Speech Perception and Motor Control in Children with Down Syndrome

Abstract

Twelve children with and without Down syndrome (DS) performed eight subtests of an apraxia battery to determine under what conditions children with DS had difficulty performing representational and nonrepresentational gestures. Participants with DS also completed a dichotic listening test. Participants with DS performed just as well as control participants on all aspects of the apraxia battery except a subtest in which they were required to pantomime tool use from verbal instruction. This suggests that children with DS have difficulty generating an action from memory following verbal instruction. Given the sufficient context or visual demonstration, children with DS performed similar to the other participants. As well, there was a great deal of within-group variability for dichotic listening ear advantage. Participants with a greater left ear advantage on the dichotic listening test committed more errors on an imitation test that also included a verbal component than participants with a greater right ear advantage.

Keywords:

• Down syndrome
• apraxia
• speech
• motor control
• gestures

This research was cofunded by the National Down Syndrome Society and the National Institute of Child Health and Human Development (National Institute of Health Grant 1R01 HD37448-01). We also acknowledge the support of the Canada Research Chair program. This work was part of the first author's MS thesis conducted under the supervision of the second and third authors.

We thank the children and parents who, not only volunteered their time, but who participated enthusiastically in this research.

We wish to recognize the hard work of research assistants Victoria Dhillon and Cheryl Glazebrook who assisted with scoring the apraxia battery from this project.

Special thanks also to the staff at the Down Syndrome Research Foundation, the Hamilton Down Syndrome Association, Express Yourself Communication Services, the McMaster Children's Centre, and the Department of Athletics and Recreation at McMaster University.

Notes

¹The “thumbs up” gesture was substituted for the “ok” gesture in the original battery because it was thought to be less complex.

²It was assumed that the receptive language of the participants without Down syndrome was equivalent to their chronological age.

³Two sections of the Apraxia Battery (Tool Identification, Object Use) were not included in the analysis. These sections were essentially used to screen the participants to make sure they could correctly 1.) identify the tools used in the battery from a group of pictures including distractors, and 2.) identify, from a group of pictures, the tools used to perform specific actions. Participants that made mistakes in the initial screening were given the correct answer and then retested. The majority of participants did not make any mistakes on these two sections of the battery.

⁴A dichotic listening protocol was only used to test participants with Down syndrome because the results of numerous studies have shown that mean Laterality Indices generated from participants with Down syndrome consistently differ from those of participants without Down syndrome (see Elliott & Weeks, 1994 for a meta analysis). Specifically, individuals without Down syndrome exhibit a right ear advantage-left hemisphere advantage for speech perception while individuals with Down syndrome usually exhibit a left ear-right hemisphere advantage for speech perception.

⁵A selective listening protocol was not used because it was thought that the instructions for a free recall protocol would be much easier for young children to understand. Past research involving persons with DS suggests that results derived from the two dichotic listening protocols are not different (Giencke & Lewandowski, 1989).