In March 2013 I described the research we are conducting in my lab to identify individual differences in response to two different approaches to the treatment of Childhood Apraxia of Speech. I also described the unique single subject randomization design that we are using and presented some data for one child without revealing the interventions that corresponded to the condition that worked best for this particular child. We have subsequently replicated this result with another child so today I am going to write about the features of the intervention that children with difficulties in the area of transcoding appear to benefit from most clearly. Recall that transcoding is revealed in part by addition errors on the Syllable Repetition Task. In the case of the child profiled in the previous blog, he added nasal consonants at syllable boundaries when asked to repeat the syllable strings and he was just as likely to do this for short strings as for long, e.g., “mada” → [bᴂndə] and “manabada” → [mandabad]. This child also had difficulty with multisyllable repetition during the maximum performance tests but no difficulty with the single syllable diadochokinetic rate. Within word inconsistency was borderline with inconsistent word productions largely reflecting single feature errors (voicing errors for example). Altogether the impression is of a true apraxia or motor planning disorder (as opposed to a phonological planning deficit, a more common problem that I will describe in a future post). Thus far we have assessed 18 children in this study and remarkably only 3 have presented with this particular profile.

Two of these children have shown the best response to an intervention that is directed at promoting auditory-motor integration. It includes input-oriented procedures that are described in Chapter 9 of my book combined with output-oriented procedures described in Chapter 10. The procedures are used to promote the consistent use of stimulable phonemes in the context of word shapes that are difficult for the child so that the focus is more on holistic movement patterns at the whole word level than on individual phonemes. In the case described here we taught novel “monster names” that had a strong-weak-strong stress pattern and word internal coda consonants such as “Biftenope” and “Hapnidreem” and assessed for carry-over to phrases with similar structures (pumpkin pie, bat mobile). 

One reason that we designed an intervention approach that focused on auditory-motor integration is that there is evidence from the animal literature suggesting that this might be a foundational problem in the case of apraxia. Kurt, Fisher and Ehret examined sensory-motor association learning in mice with two different FoxP2 mutations. The task involved learning to avoid electronic shock by leaping a hurdle (or not) to the other compartment of a box in response to varied tones that signaled the location of the shock. Mice with either mutation were impaired in their response, one more severe that the other, in comparison to wild-type mice that learned the task without difficulty. The second reason that we designed an intervention with an auditory-motor integration component is that the ability to modify motor plans in response to auditory feedback and in relation to an auditory target is theoretically essential to the acquisition of speech motor control.

So what does an intervention that focuses on auditory-motor integration look like? Not surprisingly it has procedures that focus attention on the auditory-perceptual aspects of speech as well as procedures that focus on motor practice, none of the procedures themselves being novel or surprising. During the prepractice portion of each treatment we ensured that the child had a good perceptual representation for the target words using auditory bombardment and focused stimulation in meaningful contexts as well as error detection tasks as described in my teaching blog (scroll down to week 22). We also taught the child to monitor his own speech and respond differentially to his own correct or incorrect productions of the target words. For example an appropriate activity might be for the child “call” the monster and to then place the monster in his sleeping bag in the tent if he heard himself produce the name correctly or to place the monster in an alternative sleeping bag out in the rain if he heard himself produce the name incorrectly (our students are endlessly creative and this variation on the game has proved to be popular with the children this year).  The practice part of the session, for the most part, proceeds as one would expect for any child with CAS, focusing on high intensity practice while the SLP provides just enough stimulation prior to each attempt to elicit a correct response more often than not. However, every effort is made to avoid providing too much feedback. Working in blocks of five trials each, summative knowledge of results is provided whenever possible – this means that the child is given an opportunity to evaluate his own responses in relation to his own auditory goal without interference from SLP input, and then compare his own judgment with the SLPs count of correct responses at the end of each 5 trial run. Edy Strand writes about the importance of giving the child time to integrate feedback in her chapter with Derbertine in Caruso and Strand (1999) and describes precisely how to do this. Given a high rate of responses (over 100 trials per 20 minute practice session) and an average of 70% correct responses, this child was able to make excellent progress as measured by both same day and next day probes (see green bars on his chart here). A second child with the same profile also showed a significant benefit in favour of this approach. A third child is still being treated and it will be some time before we will know if he completes the protocol and then many more months before blind coding of his results will be finished. But, we are hopeful!