Testing Client Response to Alternative Speech Therapies

Buchwald et al published one of the many interesting papers in a recent special issue on motor speech disorders in the Journal of Speech, Language and Hearing Research. In their paper they outline a common approach to speech production, one that is illustrated and discussed in some detail in Chapters 3 and 7 of our book, Developmental Phonological Disorders: Foundations of Clinical Practice. Buchwald et al. apply it in the context of Acquired Apraxia of Speech however. They distinguish between patients who produce speech errors subsequent to left hemisphere cardiovascular accident as a consequence of motor planning difficulties versus phonological planning difficulties. Specifically, in their study there are four such patients, two in each subgroup. Acoustic analysis was used to determine whether their cluster errors arose during phonological planning or in the next stage of speech production – during motor planning. The analysis involves comparing the durations of segments in triads of words like this: /skæmp/ → [skæmp], /skæmp/ → [skæm], /skæm/ → [skæm]. The basic idea is that if segments such as [k] in /sk/ → [k] or [m] in /mp/ → [m] are produced as they would be in a singleton context, then the errors arise during phonological planning; alternatively, if they are produced as they would be in the cluster context, then the deletion errors arise during motor planning. This leads the authors to hypothesize that patients with these different error types would respond differently to intervention. So they treated all four patients with the same treatment, described as “repetition based speech motor learning practice”. Consistent with their hypothesis, the two patients with motor planning errors responded to this treatment and the two with phonological planning errors did not as shown in the table of pre- versus post-treatment results.

Buchwald et al results corrected table

However, as the authors point out, a significant limitation of this study is that the design is not experimental. Having failed to establish experimental control either within or across speakers it is difficult to draw conclusions.

I find the paper to be of interest on two accounts nonetheless. Firstly, their hypothesis is exactly the same hypothesis that Tanya Matthews and I posed for children who present with phonological versus motor planning deficits. Secondly, their hypothesis is fully compatible with the application of a single subject randomization design. Therefore it provides me with an opportunity to follow through with my promise from the previous blog, to demonstrate how to set up this design for clinical research.

For her dissertation research, Tanya identified 11 children with severe speech disorders and inconsistent speech sound errors who completed our full experimental paradigm. These children were diagnosed with either a phonological planning disorder or a motor planning disorder using the Syllable Repetition Task and other assessments as described in our recently CJSLPA paper, available open access here. Using those procedures, we found that 6 had a motor planning deficit and 5 had a phonological planning deficit.

Then we hypothesized that the children with motor planning disorders would respond to a treatment that targeted speech motor control: much like Brumbach et al., it included repetition practice according to the principles of motor practice during the practice parts of the session but during prepractice, children were taught to identify the target words and to identify mispronunciations of the target words so that they would be better able to integrate feedback and self-correct during repetition practice. Notice that direct and delayed imitation are important procedures in this approach. We called this the auditory-motor integration (AMI approach).

For children with Phonological Planning disorders we hypothesized that they would respond to a treatment similar to the principles suggested by Dodd et al (i.e., see core vocabulary approach). Specifically the children are taught to segment the target words into phonemes, associating the phonemes with visual cues. Then we taught the children to chain the phonemes back together into a single word. Finally, during the practice component of each session, we encouraged the children to produce the words using the visual cues when necessary. An important component of this approach is that auditory-visual models are not provided prior to the child’s production attempt-the child is forced to construct the phonological plan independently. We called this the phonological memory & planning (PMP) approach.

We also had a control condition that consisted solely of repetition practice (CON condition).

The big difference between our work and Brumbach et al. is that we tested our hypothesis using a single subject block randomization design, as described in our recent tutorial in Journal of Communication Disorders. The design was set up so that each of the 11 children experienced all three treatments. We chose 3 treatment targets for each child, randomly assigned the targets to each of the three treatments, and then randomly assigned the treatments to each of three sessions, scheduled to occur on different days of the week, 3 sessions per week for 6 weeks. You can see from the table below that each week counts as one block, so there are 6 blocks of 3 sessions for 18 sessions in total. The randomization scheme was generated blindly and independently using computer software for each child. The diagram below shows the treatment schedule for one of the children with a motor planning disorder.

Block Randomization TASC02 DPD Blog

This design allowed us to compare response to the three treatments within each child using a randomization test. For this child, the randomization test revealed a highly significant difference in favour of the AMI treatment as compared to the PMP treatment, as hypothesized for children with motor planning deficits. I don’t want to scoop Tanya’s thesis because she will finish it soon, before the end of 2017 I’m sure, but the long and the short of it is that we have a very clear results in favour of our hypothesis using this fully experimental design and the statistics that are licensed by it. I hope you will check out our tutorial on the application of this design: we show how flexible and versatile this design can be for addressing many different questions about speech-language practice. There is much exciting work being done in the area of speech motor control and this is a design that gives researchers and clinicians an opportunity to obtain interpretable results with small samples of children with rare or idiosyncratic profiles.

Reading

Buchwald, A., & Miozzo, M. (2012). Phonological and Motor Errors in Individuals With Acquired Sound Production Impairment. Journal of Speech, Language, and Hearing Research, 55(5), S1573-S1586. doi:10.1044/1092-4388(2012/11-0200)

Rvachew, S., & Matthews, T. (2017). Using the Syllable Repetition Task to Reveal Underlying Speech Processes in Childhood Apraxia of Speech: A Tutorial. Canadian Journal of Speech-Language Pathology and Audiology, 41(1), 106-126.

Rvachew, S., & Matthews, T. (2017). Demonstrating treatment efficacy using the single subject randomization design: A tutorial and demonstration. Journal of Communication Disorders, 67, 1-13. doi:https://doi.org/10.1016/j.jcomdis.2017.04.003

 

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Phonological Memory and Phonological Planning

I have been writing about the children in our intervention study for children with Childhood Apraxia of Speech (CAS). So far about half of the children referred to us appear to have difficulties in the domain of phonological memory with their overt phenotype corresponding to the subtype described by Dorothy Bishop Dodd as Inconsistent Deviant Disorder. Shriberg et al. (2012) have developed the Syllable Repetition Task as one means of identifying deficits in “memory processes that store and retrieve [phonemic, sublexical, and lexical] representations. We have been using this SRT test to differentiate children who have deficits in phonological planning versus motor planning. I described the profile that corresponds to difficulties with motor planning (transcoding) in a previous post. Today I will discuss the phonological memory or phonological planning profile that we see in approximately half of the children that are referred to us with suspected CAS.

These children can be identified by a qualitative analysis of their SRT performance and by their performance on the Inconsistency Test of the DEAP. Starting with the SRT, one child in our study for example was able to achieve 12/18 consonants correct when imitating 2-syllable items but only 5/18 consonants correct when imitating 3-syllable items, thus exemplifying the classic profile of a child with phonological memory difficulties – better nonword repetition performance for short versus long items. Qualitatively he tended toward consonant harmony errors even with some 2-syllable items, /bama/=[mama],  /maba/=[mama],  and then more frequently with the 3-syllable items, /nabada/=[mamada]. Addition of syllables and vowel errors also occurred, /manaba/ = [mamadada],  /manabada/=[mimadama]. Poor maintenance of phonotactic structure and vowel errors were also observed on the Inconsistency Test, “helicopter” = [hokopapɚ], “elephant”= [ɛmpɩnt], which yielded an overall inconsistency score of 78% as many words were produced with multiple variants, e.g., “butterfly”= [bʌtfaɩ], [bʌtwaɩ], [bʌtətwaɩ].

The most striking illustration of the difficulties these children have with the storage and retrieval of phonological representations comes during our treatment sessions however. In this research program we are teaching the children nonsense words in meaningful contexts. For example in one scenario we teach the children the names of “alien flowers” and in one of the treatment conditions we use graphic stimuli, paired with gestural cues if necessary, to represent the syllables and phonemes in the words and phrases that we are teaching. Many of the children in our study learn all of the nonsense words without difficulty (5 words per goal/condition introduced over 6 45-minute sessions). However children with the phonological memory difficulties have great difficulty learning the words (SLP: This is a speet. Say speet. Child: speet. That’s right, speet. What is it? Child: I don’t know. SLP: Yes, you do it’s speet, the purple one, the purple one is speet, remember, say speet. Child: ‘speet’. SLP, you’ve got it, the purple flower is speet, it’s a speet, what is it, it’s a … Child: um, I don’t know, and so on).

Image

The most effective intervention to use with these children closely mirrors the procedures described by Barbara Dodd as the “core vocabulary” approach and demonstrated by Sharon Crosbie in the video that accompanies their chapter in the Williams, McLeod and McCauley (2010) book. The video is lovely and shows how to use graphic stimuli and a chaining procedure to teach the child to produce a word consistently – the idea is to encourage the child to develop and implement their own phonological/motor plan rather than relying on an imitative model. The children respond to this technique really well and will learn to say the new words such as “speet” and “stoon” quickly and accurately. The trouble begins when our student SLPs want the children to use the new words spontaneously in phrases (e.g., “water the speet”). They have great difficulty remembering the word or even the carrier phrase without the imitative model and I have to work really hard to teach the student clinicians to withhold the imitative model in favour of using other cues to stimulate spontaneous production of the target words and phrases (SLP: What is it? Let’s start with the snake sound here…).

We have wonderful video of student SLPs learning these techniques as well as children achieving their goals. Tanya Matthews and I will be presenting them at ASHA 2014. The difference in the way that you implement therapy with these children is subtle but important. I am pretty sure that Case Study 8-4 in our book had a phonological planning deficit rather than the motor planning disorder that he was treated for. I can’t help but think that if he was treated with these techniques he might have made some progress in the three years that we followed his case (whereas he made literally no progress at all until he was treated with a synthetic phonics approach in second grade). I’d love to hear from you if you have any other ideas about how best to treat children with phonological memory problems and inconsistent deviant disorder.