Changes in movement transitions across a practice period in childhood apraxia of speech.

This study examined changes in speech motor control across a movement transition between sounds within a motor learning task in children with apraxia of speech (CAS) and typical development (TD). It was investigated whether oral articulator movement was refined with practice and whether practice gains generalized to words not included in the practice session. A total of 16 children (ages 5-6) with CAS (n = 8) and TD (n = 8) participated in this study. Novel and real word tokens were produced at three time points. Kinematic data was collected using facial motion tracking at each time point. Children completed a practice session following baseline data collection session that integrated motor learning principles. Three tokens were included in the practice session and the remaining stimuli assessed carryover of practice gains. Kinematic data was then collected immediately following practice and 3 days later. Kinematic analyses were conducted on the movement gesture for the first syllable of each word. Narrow transcription analyses examined speech production accuracy. Children in the CAS group displayed increased consonant and vowel accuracy only for the practised tokens. Adjustments to spatial control and movement variability were observed in the CAS group, though only for practised words. Children in the TD group altered spatial and temporal domains of movement and variability across both practised and non-practised tokens. Interestingly, the CAS group displayed a pattern of increased displacement along with decreased variability, which was not observed in the TD group. The degree to which these findings reflect facilitative or maladaptive changes are discussed. Results are also interpreted in relation to vowel properties, novel/real word status and variable practice of novel and real words.