This investigation was designed to describe the development of lip and jaw coordination during speech and to evaluate the potential influence of speech motor development on phonologic development. Productions of syllables containing bilabial consonants were observed from speakers in four age groups (i.e., 1-year-olds, 2-year-olds, 6-year-olds, and young adults). A video-based movement tracking system was used to transduce movement of the upper lip, lower lip, and jaw. The coordinative organization of these articulatory gestures was shown to change dramatically during the first several years of life and to continue to undergo refinement past age 6. The present results are consistent with three primary phases in the development of lip and jaw coordination for speech: integration, differentiation, and refinement. Each of these developmental processes entails the existence of distinct coordinative constraints on early articulatory movement. It is suggested that these constraints will have predictable consequences for the sequence of phonologic development.

Vertical displacements of the upper lip, lower lip, and jaw during speech were recorded for groups of 1-, 2-, and 6-year-olds and adults to examine if control over these articulators develops sequentially. All movement traces were amplitudeand time-normalized. The developmental course of upper lip, lower lip, and jaw control was examined by quantifying age-related changes in the similarity of each articulator's movement patterns to those produced by adult subjects and by same-age peers. In addition, differences in token-to-token stability of articulatory movement were assessed among the different age groups. The experimental findings revealed that 1- and 2-year-old children's jaw movements were significantly more adult-like than their upper and lower lip movements, which were more variable. In contrast, upper and lower lip movement patterns became more adult-like with maturation. These findings suggest that the earliest stages of speech motor development are constrained by the nonuniform development of articulatory control, with the jaw preceding the lips. The observed developmental patterns suggest that the properties of the oral motor control system significantly influence the pattern of speech sound acquisition.

Coordination of jaw muscle activity for speech production sometimes has been modeled using nonspeech behaviors. This orientation has been especially true in representations of mandibular movement in which the synergy of jaw muscles for speech production has been suggested to be derived from the central pattern generator (CPG) for chewing. The present investigation compared the coordination of EMG activity in mandibular muscles over a range of speech and nonspeech tasks. Results of a cross-correlational analysis between EMG signals demonstrated that the muscle synergies of the mandibular system depend on task demands. Contrary to some of the models discussed, continuous speech production yielded activation patterns that were clearly not related to coordinative patterns generated by the chewing CPG.

This investigation was designed to quantify the coordinative organization of mandibular muscles in toddlers during speech and nonspeech behaviors. Seven 15-month-olds were observed during spontaneous production of chewing, sucking, babbling, and speech. Comparison of mandibular coordination across these behaviors revealed that, even for children in the earliest stages of true word production, coordination was quite different from that observed for other behaviors. Production of true words was predominantly characterized by relatively stronger coupling among all mandibular muscles compared with earlier-emerging chewing and sucking. Variegated babbling exhibited stronger coupling than reduplicated babbling, as well as chewing and sucking. The finding of coupled activation among mandibular antagonists during speech paralleled earlier comparisons of adult speech and nonspeech behaviors (Moore, Smith, & Ringel, 1988) and did not support the suggestion that speech coordination emerges from earlier appearing oral motor behaviors. Keywordsspeech; development; motor control; mandible; human A persistent question in our understanding of the coordinative framework of speech production is the relationship of speech to other oral motor behaviors (Moore, Smith, & Ringel, 1988;Ostry, Feltham, & Munhall, 1984;Ostry & Munhall, 1994). Although recent investigations have provided strong support for the existence of separate and distinct mechanisms for speech and nonspeech coordination in adults (Moore et al., 1988), empirical physiologic studies of speech development are lacking. This lack of evidence leaves in doubt the essential foundations of speech motor control.Two lines of reasoning can be taken to address the coordinative framework of speech during the early stages of development. The first draws on mechanisms of pattern generation, which have been directly observed in animals (see Grillner, 1981), as well as dynamical systems theory (e.g., Fentress, 1976;Kent & Hodge, 1990;Thelen & Cooke, 1987;Thelen & Fisher, 1983;Thelen, Skala, & Kelso, 1987; Thelen & Urich, 1991). A dynamic pattern perspective might suggest that speech movements emerge gradually through an interaction of context (i.e., external conditions) with intrinsically generated patterns stemming from the rhythmic movements of sucking, chewing, reduplicated babbling, and variegated babbling. NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author ManuscriptAn alternative approach holds that speech develops independent of extant behaviors, emerging as a new and unique motor skill. Support for this position is drawn directly from observations of babbling rhythmicity (see summary by Kent, Mitchell, & Sancier, 1991) and further relies on findings that the coordinative organization of mature speech is distinct from that of any of the postulated precursors (Moore et al., 1988;Ostry & Munhall, 1994). The established orofacial coordination available to children from these behaviors does not appear to be well suited to speech. For example, kinematic and po...

Syllable Repetition Task (SRT)Purpose. Conceptual and methodological confounds occur when non(sense) repetition tasks are administered to speakers who do not have the target speech sounds in their phonetic inventories or who habitually misarticulate targeted speech sounds. We describe a nonword repetition task, the Syllable Repetiton Task (SRT) that eliminates this confound and report findings from three validity studies.Method. Ninety-five preschool children with Speech Delay and 63 with Typical Speech, completed an assessment battery that included the Nonword Repetition Task (NRT: Dollaghan & Campbell, 1998) and the SRT. SRT stimuli include only four of the earliest occurring consonants and one early occurring vowel.Results. Study 1 findings indicated that the SRT eliminated the speech confound in nonword testing with speakers who misarticulate. Study 2 findings indicated that the accuracy of the SRT to identify expressive language impairment was comparable to findings for the NRT. Study 3 findings illustrated the SRT's potential to interrogate speech processing constraints underlying poor nonword repetition accuracy. Results supported both memorial and auditory-perceptual encoding constraints underlying nonword repetition errors in children with speech-language impairment.3 Conclusion. The SRT appears to be a psychometrically stable and substantively informative nonword repetition task for emerging genetic and other research with speakers who misarticulate. 4 Nonword Repetition Tasks in Genetic Studies of Verbal Trait DisordersFindings from the genetics literature continue to support Adams and Gathercole's (2000) conclusion that poor non(sense)word repetition is a key feature of heritable specific language impairment (SLI). Bishop and colleagues (Bishop, 2002a(Bishop, , 2002bBishop, Adams, & Norbury, 2004;Bishop, Bishop, Bright, Delaney, & Tallal, 1999;Bishop, North, & Donlan, 1996), and Kovas et al. (2005) have reported high heritability for nonword repetition in twin samples and cohorts of children with concurrent or histories of speech-language disorders. Shriberg et al. (2005) reported that in comparison to control participants with speech sound disorders, participants with speech sound disorders who were at familial risk for a genetically transmitted subtype of speech disorder had significantly lower nonword repetition task performance.Molecular genetic studies using nonword repetition tasks have reported linkage to regions of interest on chromosomes 16 and 19 for children with language impairment (Monaco and the SLI Consortium [SLIC], 2007;SLI Consortium, 2002. The first genetic entries for speech sound disorder in the Online Mendelian Inheritance in Man database were based, in part, on linkage of nonword repetition task performance to regions of interest on chromosome 3 (Stein et al., 2004) and chromosome 6 (Smith, Pennington, Boada, & see Caylak, 2007, andLewis et al., 2006 for literature reviews).One property that appears to underlie the productivity of nonword repetition tasks in genetic and other...

Developmental changes in the coordinative organization of masticatory muscles were examined longitudinally in four children over 49 experimental sessions spanning the age range of 12-48 mo. Electromyographic (EMG) records were obtained for right and left masseter muscles, right and left temporalis muscles, and the anterior belly of the digastric. Two independent analytic processes were employed, one that relied on identification of onset and offset of muscle activation and a second that used pairwise cross-correlational techniques. The results of these two analyses, which were found to be consistent with each other, demonstrated that the basic chewing pattern of reciprocally activated antagonistic muscle groups is established by 12 mo of age. Nevertheless, chewing efficiency appears to be improved through a variety of changes in the chewing pattern throughout early development. Coupling of activity among the jaw elevator muscles was shown to strengthen with maturation, and the synchrony of onset and offset of these muscles also increased. Coactivation of antagonistic muscles decreased significantly with development. This decrease in antagonistic coactivation and increase in synchrony among jaw elevators, and a parallel decrease in EMG burst duration, were taken as evidence of increased chewing efficiency. No significant differences in the frequency of chewing were found across the ages studied. Additional considerations include the appropriateness of this coordinative infrastructure for other developing oromotor skills, such as speech production. It is suggested that the relatively fixed coordinative framework for chewing exhibited by these children would not be suitable for adaptation to speech movements, which have been shown to rely on a much more variable and adjustable coordinative organization.

Patients who received LVADs were less severely ill before the operation and consequently were more likely to survive after the operation. As the severity of illness increases, patients are more likely to require biventricular support.

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