Speech Motor Development Research Articles

Auditory–motor interactions in pediatric motor speech disorders: Neurocomputational modeling of disordered development

Background/PurposeDifferentiating the symptom complex due to phonological-level disorders, speech delay and pediatric motor speech disorders is a controversial issue in the field of pediatric speech and language pathology. The present study investigated the developmental interaction between neurological deficits in auditory and motor processes using computational modeling with the DIVA model. MethodIn a series of computer simulations, we investigated the effect of a motor processing deficit alone (MPD), and the effect of a motor processing deficit in combination with an auditory processing deficit (MPD+APD) on the trajectory and endpoint of speech motor development in the DIVA model. ResultsSimulation results showed that a motor programming deficit predominantly leads to deterioration on the phonological level (phonemic mappings) when auditory self-monitoring is intact, and on the systemic level (systemic mapping) if auditory self-monitoring is impaired. ConclusionsThese findings suggest a close relation between quality of auditory self-monitoring and the involvement of phonological vs. motor processes in children with pediatric motor speech disorders. It is suggested that MPD+APD might be involved in typically apraxic speech output disorders and MPD in pediatric motor speech disorders that also have a phonological component. Possibilities to verify these hypotheses using empirical data collected from human subjects are discussed.Learning outcomes: The reader will be able to: (1) identify the difficulties in studying disordered speech motor development; (2) describe the differences in speech motor characteristics between SSD and subtype CAS; (3) describe the different types of learning that occur in the sensory–motor system during babbling and early speech acquisition; (4) identify the neural control subsystems involved in speech production; (5) describe the potential role of auditory self-monitoring in developmental speech disorders.

Motor speech treatment protocol for developmental motor speech disorders

Objective: This study examines the effect of the Motor Speech Treatment Protocol (MSTP), a multi-sensory hybrid treatment approach on five children (mean: 3;3 years; S.D. 0;1) with severe to profound speech sound disorders with motor speech difficulties.Methods: A multiple probe design, replicated over five participants, was used to evaluate the effects of treatment on improving listeners’ auditory and visual judgements of speech accuracy.Results: All participants demonstrated significant change between baseline and maintenance conditions, with the exception of KM, who may have had underlying psychosocial, regulation and/or attention difficulties. The training- (practiced in treatment) and test-words (not practiced in treatment) both demonstrated positive change in all participants, indicating generalization of target features to untrained words.Conclusion: These results provide preliminary evidence that the MSTP, which integrates multi-sensory information and utilizes hierarchical goal selection, may positively impact speech sound production by improving speech motor control in this population.

Electromagnetic articulographic assessment of articulatory kinematics in children, adolescents, and adults

BackgroundThe current understanding of motor skill development of the tongue is limited due to previous difficulty in acquiring physiological data from structures located in the oral cavity.AimThe aim of this study was to examine developmental changes in tongue and lip movements during speech from mid-childhood to adulthood.MethodsThis study used electromagnetic articulography to examine the movement patterns of the tongue-tip, tongue-body, and lower lip in 48 children, adolescents, and adults (aged 6–38 years). Developmental changes during single closing and opening speech movements were evaluated across the target consonants /t/, /s/, /l/, /k/, and /p/, embedded in sentences.ResultsThe experimental findings revealed a general reduction of movement duration with age. Change in movement distance, speed, acceleration, and deceleration, however, showed less consistency. Productions of /s/ and /l/ continued to undergo some kinematic changes in the developmental periods studied; however, few differences were observed for the lingual and labial stops.DiscussionThese results are presented and discussed with reference to current theories of speech motor development and behavior.ConclusionReduced movement duration may be a major feature of motor speech maturation. The developmental progression of distance, speed, acceleration/deceleration of articulatory movements remains less clear.

Auditory plasticity and sensorimotor learning in speech production

Numerous studies have shown the speech motor system to be highly flexible and responsive to changes in sensory input, revealing a central role for both auditory and somatosensory feedback in the acquisition and maintenance of speech motor control. Consistent with these studies, models of speech production have highlighted the role of accurate, stable sensory representations that serve, in part, as the goals of speech movements. A separate (and considerable) body of work has demonstrated that auditory-sensory representations of speech sounds are not perfectly stable, but rather exhibit rapid adaptation to changing input conditions in both children and adults. The plasticity of auditory representations has important implications for the control of speech production, both in early speech motor development and in the sensory-based maintenance of speech accuracy that characterizes adult speech motor control. In this talk, I will describe a series of studies that explore the link between sensory and motor plasticity in the speech motor system. The studies combine the paradigm of sensorimotor adaptation (altering auditory feedback during speech production) with measures and manipulations of auditory-perceptual representations of speech sounds. The results reveal not only that auditory speech targets are flexible under conditions of altered auditory feedback, but that changes in sensory representations can have a direct impact on speech motor learning and performance.

Prelinguistic communication development in children with childhood apraxia of speech: A retrospective analysis

In a retrospective study of prelinguistic communication development, clinically referred preschool children (n = 9) aged 3–4 years, who as infants had failed a community-based screening program, were evaluated for features of childhood apraxia of speech (CAS). Four children showed no features and either delayed or normal language, five had from three-to-seven CAS features and all exhibited delayed language. These children were matched by age with 21 children with typically-developing (TD) speech and language skills. Case-control comparisons of retrospective data from 9 months of age for two participants with more severe features of CAS at preschool age showed a dissociated pattern with low expressive quotients on the Receptive-Expressive Emergent Language Assessment-Second Edition (REEL–2) and records of infrequent babbling, but normal receptive quotients. However, other profiles were observed. Two children with milder CAS features showed poor receptive and expressive development similar to other clinically referred children with no CAS features, and one child with severe CAS features showed poor receptive but normal expressive developmental milestones at 9 months and records of frequent babbling. Results suggest some but not all children with features of suspected CAS have a selective deficit originating within speech motor development.

Five Reasons Why Nonspeech Oral Motor Exercises (NSOME) Do Not Work

Abstract Nonspeech oral motor exercises (NSOME) are used often by speech-language pathologists to help children improve their speech sound productions. However, the phonology, articulation, and motor speech development and disorders literature does not support their use. This article presents five reasons (four theoretical, one empirical) why NSOME are not an appropriate therapeutic technique for treating children's speech sound production problems.

Physiologic Studies Provide New Perspectives on Early Speech Development

Abstract Although certain speech development milestones are readily observable, the developmental course of speech motor control is largely unknown. However, recent advances in facial motion tracking systems have been used to investigate articulator movements in children and the findings from these studies are being used to further our understanding of the physiologic basis of typical and disordered speech development. Physiologic work has revealed that the emergence of speech is highly dependent on the lack of flexibility in the early oromotor system. It also has been determined that the progression of speech motor development is non-linear, a finding that has motivated researchers to investigate how variables such as oromotor control, cognition, and linguistic factors affect speech development in the form of catalysts and constraints. Physiologic data are also being used to determine if non-speech oromotor behaviors play a role in the development of speech. This improved understanding of the physiology underlying speech, as well as the factors influencing its progression, helps inform our understanding of speech motor control in children with disordered speech and provide a framework for theory-driven therapeutic approaches to treatment.

Auditory-Motor Learning during Speech Production in 9-11-Year-Old Children

BackgroundHearing ability is essential for normal speech development, however the precise mechanisms linking auditory input and the improvement of speaking ability remain poorly understood. Auditory feedback during speech production is believed to play a critical role by providing the nervous system with information about speech outcomes that is used to learn and subsequently fine-tune speech motor output. Surprisingly, few studies have directly investigated such auditory-motor learning in the speech production of typically developing children.Methodology/Principal FindingsIn the present study, we manipulated auditory feedback during speech production in a group of 9–11-year old children, as well as in adults. Following a period of speech practice under conditions of altered auditory feedback, compensatory changes in speech production and perception were examined. Consistent with prior studies, the adults exhibited compensatory changes in both their speech motor output and their perceptual representations of speech sound categories. The children exhibited compensatory changes in the motor domain, with a change in speech output that was similar in magnitude to that of the adults, however the children showed no reliable compensatory effect on their perceptual representations.ConclusionsThe results indicate that 9–11-year-old children, whose speech motor and perceptual abilities are still not fully developed, are nonetheless capable of auditory-feedback-based sensorimotor adaptation, supporting a role for such learning processes in speech motor development. Auditory feedback may play a more limited role, however, in the fine-tuning of children's perceptual representations of speech sound categories.

Stability and composition of functional synergies for speech movements in children with developmental speech disorders

The aim of this study was to investigate the consistency and composition of functional synergies for speech movements in children with developmental speech disorders. Kinematic data were collected on the reiterated productions of syllables spa (/spaː/) and paas (/paːs/) by 10 6- to 9-year-olds with developmental speech disorders (five with speech sound disorder [SSD] and five with subtype childhood apraxia of speech [CAS]) and six normally speaking children using electro-magnetic midsagittal articulography (EMMA). Results showed a higher variability of tongue tip movement trajectories and a larger contribution of the lower lip relative to the jaw in oral closures for the five children with CAS compared to normally developing controls, indicating that functional synergies for speech movements in children with CAS may be both delayed and less stable. Furthermore, the SSD group showed a composition of tongue tip movements that is different from both CAS and controls. These results suggest that the differences in speech motor characteristics between SSD and subtype CAS are qualitative rather than quantitative. At the same time, the results suggest that both SSD and subtype CAS increase movement amplitude as an adaptive strategy to increase articulatory stability. Although in direct comparison no exclusive characteristics were found to differentiate subtype CAS from the group of children with SSD and from normally developing children, these preliminary results are promising for quantifying the role of speech motor processes in childhood speech sound disorders. Learning outcomes: The reader will be able to: (1) describe the development of speech motor control and explain the role of functional synergies/coordinative structures; (2) explain the measurement of the stability and composition of speech movements; (3) identify the difficulties in studying disordered speech motor development; (4) describe the differences in speech motor characteristics between SSD and subtype CAS; (5) describe the potential role of motor control strategies in developmental speech disorders.

Early speech motor development: Cognitive and linguistic considerations

This longitudinal investigation examines developmental changes in orofacial movements occurring during the early stages of communication development. The goals were to identify developmental trends in early speech motor performance and to determine how these trends differ across orofacial behaviors thought to vary in cognitive and linguistic demands (i.e., silent spontaneous movements, babble, and first words). Movements of the lower lip and jaw were recorded using a three-dimensional motion capture system. Twenty-four infants were observed every 3 months, from 9 to 21 months of age. Jaw and lower lip speed, and lower lip range of movement increased with age. Silent spontaneous movements were consistently slower than words, whereas kinematic measures associated with babble did not differ from those associated with words. These findings suggest that speech movements may reflect linguistic and cognitive processing demands and that the continuity hypothesis between babbling and words may also be observed at the kinematic level. Learning outcomes Readers will be able to: (1) describe the potential role of cognition and language in early speech development, (2) describe kinematic changes in the orofacial system from 9 to 21 months of age, and (3) identify the differences in kinematic characteristics for silent spontaneous orofacial movements, babbles and words between 15 to 21 months of age.

Foreign accent syndrome as a developmental motor speech disorder

Introduction Foreign Accent Syndrome (FAS) is a relatively rare motor speech disorder in which the pronunciation of a patient is perceived by listeners of the same language community as distinctly foreign. FAS has been well documented in adult patients with etiologically heterogeneous, though mostly vascular brain lesions affecting the motor speech network of the language dominant hemisphere. In addition, reports exist of adult patients in whom FAS was due to a psychiatric illness. Although FAS has been reported in children, such accounts are rare and have remained largely anecdotal in that there have been no formally documented cases of FAS as a developmental motor speech disorder. Methods and results For the first time, we describe the clinical, cognitive and neurolinguistic findings in two patients who in the absence of a history of psychiatric illness or acquired brain damage already presented with FAS at an early stage of speech and language development. In the first patient “developmental FAS” was associated with a dysharmonic distribution of neurocognitive test results indicating slight underdevelopment of visuo-spatial skills and visual memory. The second patient presented with “developmental FAS” associated with specific language impairment (SLI). Independent support for a diagnosis of FAS in both patients was obtained in an accent attribution experiment in which groups of native speakers of (Belgian) Dutch assessed the type of foreign accent of a sample of the patients’ conversational speech. Both patients were judged as non-native speakers of Dutch by the majority of participants who predominantly identified the accent as French. Conclusion This paper for the first time documents two patients who presented with FAS on a developmental basis. The finding that FAS does not only occur in the context of acquired brain damage or psychogenic illness but also exists as developmental motor speech impairment requires a re-definition of FAS as a clinical syndrome.

Developmental Changes in the Effects of Utterance Length and Complexity on Speech Movement Variability

The authors examined the effects of utterance length and linguistic complexity on speech movement consistency for 210 participants between the ages of 5 and 22 years. Variability and durational analyses were conducted to (a) determine a more complete picture of the developmental course of earlier observations of the effects of linguistic constructs on speech motor variability and (b) describe trends for duration of the same sequence of words in different sentential contexts across development. Lower-lip movement was recorded during the production of "buy Bobby a puppy" spoken in isolation as well as embedded as a phrase in 2 longer, more complex sentences. Compared with young adults, children demonstrated higher variability in producing repeated movement sequences for the target word sequence across all conditions. Also, for all age groups except young adults, increased processing demands resulted in significantly increased movement trajectory variability. Duration analyses suggest that around age 9 years, children begin to use adult-like pre-speech processes to plan the timing of sentence internal phrases, and maturation of these planning processes continues through late adolescence. These results provide further evidence for language-motor interactions and for a protracted course of speech motor development that continues well into adolescence.

Duplication of chromosome band 12q24.11q24.23 results in apparent Noonan syndrome

Noonan syndrome is an autosomal dominant disorder with an estimated incidence of 1 in 1,000 to 1 in 2,500 live births. It is characterized by postnatal-onset short stature, characteristic facial changes, webbed neck, pectus carinatum, or excavatum, congenital heart defects, and bleeding abnormalities. Gain-of-function mutations in the PTPN11, KRAS, SOS1, and RAF1 genes that are components of the RAS/MEPK signaling pathway are identified in about 70-85% of individuals with Noonan syndrome. We report here a case of duplication of chromosome region 12q24.11q24.23 identified by array comparative genomic hybridization (aCGH) that includes the PTPN11 gene in a 3-year-old girl with apparent Noonan syndrome. The patient presented with postnatal-onset failure-to-thrive, developmental delay, microcephaly, velopalatal incompetence, pectus excavatum, coarctation of aorta, atrial and ventricular septal defects, decreased muscle tone, and minor facial anomalies consistent with Noonan syndrome. At 3 years of age her speech, gross and fine motor development were at the level of a 12-18 month old child. This degree of developmental delay was atypical for an individual with Noonan syndrome, raising concerns for a chromosomal abnormality. Array-CGH showed an interstitial duplication of 10 Mb including the PTPN11 gene. Sequencing of PTPN11, KRAS, SOS1 and the coding region of RAF1 did not identify mutations. The increased gene dosage of the PTPN11 gene in the form of duplication is expected to have the same consequence as gain-of-function mutations seen in Noonan syndrome. We propose that at least some of the 15-30% of individuals with Noonan syndrome who do not have a mutation by sequencing may have a gain in copy number of PTPN11 and recommend that comprehensive testing for Noonan syndrome should include analysis for copy number changes of PTPN11.

Physiologic Development of Tongue–Jaw Coordination From Childhood to Adulthood

This investigation aimed to examine the development of tongue-jaw coordination during speech from childhood to adolescence. Electromagnetic articulography was used to track tongue and jaw motion in 48 children and adults (aged 6-38 years) during productions of /t/ and /k/ embedded in sentences. The coordinative organization of the tongue and jaw exhibited changes until the age of 8-11 years and continued to undergo refinement into late adolescence. The tongue-tip and tongue-body were observed to develop unique kinematic relations with the jaw. While tongue-tip movement became increasingly synchronized with jaw movement, tongue-body and jaw retained movement independence but developed a more consistent kinematic relation. The present results support the notion that speech motor development is nonuniform, with a refinement period from mid-childhood to late adolescence.

Speech motor development: Integrating muscles, movements, and linguistic units

A fundamental problem for those interested in human communication is to determine how ideas and the various units of language structure are communicated through speaking. The physiological concepts involved in the control of muscle contraction and movement are theoretically distant from the processing levels and units postulated to exist in language production models. A review of the literature on adult speakers suggests that they engage complex, parallel processes involving many units, including sentence, phrase, syllable, and phoneme levels. Infants must develop multilayered interactions among language and motor systems. This discussion describes recent studies of speech motor performance relative to varying linguistic goals during the childhood, teenage, and young adult years. Studies of the developing interactions between speech motor and language systems reveal both qualitative and quantitative differences between the developing and the mature systems. These studies provide an experimental basis for a more comprehensive theoretical account of how mappings between units of language and units of action are formed and how they function. Learning outcomes: Readers will be able to: (1) understand the theoretical differences between models of speech motor control and models of language processing, as well as the nature of the concepts used in the two different kinds of models, (2) explain the concept of coarticulation and state why this phenomenon has confounded attempts to determine the role of linguistic units, such as syllables and phonemes, in speech production, (3) describe the development of speech motor performance skills and specify quantitative and qualitative differences between speech motor performance in children and adults, and (4) describe experimental methods that allow scientists to study speech and limb motor control, as well as compare units of action used to study non-speech and speech movements.

Short-term plasticity in children's speech motor systems

Speech production is a highly skilled behavior that requires rapid and coordinated movements of the orofacial articulators. Previous studies of speech development have shown that children have more variable articulatory movements compared to adults, and cross-sectional studies have revealed that a gradual transition to more stable movement patterns occurs with age. The focus of the present investigation is on the potential role of short-term changes in speech motor performance related to practice. Thus we developed a paradigm to examine the influences of phonological complexity and practice on children (9 and 10-year-olds) and adults' production of novel nonwords. Using two indices that reflect the degree of trial-to-trial consistency of articulatory movements, we analyzed the first and last five productions of the novel nonwords. Both children and adults accurately produced the novel nonwords; however, children showed a practice effect; their last five trials were more consistently produced than their first five trials. Adults did not show this practice effect. This study provides new evidence that children show short-term changes in their speech coordinative patterns with practice. In addition, the present findings support the contribution of neuromotor noise or background, inherent variability to speech motor development.

Speech Motor Development During Acquisition of the Voicing Contrast

Lip and jaw movements were studied longitudinally in 19-month-old children as they acquired the voicing contrast for /p/ and /b/. A movement tracking system obtained lip and jaw kinematics as participants produced the target utterances /papa/ and /baba/. Laryngeal adjustments were also tracked through acoustically recorded voice onset time (VOT) of the consonants. Across this period of developmental phonological change, the children began to produce VOTs in 2 distinct categories for voiced and voiceless plosives. Specific kinematic differences were observed during oral opening and closing and between spatial and temporal parameters of movement. The development of the voicing contrast was most closely associated with changes in jaw kinematics for oral opening in comparison to that of the lip. Conversely, movements into oral closing were not accompanied by significant increases in jaw, upper lip, or lower lip displacement or velocity, although a decrease in jaw movement variability was found. There was no evidence of phoneme-specific movement differences between /p/ and /b/ in the children or in the adults studied. Spatial coupling between the jaw and upper lip changed significantly across sessions, whereas changes in temporal coupling were not observed. Findings indicate that oral opening and closing have different task requirements and that children modify their articulatory movements to meet the demands of each task. Overall, the findings illustrate how orofacial movements and laryngeal function change in parallel during linguistic development.

Imaging speech production using fMRI

Human speech is a well-learned, sensorimotor, and ecological behavior ideal for the study of neural processes and brain-behavior relations. With the advent of modern neuroimaging techniques such as positron emission tomography (PET) and functional magnetic resonance imaging (fMRI), the potential for investigating neural mechanisms of speech motor control, speech motor disorders, and speech motor development has increased. However, a practical issue has limited the application of fMRI to issues in spoken language production and other related behaviors (singing, swallowing). Producing these behaviors during volume acquisition introduces motion-induced signal changes that confound the activation signals of interest. A number of approaches, ranging from signal processing to using silent or covert speech, have attempted to remove or prevent the effects of motion-induced artefact. However, these approaches are flawed for a variety of reasons. An alternative approach, that has only recently been applied to study single-word production, uses pauses in volume acquisition during the production of natural speech motion. Here we present some representative data illustrating the problems associated with motion artefacts and some qualitative results acquired from subjects producing short sentences and orofacial nonspeech movements in the scanner. Using pauses or silent intervals in volume acquisition and block designs, results from individual subjects result in robust activation without motion-induced signal artefact. This approach is an efficient method for studying the neural basis of spoken language production and the effects of speech and language disorders using fMRI.

Development of functional synergies for speech motor coordination in childhood and adolescence.

Adults produce rapid, interleaved sequences of speech sounds by controlling the relative motions in time and space of the oral articulators. The control and coordination of these effectors appear to be automatic, effortless, and usually error free. If speech production is viewed within the framework of classical motor control theories, we can infer that adults have organized functional synergies (consistent patterns of activation of muscle collectives) that act as stable subunits. In this study, the development of these stable functional synergies is examined. Motion of the upper lip, lower lip, and jaw was recorded during sentence production in 180 children and adults (aged 4-22 years). Two indices of oral motor coordination were computed, which reflect the degree of trial-to-trial consistency in intereffector relationships and thus the stability of the underlying functional synergies. Major findings are: (a) The time course of development for speech motor coordination is protracted, (b) speech motor control processes are not adultlike until after age 14 years for both females and males, (c) boys (until age 5 years) show a slower maturational course of speech motor development, and (d) late childhood (the 7- to 12-year period) is characterized by a plateau in the development of these coordinative synergies for speech production. We posit that multiple factors are likely to contribute to the protracted development of oral motor coordination for speech, including maturation of components of the motor system itself and maturation of the brain subsystems for language processing.

Language disorders in young children: when is speech therapy recommended?

Objective: Analysis of treatment recommendation given by speech therapists. Evaluation of the language abilities in the examined children and re-examination of those abilities after 12 months. Materials and methods: Thirty-four children, aged between 2.0 and 5.3 years, referred to speech therapists by their General Practitioners because of possible language problems were included in a prospective study. The number of children receiving speech therapy and the number of speech therapy sessions received during 1 year, and the therapy effect on three quantitative language measures were compiled. Results: In 97% of the children referred to a speech therapist, speech therapy was recommended. Most of these children showed average to above-average language scores on standardised tests for sentence development (61%) and language comprehension (79%). In addition, for most children spontaneous speech, as screened by the Groningen Diagnostic Speech Norms, was age-adequate (76%). The children's problems consisted of pronunciation difficulties or periods of stammering. After 12 months for 50% of these children speech therapy was still continued which means that the articulation problems still were present. The mean number of speech therapy sessions was 26.7. The language scores on the three language tests remained relatively stable over the 12-month interval. Conclusions: In young children pronunciation difficulties often lead to the recommendation for speech therapy. For a large number of children therapy takes more than a year, indicating that speech therapy cannot influence these problems to a great extent. In addition language scores remained relatively stable. Therefore, language problems and especially articulation problems in young children should be reconsidered regarding maturation and normal variations in speech motor development. A ‘watchful waiting’ approach should be taken more often.