Purpose: Speech motor skill is refined over the course of practice, which is commonly reflected by increased accuracy and consistency. This research examined the relationship between auditory-perceptual ratings of word accuracy and measures of speech motor timing and variability at pre- and posttreatment in children with childhood apraxia of speech (CAS). Furthermore, the degree to which individual patterns of baseline probe word accuracy, receptive language, and cognition predicted response to treatment was explored.
Method: Probe data were collected from seven children with CAS (aged 2;5-5;0 [years;months]) who received 6 weeks of Dynamic Temporal and Tactile Cueing (DTTC) treatment. Using a multidimensional approach to measuring speech performance, auditory-perceptual (whole-word accuracy), acoustic (whole-word duration), and kinematic (jaw movement variability) analyses were conducted on probe words produced pre- and posttreatment. Standardized tests of receptive language and cognition were administered pretreatment.
Results: There was a negative relationship between auditory-perceptual measures of word accuracy and movement variability. Higher word accuracy was associated with lower jaw movement variability following intervention. There was a strong relationship between word accuracy and word duration at baseline, which became less robust posttreatment. Furthermore, baseline word accuracy was the only child-specific factor to predict response to DTTC treatment.
Conclusions: Following a period of motor-based intervention, children with CAS appeared to refine speech motor control in conjunction with improvements in word accuracy. Those who demonstrated the poorest performance at treatment onset displayed the greatest degree of gains. Taken together, these results reflect a system-wide change following motor-based intervention.