Tongue movements in adults, children and speakers with developmental
apraxia of speech

Tanja Kocjancic, Edinburgh

Developmental apraxia of speech (DAS) is a neurological motor speech
disorder caused by a disruption at the motor planning level and resulting
in an impairment of executing volitional speech movements.  The cause of
the disorder is not known and there is no agreed set of speech
characteristics. However, the most commonly reported ones are
unintelligible speech, presence of consonant and vowel errors, high
inconsistency of speech production, impaired prosody, groping, sequencing
difficulties with phonemes and syllables. Recent studies suggest that
speakers with DAS exhibit impairment at the syllable planning level
(Maassen et al. 2001, Nijland et al. 2003, 2004) and timing deficit
(Shriberg et al. 2003, Peter & Stoel-Gammon 2005). The aim of the present
study is to use ultrasound imaging to describe tongue movements of
speakers with DAS and control groups in terms of the distance the tongue
travels over syllables with different onset complexity, the time needed
and the overall speed. Three teenagers with DAS, ten typically speaking
adults (20-30 years) and ten typically developing children (6-9 years)
participated in the study. Each speaker made five repetitions of six
syllables differing in the syllable onset structure: pay, say, lay, play,
slay, splay. Group results show that while both adults and typically
developing children exhibit  an effect of syllable structure on the three
measurements, DAS speakers do not. Over all syllable targets, DAS speaker
showed longer durations than adults but shorter than children, shorter
distance of tongue travel than the other two groups and lower speed of
tongue travel. Such results suggest that ultrasound enables observing the
influence of onset structure  on tongue movements and that it can
differentiate speakers with DAS from adults and typically developing
children.