Children with apraxia of speech (CAS) often display slow progress during speech treatment, which includes difficulty acquiring, retaining and generalizing new skills. In August 2012, CASANA awarded a competitive research grant to Dr. Maria Grigos and Ms. Julie Case of the Department of Communicative Sciences and Disorders at New York University. Funds from this grant were used towards their study of speech motor learning in children with CAS and children with typically developing speech and language skills (TD). The aims of this research were to explore how children learn novel speech targets and maintain newly acquired skills.
Facial tracking technology was used to investigate changes in speech production and articulatory control while children practiced novel words. Sixteen children between the ages of five and six years participated in the study: eight children with CAS and eight TD controls. Novel words were presented to the children at the beginning of the experiment. These words were produced at three different time periods: baseline, short-term, and long-term. Baseline represented the very first time children produced the novel words and was followed by an intense practice session designed according to principles of motor learning. Following this practice session, short-term change was measured. Children then returned three days later to assess long-term retention. These time periods were selected to capture speech production changes within a therapy session (i.e., short term change), as well as between sessions (i.e. long term retention). A three-day time period was selected to represent a typical lapse between therapy sessions.
The children with CAS displayed short- and long-term improvements in consonant/vowel accuracy and consistency; however, their performance remained consistently poorer than the TD control group. Articulatory control was examined during accurate word productions. The children with CAS demonstrated longer duration of jaw movement than TD controls across each of the three time periods. Further, articulator movement variability remained high in the CAS group across all sessions, while children in the TD group produced more stable movements. In other words, children with CAS took more time to move their articulators and did so more variably than the TD controls as they produced novel words.
The main finding from this research is that children with CAS showed improved consonant/vowel accuracy and consistency with practice, while their underlying movement patterns did not change. This result is particularly interesting as children with CAS often make slow progress in treatment and have difficulty generalizing treatment gains. During treatment, a child with CAS may improve sound production and appear to be making steady gains; however, increases in consonant/vowel accuracy alone may not reflect changes in the underlying movement patterns. Refined articulatory control may be required in order to maintain and generalize improved speech patterns. Additional work is needed to better understand the type and amount of practice required for long-term speech production changes to occur. Such research will contribute to our understanding of why certain treatment techniques are more effective for children with CAS than others.