Margaret Denny

Implications of peripheral muscular and anatomical development for the acquisition of lingual control for speech production: a review.

Objectives: Normally developing children learn to produce intelligible speech during rapid, non-uniform growth of their articulators and other vocal tract structures. The purpose of this review is to focus attention on the consequences of peripheral growth and development for the acquisition of lingual control for speech production. This paper (1) reviews physiological underpinnings of tongue shaping and movements that are likely to be changing in young children; (2) estimates, from previously published studies, the net consequences of growth of multiple vocal tract structures on lingual control; (3) integrates our findings with the example of [R] production, and (4) highlights areas where further investigations would be most helpful. Patients and Methods: The authors searched the literature, including the PubMed database, for studies of the development of muscle proteins, muscle fibers, and motor units of the tongue, and of the growth of the tongue, jaw, adenoids, soft and hard palates, oral and pharyngeal cavities, and the vocal tract as a whole. Conclusions: Substantial anatomical and muscular data sets focused on children from 1–4 years of age, and rigorous definitions of the tongue boundaries are needed.

Sagittal Area of the Vocal Tract in Young Female Children

Objective: To measure the sagittal areas of the front and back cavities of the vocal tract in children acquiring speech. Patients and Methods: Ten female children were selected from the Serial Experimental collection of the Burlington Growth Centre in Toronto, Canada. Each of the 10 children was seen annually from ages 3 through 8. Data collections included lateral cephalograms in occlusion. We traced those cephalograms and identified landmarks to delineate the front and back cavities. The sagittal areas of the front and back cavities were calculated. A measure of the angle of the head to the cervical vertebrae was made. Results: Front cavities were larger and grew faster. For both front and back cavities, age, angle measure, and the interaction of age and angle measure were significant. Conclusion: Space available for the tongue to maneuver is greater anteriorly than posteriorly even when the jaw is maximally elevated.

Alveolar and velar stop releases during speech development.

It has been shown that children learning English tend to use tongue‐to‐palate contact patterns while producing velar and alveolar stop consonants that are not as well differentiated as for adults [Cheng et al., J. Speech, Language, Hearing Res. 50, 375–392 (2007)]. The electropalatographic experiments suggest that young children have not developed the fine motor control necessary for mature articulation of lingual consonants. It is possible that this may persist to become a speech disorder as they mature. We offer a complementary perspective that focuses on the mismatch between the acoustic and aerodynamic scaling from children’s vocal tracts to adult vocal tracts. In learning the motor control necessary to make a good distinction between alveolar and velar stops may be hindered by scaling mismatches. In this paper we will highlight acoustic measures of four children recorded every 6 months from the ages of 12–48 months playing with a care giver. We will consider both the formant frequencies at release and the shape of the burst spectrum to both help characterize the development acoustically and to infer what is causing the acoustics in the articulation. [Work supported by Grant No. NIDCD‐RO1‐001247.]

Functional anatomy of the human tongue: Review and implications for the development of speech production.

To acquire speech children must attempt to reproduce adult acoustic models using immature vocal tracts which differ from those of adults in complex ways. Control of the tongue is crucial for acceptable speech, yet the tongue is an understudied articulator because it is anatomically complex and difficult to record from using kinematic or electrophysiological methods. Nevertheless recent advances in tongue anatomy and physiology, combined with knowledge of vocal tract development, promise to shed light on the problems that children must solve in learning to speak as well as the solutions available to them. This review aims to integrate and present these findings to an audience interested in the development of speech production. A striking finding is that the tongue shows an anterior‐to‐posterior gradient in muscle fiber sizes and types. In multiple muscles, faster fibers are more common anteriorly while slower fibers are more predominant in the posterior tongue. Within fiber type (fast or slow) smaller fibe...

Vowel space of 3‐ and 4‐year‐old children.

Children learn to produce speech within the constraints of vocal tracts that are smaller and configured differently from those of adult speakers. To study children’s speech development in relation to their vocal tract growth, the acoustic characteristics of vowels spoken by ten children, recorded at 6 month intervals between the ages of 36 and 48 months and a subset between 18 and 48 months, are analyzed. The first three formant frequencies of each token are measured and tokens are categorized by intended vowel. Formant frequencies are compared both among vowel categories at each age and within categories over time to give an understanding of the development of children’s vowel space. Changes in children’s ability to differentiate among vowels in F1‐F2 space over time are investigated. The development of vowel space is considered in the context of growth of and changes in the proportions of the vocal tract and improved control of the articulators. [Work supported by NIDCD‐0001247 to CReSS LLC.]

Effects of speaking condition and hearing status on vowel production in postlingually deaf adults with cochlear implant

This study investigates the effects of speaking condition and hearing status on vowel production by postlingually deafened adults. Thirteen cochlear implant users produced repetitions of nine American English vowels in three time samples (prior to implantation, one month, and one year after implantation); in three speaking conditions (clear, normal, and fast); and in two feedback conditions after implantation (implant processor turned on and off). Ten speakers with normal hearing were also recorded. Results show that vowel contrast, in the F1 versus F2 space, in mels, does not differ from the pre‐implant stage to the 1‐month stage. This finding indicates that shortly after implantation, speakers had not had enough experience with hearing from the implant to adequately retune their auditory feedback systems and use auditory feedback to improve feedforward commands. After 1 year of implant use, contrast distances had increased in both feedback conditions (processor on and off), indicating improvement in feedforward commands for phoneme production. Furthermore, after long‐term auditory deprivation, speakers were producing differences in contrast between clear and fast conditions in the range of those found for normal‐hearing speakers, leading to the inference that maintenance of these distinctions is not affected by hearing status. [Research supported by NIDCD.]