Ontogenetically and Phylogenetically Primitive Jaw Movement Stereotypes - Case Study Example

Mandibular Motor Control During the Early Development of Speech and Non-Speech Behaviors When a baby is pre-verbal, he relies upon certain movements in his mouth. For instance, he moves his jaw, and the assumption is that this jaw movement is a precursor to mandibular motor control for speech. Therefore, these jaw movements rely on the same coordinative mechanisms that are later used for early speech. This is one hypothesis. The other hypothesis is that there are parallel coordinative mechanisms during early alimentary behaviors, speech and babble. This hypothesis states that the coordinative mechanisms that support the precursor behavior are not the same as the mechanisms that support early vocalizations. Steeve and Moore have found that the EMG that measure the organization of a baby’s muscle activity show that the first hypothesis might be incorrect, and the second hypothesis is more supported. Further supporting the second hypothesis, that the development of the coordinative mechanisms that support precursor behavior are not the same as the mechanisms that support early vocalizations is the fact that, in adults and children, mandibular motor control is different for speech and chewing. Babies as young as nine-months-old exhibit similar mandibular control to the task specific patterns seen in adults and older children. Therefore, the theory is that the mandibular infrastructure for chewing, sucking and babble are not the same, and are not precursor to, the mandibular infrastructure that governs other developing behaviors, such as speech. It is therefore the purpose of this paper to discover if a motor stereotypy, such as jaw oscillation, can be a precursor for early babble, or if, like the mandibular control, its formation is parallel and distinct with other mandible behaviors. The study examines whether “ontogenetically and phylogentically primitive jaw movement stereotypes” (Moore, p. 5) would “suggest that jaw muscle activation and movement for early speech and non-speech behaviors are similar and are universally apparent in infants.” (Moore, p. 5). Or, the alternative would be that distinct neural infrastructures are present for speech and non-speech behaviors. (Moore, p. 5). The study concerned one male infant who was observed at 4-6 week intervals from the ages of 8 to 22 months. The study observed the infants first instances of babble, at the age of 8 months. The sessions lasted 40 to 60 minutes, and he was observed while he vocalized and ate spontaneously. The study observed him while he was chewing, and observed the jaw oscillations involved with this and his speech utterances. It also observed if these utterances were not coincident with chewing, included at least two syllables, and was speech-like. (Moore, p. 7). A series of technical tests were conducted on the infant. The study also examined the complexity of language as the child matured. The language utterances were broke into three levels. Level 1 was vowel babble. It had a consonant vowel that was not a true consonant, but a glottal or a glide. (Moore, p. 7). Level 2 had at least one true consonant. Level 3 consisted of at least two true consonants. (Moore, p. 7). Age 1 had few Level 3 utterances, age 2 had few level 1 utterances. The theory was that these stages were “influenced deterministically by the interaction of emergent linguistic and motor capacities.” (Moore, p. 22). Specifically, it was the development of the musculoskeletal system that aid speech production that advanced the infants use of more varied and advanced utterances. This was backed up by finding that the mandibular kinetics was more complex for the more complex utterances in the later age group. (Moore, p. 22). The study concluded that the mandibular control for early babble was the same as the motor stereotypy for chewing and jaw oscillation. Coordination was different for multisyllabic productions and non-speech behaviors. This study supported the second hypothesis – that the jaw oscillation developed distinctly for non-speech behaviors, such as chewing and speech behaviors. That is, there are parallel development changes. (Moore, p. 25). Moreover, it is also important that auditory and linguistic development is important in speech, not so important in chewing and jaw oscillation. (Moore, p. 25). The “intertask differences persisted across age, and developmental changes within each behavior were evident.” (Moore, p. 25). Therefore, the study found that mandibular control was task-dependent. If one were to criticize this study, then the focus should be on the fact that this study consisted of only one child. There is no indication that this child was typical of all children his age, and if he is atypical in any way, then this study would not be valid. Project Bridges Gap in Linguistic Skills This article dealt with disadvantaged children in Cork, Ireland and a pilot program that helped these children with their language delays. Before the pilot program began, 43% of the children had language delays, compared to 10% in advantaged areas. (Roche, p. 1). The program involved speech and language development classes in junior infant classes in two schools in Glen. (Roche, p. 2). The pilot program went through September 2007 to June 2008. Before the students began the program, a speech therapist assessed all the students. It was broken into three phases – the first phase consisted of the speech and language therapist meeting with the childrens teachers for 70 minute a week to teach them the basics of a program to help the students. The second phase, from January to March 2008, consisted of the speech and language therapist continuing to support the teachers, but did not meet with them for specified meetings. In the third phase, from April to June 2008, the speech and language therapists met with the children one-on-one. The pilot program was a success, as the kids made significant gains in the speech and language. They also had delays diagnosed at an earlier age, and were able to take advantage of the speech and language therapists if they needed to. Speech Perception and Language Acquisition in the First Year of Life This study was based on the hypothesis that auditory issues in young children, aged 4-5, coincides with speech and language delays. The specific objective of this research was to test how well the children in the study were able to discriminate auditory tones. It was theorized that the children who were least able to discriminate auditory tones would have the most difficulty in completing syllable tasks. The second objective was to determine if the children who had auditory processing deficits also had variance for receptive and expressive language scores. (Bavin, et al., p. 4). The participants of the study were 49 children aged 51 to 67 months. The childrens overall hearing was tested. The other tests consisted of tone; syllable; the Clinical Evaluation of Language Fundamentals-Preschool, which obtained an expressive, and receptive language score, and a second auditory processing task. (Bavin, et al., p. 7). The first prediction made was that “performance on the syllable tasks would be associated with performance on the tone tasks,” and this was supported. (Bavin, et al., p. 8). Children who had difficulty discriminating tones also had difficulty discriminating speech sounds. Another prediction that was supported was that the children would have a “concurrent relationship between auditory processing thresholds and language scores.” (Bavin, et al., p. 9). This study showed that the children who could distinguish frequency at a high level also had better expressive language. This study was supported by the observance that frequency discrimination skills are necessary to identify phoneme and the “patterns of occurrence of these phonemes.” (Bavin, et al., p. 9). Poor frequency discrimination skills are a risk factor for language delays, so this result was not surprising to the researchers. The study also showed that the children with better receptive language scores also performed better on both tone tasks and the SS-FOF task, which was a syllable task. This showed that both frequency discrimination and temporal information are important in language development. It is important for children to “be able to distinguish changes in the dynamic language input in order to map meaning to form and so develop a language system.” (Bavin, et al., p. 9). Overall, the study discovered that children who had high auditory processing thresholds were more at risk for language delays. Auditory perception skills affected both receptive and expressive language. Frequency discrimination affected expressive language. The temporal aspect and frequency for tone and syllable affected the receptive language skills. The authors concluded that more research must be done. In the future, they plan to study impaired children with non-impaired children to determine how different their auditory processing is. This points out a weakness in this study, in that the authors did not compare two distinct groups. They just chose children through the use of advertisements in the Melbourne, Australia area, and they excluded children with existing auditory problems. (Bavin, et al., p. 5). It would have been perhaps more useful to include the children with the existing auditory problems, as this would help in comparing the children with normal auditory perception to children with impaired auditory processing. Read More