Motor programming in apraxia of speech

Apraxia of Speech (AOS) is an impairment of motor programming. However, the exact nature of this deficit remains unclear. The present study examined motor programming in AOS in the context of a recent two-stage model [Klapp, S. T. (1995). Motor response programming during simple and choice reaction time: The role of practice. Journal of Experimental Psychology: Human Perception and Performance, 21, 1015–1027; Klapp, S. T. (2003). Reaction time analysis of two types of motor preparation for speech articulation: Action as a sequence of chunks. Journal of Motor Behavior, 35, 135–150] that proposes a preprogramming stage (INT) and a process that assigns serial order to multiple programs in a sequence (SEQ). The main hypothesis was that AOS involves a process-specific deficit in the INT (preprogramming) stage of processing, rather than in the on-line serial ordering (SEQ) and initiation of movement. In addition, we tested the hypothesis that AOS involves a central (i.e., modality-general) motor programming deficit. We used a reaction time paradigm that provides two dependent measures: study time (the amount of time for participants to ready a motor response; INT), and reaction time (time to initiate movement; SEQ). Two experiments were conducted to examine INT and SEQ in AOS: Experiment 1 involved finger movements, Experiment 2 involved speech movements analogous to the finger movements. Results showed longer preprogramming time for patients with AOS but normal sequencing and initiation times, relative to controls. Together, the findings are consistent with the hypothesis of a process-specific, but central (modality-independent) deficit in AOS; alternative explanations are also discussed.     

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.     

Cognitive mechanisms of visuomotor transformation in movement imitation: Examining predictions based on models of apraxia and motor control

When we observe a movement and then reproduce it, how is this visual input transformed into motor output? Studies on stroke patients with apraxia suggest that there may be two distinct routes used for gesture imitation; an indirect route that recruits stored movement memories (motor programs) and a direct route that bypasses them. The present study examined 30 healthy adults ages 18–80 (mean age = 44.0 years, SD = 19.5) to learn how motor programs are recruited or bypassed in movement imitation depending upon task conditions (whether familiar letters or novel shapes are imitated) and perceptual factors (whether shapes or letters are perceived). Subjects were asked to imitate the movements of a model who formed shapes and letters on a sheer mesh screen, and to report whether they perceived the task as a shape or a letter. Movements were recorded using a Vicon motion analysis system, and subsequently analyzed to determine the degree of difference between the demonstrated and produced movements. As predicted, letter perception on the letter tasks resulted in increased temporal error when the demonstrated stroke order conflicted with subjects’ habitual pattern of letter formation. No such interference effects were observed when the letter tasks were perceived as shapes. These findings are discussed in the context of current theories on imitation, and implications for rehabilitation and motor re-learning are presented.     

Slowly progressive pure dysgraphia with late apraxia of speech: a further variant of the focal cerebral degeneration

We report a longitudinal neuropsychological investigation of a patient with slowly progressive pure dysgraphia. Cognitive analysis of writing errors suggested a selective impairment of the graphemic buffer. After about seven years, the patient developed an apraxia of speech. No other linguistic or generalized cognitive impairment occurred subsequently, so that, twelve years after the beginning of the disease, the patient showed complete independence in daily life and still remained professionally active. Functional neuroimaging revealed hypoperfusion confined to left fronto-temporal lobe. This well-recognizable syndrome does not fit any of the cases described previously in the literature. This report therefore, adds another variant to heterogeneous clinical spectrum of focal neurodegenerative disorders, further suggesting the opportunity of their distinction from pathological processes leading to dementia.     

Task-related factors in oral motor control: speech and oral diadochokinesis in dysarthria and apraxia of speech

This study was focused on the potential influence of task-related factors on oral motor performance in patients with speech disorders. Sentence production was compared with a nonspeech oral motor task, i.e., oral diadochokinesis. Perceptual and acoustic measures of speech impairment were used as dependent variables. Between-task comparisons were made for subsamples of a population of 140 patients with different motor speech syndromes, including apraxia of speech and cerebellar dysarthria. In a further analysis subgroups were matched for speaking rate. Overall, dysdiadochokinesis was correlated with the degree of speech impairment, but there was a strong interaction between task type and motor speech syndrome. In particular, cerebellar pathology affected DDK to a relatively greater extent than sentence production, while apraxic pathology spared the ability of repeating syllables at maximum speed.     

Voice onset time characteristics in apraxia of speech

In order to examine the timing control of laryngeal and supralaryngeal articulatory adjustments in apraxia of speech, voice onset time (VOT) data for stop consonants in monosyllables /de/, /te/, /ge/ and /ke/ were obtained from four apraxic subjects and compared with those of fluent aphasic and normal (both young and aged) speakers (Experiment 1). The results indicated that the VOT distribution patterns of the apraxic patients differed markedly from those of the other speakers. A second experiment was conducted to determine whether the VOT distribution patterns of these four apraxic patients and of two normal controls would change with a lapse of time (Experiment 2). The results of the second experiment demonstrated marked changes in the VOT distribution patterns over time in half of the apraxic patients examined, but essentially no change in the normal controls.     

Contrasting speech patterns in apraxia of speech and phonemic paraphasia

This study was designed to determine if perceptual phonological analysis would reveal distinctions between patients with apraxia of speech and patients with phonemic paraphasic speech. Test findings from 10 Broca's aphasics with apraxia of speech were compared to findings from 10 paraphasic speakers (5 conduction and 5 Wernicke's aphasics). Several marked differences were revealed. Predominant locus of errors and relative difficulty of different classes of phonemic segments were significant discriminators. There was a nonsignificant trend for substituted phonemes to be further from target phonetically in the paraphasic patients. In addition, the two groups showed certain consistent differences in the types of errors they produced. Apraxic patients produced many errors of transitionalization, while sequencing errors were more typical of the patients with phonemic paraphasia. The findings are interpreted in relation to a neuropsychological model of speech. It is suggested that phonemic paraphasia represents a breakdown mainly in the retrieval of phonological word patterns, while apraxia of speech is characterized predominantly by a disturbance in encoding phonological patterns into appropriate speech movements.     

Velar movements during speech in a patient with apraxia of speech.

A fiberscopic observation of velar movements during speech was made of a patient diagnosed as having apraxia of speech. Repeated utterances of the same word showed a marked variability in terms of the pattern of velar movements accompanied at times by a phonetic change. In spite of such a variability, the general successional pattern of velar gestures for a given phonetic context approximated the normal pattern. During the production of nasal and nonnasal consonants the velum tended to take “neutral” positions. Anticipatory coarticulation was present, but some deviation from normal patterns was occasionally observed. Based on these observations, possible mechanisms responsible for the syndrome called apraxia of speech were discussed.     

Private and inner speech and the regulation of social speech communication

To further investigate the possible regulatory role of private and inner speech in the context of referential social speech communications, a set of clear and systematically applied measures is needed. This study addresses this need by introducing a rigorous method for identifying private speech and certain sharply defined instances of inaudible inner speech. Using this classification system, longitudinal data were gathered from 10 pairs of children performing a referential communication task at 4.5, 6.5, and 8.5 years of age. Results demonstrated children's substantial production of private and inner speech in this communicative situation, with speech forms varying in amount and type as a function of age, communicative role (speaker or listener), and the complexity of the material to be communicated. It is suggested that private and inner speech embedded in discourse may serve a regulatory role in social speech communication.     

Nonspeech and speech processing skills in patients with aphasia and apraxia of speech

Nonspeech and speech auditory processing skills as well as internal speech processing skills were assessed among four patients with acquired "pure" apraxia of speech, 10 with acquired aphasia, 10 with aphasia plus apraxia of speech, and 11 neurologically normal adults. Fourteen tasks were administered and performances on 68 variables were examined using both nonparametric and parametric analyses controlling for the effects of advancing age and associated hearing loss. In all cases, the "pure" apractic patients performed as normal subjects. Few differences were noted among the performances of the aphasic and aphasic-apractic subjects. Results led to three major conclusions: (1) apraxia of speech is a disorder distinct from aphasia; (2) aphasic individuals, despite locus of lesion, demonstrate disabilities for processing nonspeech and speech materials presented auditorily and for analytically evaluating speech evoked internally; and (3) aphasic individuals demonstrating similar severity levels of language impairment show similar performance patterns for these types of processing tasks, despite locus of lesion or coexistence of apraxia of speech.     

An experimental investigation of the automatic/voluntary dissociation in limb apraxia

The ability of apraxic patients to perform gestures in everyday life is a controversial issue. In this paper, we aimed to evaluate the automatic/voluntary dissociation (AVD) in four patients affected by clinically relevant limb apraxia. For this purpose, we sampled different kinds of gestures belonging to patients' motor repertoire and then assessed their production in a testing session. Our experimental procedure consisted of two steps: in the first phase, we recorded gestures produced by patients in two natural conditions; in the second phase, we assessed production of correctly produced tool-actions, and of spontaneous non tool-actions and meaningless conversational (cohesive and beats) gestures under different modalities. AVD was observed for all types of gestures, albeit to different degree in single patients. The present findings demonstrate that the context provides strong bottom-up cues for the retrieval of motor patterns, while artificial testing conditions impose an additional cognitive load.     

Syllable frequency and syllable structure in apraxia of speech

Recent accounts of the pathomechanism underlying apraxia of speech (AOS) were based on the speech production model of Levelt, Roelofs, and Meyer, and Meyer (1999)1999. The apraxic impairment was localized to the phonetic encoding level where the model postulates a mental store of motor programs for high-frequency syllables. Varley and Whiteside (2001a) assumed that in patients with AOS syllabic motor programs are no longer accessible and that these patients are required to use a subsyllabic encoding route. In this study, we tested this hypothesis by exploring the influence of syllable frequency and syllable structure on word repetition in 10 patients with AOS. A significant effect of syllable frequency on error rates was found. Moreover, apraxic errors on consonant clusters were influenced by their position relative to syllable boundaries. These results demonstrate that apraxic patients have access to the syllabary, but that they fail to retrieve the syllabic motor patterns correctly. Our findings are incompatible with a subsyllabic route model of apraxia of speech.     

Maternal and paternal infant-directed speech to girls and boys: An exploratory study

ABSTRACT

We compared systematically the structure and the content of maternal and paternal speech to infant boys and girls while we also investigated the effect of infant’s age. Six girls and five boys were observed in the interaction with their mothers and their fathers (dyads came from the same families) at home from the second to the sixth month after birth at 15- day intervals. Detailed analysis of time revealed that fathers favour systematically the temporal structure of their speech to both girls and boys, while mothers favour boys in infant emotion/attention thematic sequences and girls in infant attention speech. Variations are counterbalanced in the way mothers and fathers respond sensitively to known marked changes in infant- parent communication over the first 6 months of life. These results are discussing in relation to the theory of innate intersubjectivity and the complementary company and care both parents give to developing infant girls and boys.     

Anticipatory coarticulation in a patient with apraxia of speech

Articulatory anticipation of vowel gestures was assessed in an apraxic patient, a dysarthric patient, and three normal speakers. The technique of assessment included perceptual identification of gated speech stimuli. The speech material consisted of /getVte/ utterances with the target vowels /i/, /y/, and /u/. In the case of the apraxic patient the gated vowels were identified at a later instant relative to the preceding plosion burst than in the normal speakers. This result was interpreted as reflecting a delayed onset of coarticulatory gestures, in particular lip rounding. The identification rates for the dysarthric's vowels rather reflected the general reduction of this patient's vowel space.     

Phonetic recalibration only occurs in speech mode

Upon hearing an ambiguous speech sound dubbed onto lipread speech, listeners adjust their phonetic categories in accordance with the lipread information (recalibration) that tells what the phoneme should be. Here we used sine wave speech (SWS) to show that this tuning effect occurs if the SWS sounds are perceived as speech, but not if the sounds are perceived as non-speech. In contrast, selective speech adaptation occurred irrespective of whether listeners were in speech or non-speech mode. These results provide new evidence for the distinction between a speech and non-speech processing mode, and they demonstrate that different mechanisms underlie recalibration and selective speech adaptation.     

言语想象的神经机制

言语想象不仅在大脑预处理机制方面起到重要的作用,还是目前脑机接口领域研究的热点。与正常言语产生过程相比,言语想象的理论模型、激活脑区、神经传导路径等均与其有较多相似之处。而言语障碍群体的言语想象、想象有意义的词语和句子时的脑神经机制与正常言语产生存在差异。鉴于人类言语系统的复杂性,言语想象的神经机制研究还面临一系列挑战,未来研究可在言语想象质量评价工具及神经解码范式、脑控制回路、激活通路、言语障碍群体的言语想象机制、词语和句子想象的脑神经信号等方面进一步探索,为有效提高脑机接口的识别率提供依据,为言语障碍群体的沟通提供便利。     

Abnormal articulatory dynamics in a patient with apraxia of speech: X-ray microbeam observation

The temporal organization of articulatory movements in a patient diagnosed as having apraxia of speech was explored by means of pellet tracking techniques using an X-ray microbeam system. The results indicated that the temporal organization among different articulators of the patient was sometimes disturbed in his production of a meaningful Japanese word /deenee/. It was also observed that the pattern and velocity of the articulatory movements of the patient in repetitions of monosyllables were different from those of typical dysarthric patients.