and pause events in 24 utterances from the speech samples of each of the 75 speakers. A value termed the coefficient of variation expressed the normalized variability in the durations of each participant's speech events and pause events within each utterance. A metric termed the coefficient of variation ratio, derived by dividing the coefficient of variation for pause events by the coefficient of variation for speech events, expressed a speaker's relative temporal variation in the two domains. The 15 children with sAOS had higher coefficient of variation ratios than the 30 children in each of the two comparison groups, indicating that the children with sAOS had proportionally more variation in the duration of pause events and/or less variation in the duration of speech events. Findings are interpreted as supporting the view that a constraint in speech timing is a core feature of the praxis disorder that defines a developmental form of apraxia of speech.     

Speech motor control in fluent and dysfluent speech production of an individual with apraxia of speech and Broca's aphasia

Apraxia of speech (AOS) is typically described as a motor‐speech disorder with clinically well‐defined symptoms, but without a clear understanding of the underlying problems in motor control. A number of studies have compared the speech of subjects with AOS to the fluent speech of controls, but only a few have included speech movement data and if so, this was primarily restricted to the study of single articulators. If AOS reflects a basic neuromotor dysfunction, this should somehow be evident in the production of both dysfluent and perceptually fluent speech. The current study compared motor control strategies for the production of perceptually fluent speech between a young woman with apraxia of speech (AOS) and Broca's aphasia and a group of age‐matched control speakers using concepts and tools from articulation‐based theories. In addition, to examine the potential role of specific movement variables on gestural coordination, a second part of this study involved a comparison of fluent and dysfluent speech samples from the speaker with AOS. Movement data from the lips, jaw and tongue were acquired using the AG‐100 EMMA system during the reiterated production of multisyllabic nonwords. The findings indicated that although in general kinematic parameters of fluent speech were similar in the subject with AOS and Broca's aphasia to those of the age‐matched controls, speech task‐related differences were observed in upper lip movements and lip coordination. The comparison between fluent and dysfluent speech characteristics suggested that fluent speech was achieved through the use of specific motor control strategies, highlighting the potential association between the stability of coordinative patterns and movement range, as described in Coordination Dynamics theory.     

A kinematic investigation of anticipatory lingual movement in acquired apraxia of speech

Background: Apraxia of speech (AOS) is considered a disorder of speech planning or programming. Evidence for this stems from perceptual, acoustic, and electropalatographic investigations of articulation in AOS that revealed a delayed onset of anticipatory vowel gestures. Articulatory prolongation and syllable segregation have been attributed to a disturbance in anticipatory coarticulation.

Aims: The aim of the current study was to investigate anticipatory lingual movement for consonantal gestures in AOS, and its impact on absolute and relative speech timing.

Methods & Procedures: Tongue-tip movement and tongue-to-palate contact patterns were recorded for three speakers with AOS and a concomitant aphasia (age range?=?35–63 years; M?=?50.67 years; SD?=?14.29) and five healthy talkers (age range?=?29–65 years; M?=?52.6 years; SD?=?14.5) during the phrases “a scarlet” and “a sergeant”, using electromagnetic articulography (EMA) (AG-200 system) and electropalatography (EPG) (Reading Electropalatograph system). Anticipatory lingual movement and speech timing were analysed during the final C₁VC/C₂ syllable in each of these phrases, where C represented an alveolar or postalveolar consonant. Specifically, tongue-tip displacement was calculated from the onset of release to the end of release of C₁ to provide an indication of anticipatory lingual movement. With respect to speech timing, absolute (i.e., duration from time of maximum contact for C₁ to time of maximum contact for C₂) and relative (i.e., absolute duration expressed as a function of total syllable duration) durational measures were recorded, as was the stability of each. The results recorded for each of the participants with AOS were individually compared to those obtained by the control group.

Outcomes & Results: The EMA results indicated that two participants with AOS exhibited reduced anticipatory lingual movement (i.e., greater tongue-tip displacement) during repetitions of “sergeant”; however, all speakers produced a comparable tongue-tip displacement to that produced by the control group during the release of /l/ in “scarlet”. The EPG results indicated that absolute duration was significantly prolonged during the final syllables of both stimuli for each of the apraxic speakers. Equivocal results were reported for relative timing and temporal stability.

Conclusions: The results provide some preliminary evidence of reduced anticipatory lingual movement in AOS, and have demonstrated that this can have a significant impact on absolute speech timing. However, measures of relative timing were suggestive of either unimpaired or more extensive coarticulation. Additional research is required to resolve this issue.     

The evolution of parkinsonism in primary progressive apraxia of speech: A 6-year longitudinal study

IntroductionPrimary progressive apraxia of speech (PPAOS) is a neurodegenerative syndrome in which patients present with an isolated motor speech disorder. Some PPAOS patients develop parkinsonism and other features of progressive supranuclear palsy (PSP) and/or corticobasal syndrome (CBS) over time. We aimed to assess the evolution of parkinsonian characteristics in PPAOS patients who had been followed yearly for at least six years.MethodsFrom a large cohort of 46 PPAOS patients, eight were followed yearly for > 6-years in multiple NIH-funded grants. Parkinsonian and other features, including bradykinesia, tremor, rigidity, postural instability, apraxia, ocular motor function and cognition were assessed at each visit, and research criteria applied for PSP and CBS diagnosis. Neurological, speech-language test scores, and [¹⁸F]fluorodeoxyglucose PET (FDG-PET) and MRI midbrain volumes were assessed.ResultsA Parkinson's plus syndrome developed in all eight patients (100%). Bradykinesia was the earliest feature, followed by rigidity and postural instability. Tremor was not a significant feature. Parkinsonism, limb apraxia and ocular motor impairment tended to develop four-to-five years after onset with some patients having slight asymmetric parkinsonism. Six patients (75%) met research criteria for probable PSP, although only one for PSP-Richardson's syndrome; three patients met criteria for possible CBS. Slightly asymmetric, left-sided, hypometabolism was observed on FDG-PET, not matching asymmetry of Parkinsonism. Midbrain hypometabolism was absent-minimal. Three patients had progressive midbrain volumes in the PSP-Richardson's syndrome range.ConclusionsA Parkinson's plus syndrome may inevitably develop in PPAOS supporting PPAOS as an early presentation of a Parkinson's plus disorder.     

Segments and syllables in the treatment of apraxia of speech: An investigation of learning and transfer effects

Background: In the treatment of severe apraxia of speech (AOS), single phonemes are often used as training targets. However, until now it remains unclear if segment production can be learned and if patients show transfer effects when a segment trained in isolation is embedded in syllables and words. Speech motor learning in normal language acquisition is based on syllabic rather than segmental learning mechanisms. The syllable is also assumed to be the basic unit of articulatory programming in normal speech.

Aims: In the present study, we investigated the effectiveness of learning single segments as compared to whole syllables in patients with AOS. Besides immediate learning effects, we were particularly interested in transfer effects on trained targets embedded into larger untrained units and in maintenance effects.

Methods & Procedures: Four patients with severe AOS participated in this study. Target segments and target syllables were trained in two separate phases. To examine learning effects, we presented trained and untrained items in isolation immediately before and after a learning phase. Transfer effects of the segmental learning were examined by presenting syllables which contained the target and control phonemes. The transfer of syllabic learning was assessed on the basis of two-syllabic words containing the target and control syllables.

Main Contributions: In the segmental condition, only one patient showed a significant learning effect. Transfer effects onto untrained syllables containing the trained consonants were missing in all patients. After the syllabic training, three patients produced significantly lower error rates on the trained, but not on the control syllables. In two of them, the improvements were still maintained when the syllables were embedded in two-syllabic words.

Conclusions: The lack of segmental learning effects in three patients may be due to the fact that single consonants are artificial speech units we normally do not produce in isolation. The complete absence of transfer effects suggests that intrasyllabic coarticulation is part of the phonetic plan and cannot be mastered by speech apraxic patients without extra exercise. The observed learning effects after the syllabic learning confirm that syllables constitute more natural speech motor units which are easier to re-acquire than single consonants. Furthermore, the embedding of learned monosyllables into unlearned two-syllabic words requires less extra speech motor planning than the embedding of a trained segment into the coarticulated context of a syllable.