Using Orthographic Representations in Speech and Language Therapy

Word learning, and in particular, productive word learning is associated with three important processes in the phonological domain: first, the child must encode the acoustic-phonetic form of the word in the language input; second the child must transform this representation into a lexical representation, generally considered to take on a more abstract phonological form; finally the child must retrieve the representation to reproduce it. The first process is reliant on speech processing abilities that have been shown to be impaired in many children with speech, language and reading deficits, as shown by for example by Ben Munson and colleages (@benjyraymunson) and Nina Kraus and colleages. Phonological encoding is enhanced by access to repeated high-quality but variable inputs as shown by Richtmeier et al for normally developing children and by Rice et al for children with SLI. The majority of children with SSD have difficulties with encoding: we have a paper in press with the American Journal of Speech-Language Pathology showing that speech accuracy in these children can be improved with an approach that focuses largely on the provision of intense high quality input – I will have more to say on this subject when it (finally) emerges in print.

The second process, forming a phonological representation and storing it in the lexicon, involves articulatory recoding which can be a serious problem for children with severe SSD, accounting for deficits in speech accuracy (especially in association with inconsistency), nonword repetition, word learning, productive vocabulary, word finding, rapid automatic naming, and other phonological processing skills. These children are often diagnosed with motor planning disorders but I have pointed out previously that the problem is actually at the level of phonological planning. I have further pointed out the very close relationship between speech planning and memory. Children who are having difficulty with phonological planning may not show the same benefit from a therapy approach that is focused on the provision of high quality inputs. Therefore a new paper on the use of orthographic inputs to teach new words caught my eye.  Ricketts et al taught children with SLI and ASD as well as younger and age-matched children with typical language to label nonsense objects with new names, using a computer program. For some words, the children were exposed only to the object–auditory word pairing; for others they saw the object, heard the word and saw a printed version (orthographic representation) as well. All children found it easier to learn the new words when they were exposed to the orthographic representation along with the auditory word.

This study reminded me of the research we are doing with children who are referred to our clinic with an apraxia diagnosis due to inconsistent speech errors. So far, 40% of those children have difficulty with phonological planning rather than motor planning as revealed by the syllable repetition test, as I have explained in a previous blog. We have been using a single subject randomization design to compare the relative efficacy of two treatment approaches with these children. The Phonological Memory & Planning (PMP) intervention pairs the phonemes in the target words with visual referents that include letters as shown here. Imitative models are avoided and the child is encouraged to create their own phonological plan and produce the word using the visual symbols when necessary. An alternative treatment, the Auditory-Motor Integration (AMI) Treatment is quite different with a heavy emphasis on prior auditory stimulation and self-judgments of the match between auditory inputs and outputs. A third condition is a usual care CONtrol condition focusing on high intensity practice. In all cases we teach nonsense words paired with real objects, with the words structured to target the children’s phonological needs in the segmental and prosodic domains.

The results are assessed by applying a resampling test to probe scores and then combining p-values across the children. These are the statistical results (F and t tests by resampling test) for the Same Day Probe Scores, with p-values combined across the 5 children who have proven to have phonological planning problems in concert with a severe inconsistent speech disorder:

TASC PMP results Aug 2015

The results in the third column show that all of the children obtained a significant treatment effect. The findings in the remaining columns pertain to planned comparisons with positive t values being in the expected direction. The combined p values indicate that all treatments are significantly different from each other and inspection of the mean scores across children show that the pattern of results is PMP > CON > AMI. The result is made more interesting by the fact that the pattern of results is the exact opposite for children with a motor planning disorder. Tanya Matthews and I will compare these two subgroups with data and video during our presentation at ASHA 2016 in Denver this coming fall.

Session Number: 1429
Session Title: Differential Diagnosis of Severe Phonological Disorder & Childhood Apraxia of Speech
Day: Friday, November 13, 2015
Time: 1:00 PM – 3:00 PM
Session Format: Seminar 2-hours

For now, the take away message is that learning new words involves (at least) three important processes: encoding the sound of the new word, memory processes for storing and retrieving the phonological representation and motor planning processes for planning and programming articulatory movements prior to production of the new word. There are published studies showing that intervention procedures targeting each of these processes help children with speech, language and reading difficulties. Increasing frequency of high quality input improves quality of the acoustic-phonetic representation. Pairing phonological segments with visual symbols helps with storage and retrieval of the phonological representation. High intensity speech practice with appropriate stimulation and feedback improves motor planning and motor programming. The trick is to figure out which children require which procedures at which time.

AOS, CAS and STM

I greatly enjoyed this new Frontiers in Neuroscience paper by Hickok and colleagues called “Partially overlapping sensorimotor networks underlie speech praxis and verbal short-term memory: Evidence from apraxia of speech following acute stroke”. These researchers evaluated 76 patients during the acute phase of their stroke using behavioral and MRI measures. They found a strong relationship between apraxia (AOS) and verbal short- term memory (vSTM) difficulties as well as weak relationships between aphasia and AOS and vSTM upon behavioral testing. For patients with AOS, the MRIs revealed tissue damage along a sensorimotor network of motor-related areas and sensory-related areas. The motor related areas that were implicated were as follows: primary motor cortex (proposed site of motor programs for opening and closing vocal tract gestures that correspond roughly to consonant and vowel phonemes); pars opercularis (a part of Broca’s area involved in phonological processing and suppression of response tendencies);  premotor cortex (planning and sequencing of speech units and sensory guidance of movement; motor programs for syllables); and insula (specialized for motor planning of speech). The sensory-related areas  associated with AOS were primary somatosensory cortex (site of  somatosensory targets for speech); secondary somatosensory cortex (sensorimotor integration); parietal operculum (sensory motor interface for speech); and auditory cortex (processing of auditory information; auditory targets for speech). The areas associated with vSTM deficits overlapped those associated with AOS but only in the motor-related areas, specifically pars opercularis and par triangularis (i.e., Broca’s area), premotor cortex and primary motor cortex.

With regard to the network associated with AOS, the authors concluded that the findings demonstrate “that the targets for speech are sensory in nature” and that “motor control generally and speech motor control specifically is dependent on sensorimotor integration”. I found these conclusions to be interesting in view of our interventions studies with children who have childhood apraxia of speech. As I reported in a previous blog, we are having success with an approach in which we encourage strengthening of both articulatory-phonetic and acoustic-phonetic representations for target words and the connections between them.

With regard to vSTM, the authors indicate that “the involvement of motor areas is predicted as vSTM involves an articulatory rehearsal component”. They seem  surprised however that “posterior, sensory related regions” were not implicated in this study as correlates of the hypothesized “storage” component in short-term memory. This finding reminded me of a paper I wrote in 2008 in which I pointed out that children’s nonword repetition performance, supposedly a measure of vSTM, factors with speech production accuracy rather than language ability in large scale studies involving children with either typical or atypical language development. I interpreted these findings in relation to a connectionist model of working memory proposed by MacDonald and Christensen (2002). According to this model there is no short term memory store per se because  working memory is not differentiated from linguistic knowledge and processing. Individual differences in working memory task performance reflect differences in precision of phonological representations and processing efficiency due to experiential and biological factors. The processes and representations involved in working memory are the same as those used in speech planning.  Many of the children that we are working with have difficulty planning an utterance – I have described these children with phonological planning difficulties in a previous blog. The children have difficulty with consistent repetition of nonwords and complex real words. The successful intervention for these children involves providing multimodal external cues to support the child’s efforts to construct and execute a plan to produce new words, as described in a previous blog. It is important that the SLP avoid providing an auditory  model for imitation by the child however although the SLP may imitate the child’s production to reinforce successful attempts or correct failed attempts.

Hickok et al interpret their findings in light of their hierarchical model although I remain uncertain about this notion of a hierarchical organization of these components just because I can never quite sort out what ‘higher” versus “lower” means when placing these kinds of components in a hierarchical relationship.  The importance of acquiring knowledge of different forms of linguistic representation – acoustic, articulatory, phonological and semantic – and linking across multiple representations to achieve functional goals has implications for typical and atypical language development however.

Tanya and I will be discussing these issues further (with video demonstrations) at ASHA2014:

Topic Area: Speech Sound Disorders in Children Session Number: 1037 Title: Differential Diagnosis of Severe Phonological Disorder & Childhood Apraxia of Speech Session Format: Seminar 2-hours Day: Thursday, November 20, 2014 Time: 10:30 AM ─ 12:30 PM Author(s): Susan Rvachew and Tanya Matthews