Lingual articulation in children with developmental speech disorders

This thesis presents thirteen research papers published between 1987-97, and a summary and discussion of their contribution to the field of developmental speech disorders. The publications collectively constitute a body of work with two overarching themes. The first is methodological: all the publications report articulatory data relating to tongue movements recorded using the instrumental technique of electropalatography (EPG). The second is the clinical orientation of the research: the EPG data are interpreted throughout for the purpose of informing the theory and practice of speech pathology. The majority of the publications are original, experimental studies of lingual articulation in children with developmental speech disorders. At the same time the publications cover a broad range of theoretical and clinical issues relating to lingual articulation including: articulation in normal speakers, the clinical applications of EPG, data analysis procedures, articulation in second language learners, and the effect of oral surgery on articulation. The contribution of the publications to the field of developmental speech disorders of unknown origin, also known as phonological impairment or functional articulation disorder, is summarised and discussed. In total, EPG data from fourteen children are reported. The collective results from the publications do not support the cognitive/linguistic explanation of developmental speech disorders. Instead, the EPG findings are marshalled to build the case that specific deficits in speech motor control can account for many of the diverse speech error characteristics identified by perceptual analysis in previous studies. Some of the children studied had speech motor deficits that were relatively discrete, involving, for example, an apparently isolated difficulty with tongue tiplblade groove formation for sibilant targets. Articulatory difficulties of the 'discrete' or specific type are consistent with traditional views of functional lingual articulation in developmental speech disorders articulation disorder. EPG studies of tongue control in normal adults provided insights into a different type of speech motor control deficit observed in the speech of many of the children studied. Unlike the children with discrete articulatory difficulties, others produced abnormal EPG patterns for a wide range of lingual targets. These abnormal gestures were characterised by broad, undifferentiated tongue-palate contact, accompanied by variable approach and release phases. These 'widespread', undifferentiated gestures are interpreted as constituting a previously undescribed form of speech motor deficit, resulting from a difficulty in controlling the tongue tip/blade system independently of the tongue body. Undifferentiated gestures were found to result in variable percepts depending on the target and the timing of the particular gesture, and may manifest as perceptually acceptable productions, phonological substitutions or phonetic distortions. It is suggested that discrete and widespread speech motor deficits reflect different stages along a developmental or severity continuum, rather than distinct subgroups with different underlying deficits. The children studied all manifested speech motor control deficits of varying degrees along this continuum. It is argued that it is the unique anatomical properties of the tongue, combined with the high level of spatial and temporal accuracy required for tongue tiplblade and tongue body co-ordination, that put lingual control specifically at risk in young children. The EPG findings question the validity of assumptions made about the presence/absence of speech motor control deficits, when such assumptions are based entirely on non-instrumental assessment procedures. A novel account of the sequence of acquisition of alveolar stop articulation in children with normal speech development is proposed, based on the EPG data from the children with developmental speech disorders. It is suggested that broad, undifferentiated gestures may occur in young normal children, and that adult-like lingual control develops gradually through the processes of differentiation and integration. Finally, the EPG fmdings are discussed in relation to two recent theoretical frameworks, that of psycho linguistic models and a dynamic systems approach to speech acquisition

Abnormal patterns of tongue-palate contact in the speech of individuals with cleft palate

Individuals with cleft palate, even those with adequate velopharyngeal function, are at high risk for disordered lingual articulation. This article attempts to summarize current knowledge of abnormal tongue-palate contact patterns derived from electropalatographic (EPG) data in speakers with cleft palate. These data, which have been reported in 23 articles published over the past 20 years, have added significantly to our knowledge about cleft palate speech. Eight abnormal patterns of tongue-palate contact are described and illustrated with data from children and adults with repaired cleft palate. The paper also discusses some of the problems in interpreting EPG data from speakers with abnormal craniofacial anatomy and emphasizes the importance of quantifying relevant aspects of tongue-palate contact data. Areas of research requiring further investigation are outlined

Preschool children's performance on profiling elements of prosody in speech-communication (PEPS-C)

Profiling Elements of Prosody in Speech-Communication (PEPS-C) has not been used widely to assess prosodic abilities of preschool children. This study was therefore aimed at investigating typically developing 4-year-olds' performance on PEPS-C. PEPS-C was presented to 30 typically developing 4-year-olds recruited in southern Ireland. Children were judged to have completed the test if they produced analysable responses to >95% of the items. The children's scores were compared with data from typically developing 5–6-year-olds. The majority (83%) of 4-year-olds were able to complete the test. The children scored at chance or weak ability levels on all subtests. The 4-year-olds had lower scores than 5–6-year-olds in all subtests, apart from one, with the difference reaching statistical significance in 8 out of 12 subtests. The results indicate that PEPS-C could be a valuable tool for assessing prosody in young children with typical development and some groups of young children with communication disorders

Non-speech oral motor treatment for developmental speech sound disorders in children (Protocol)

Objective: To assess the efficacy of non-speech oral motor treatment (NSOMT) for treating developmental speech sound disorders

Using EPG data to display articulatory separation for phoneme contrasts

A recurring difficulty for researchers using electropalatography (EPG) is the wide variation in spatial patterns that occurs between speakers. High inter speaker variability, combined with small numbers of participants, makes it problematic (i) to identify differences in tongue palate contact across groups of speakers and (ii) to define “normal” patterns during visual feedback therapy. This paper shows how graphing EPG data in terms of articulatory separation of phoneme contrasts reduces these two problems to some extent. The graphs emphasise the importance of establishing the presence and extent of separation, as revealed in the EPG data, for phoneme contrasts produced by speakers. Separation graphs for contrasts /i/ - /u/, /s/ - /ʃ/ and /t/ - /k/ are presented using EPG data from adults and children with typical speech and those with speech disorders. When used in conjunction with acoustic and auditory perceptual analyses, it is proposed that representing articulation data in terms of separation will prove useful for a range of clinical and research purposes

Producing turbulent speech sounds in the context of cleft palate

Aims and Scope: No sound class requires so much basic knowledge of phonology, acoustics, aerodynamics, and speech production as obstruents (turbulent sounds) do. This book is intended to bridge a gap by introducing the reader to the world of obstruents from a multidisciplinary perspective. It starts with a review of typological processes, continues with various contributions to the phonetics-phonology interface, explains the realization of specific turbulent sounds in endangered languages, and finishes with surveys of obstruents from a sociophonetic, physical and pathological perspective

Undifferentiated lingual gestures and their implications for speech disorders in children

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Adult speakers' tongue-palate contact patterns for bilabial stops within complex clusters

Previous studies using Electropalatography (EPG) have shown that individuals with speech disorders sometimes produce articulation errors that affect bilabial targets, but currently there is limited normative data available. In this study, EPG and acoustic data were recorded during complex word final /sps/ clusters spoken by 20 normal adults. A total contact (TC) index measured amount of tongue-palate contact during clusters in words such as 'crisps'. Bilabial closure was inferred from the acoustic signal. The TC profiles indicated that normal adults hold their tongues in a steady /s/-like position throughout the cluster; most speakers (85%, n=17) had no significant difference in TC values during bilabial closure compared to flanking fricatives. The results are interpreted as showing that normal speakers produce double bilabial-alveolar articulations for /p/ in these clusters. Although steady state TC profiles were typical of the group, absolute TC values varied considerably between speakers, with some speakers having up to three times more contact than others. These findings add to the knowledge about normal articulation, and will help to improve diagnosis and treatment of individuals with speech disorders