Journal Review: apraxia of speech

Reference: Aichert, I and Zeigler, W. (2013) Segments and syllables in the treatment of apraxia of speech: An investigation of learning and transfer effects.

Background information

·   Isolated phonemes are often used as targets in the treatment of severe AOS.

·   Isolated phoneme’s however occur rarely in natural speech and do not play a role in language acquisition (bablling is based on syllabic units).

·   The syllable is assumed to be the basic unit of articulatory programming in speech.

·   Levelt et al (1999) – Phonetic level – there is a long-term store of motor patterns for frequently occurring syllables.

·   AOS – syllable structure and frequency impact on production accuracy.

·   Hypothesis: In AOS patients have access to a mental syllabary but the motor programs stored there are partially destroyed.

Study Question

·   Which out of segments or syllables (both phonological units) can be more efficiently trained in patient’s with severe AOS.

·   Learning effects and transfer effects into larger units were analysed.

Methods

·   4 patients used with AOS diagnosis (diagnosed by looking at spontaneous speech and repetition) + associated aphasia.

·   Diagnosis (Zeigler 2008): 1. Presence of phonemic errors (e.g. substitutions/omissions) 2. Inconsistent occurrence of phonetic distortions 3. Dysfluency due to: inter/intrasyllabic pauses, phoneme lengthenings, groping/repairs.

·   Screening lists of syllables + consonants were administered (target+control syllables/consonants).

Therapy

·   Four 45 minute sessions a week.

·   Segments/syllables presented orally and visually in a repetition + reading aloud format.

·   Feedback was given regularly e.g. auditory stimulation, visual cues (therapists mouth shape), and tactile/kinesthetic cues were given.

·   Syllables were always trained as a whole.

Results

·   Only one patient did not improve – they were the only patient to demonstrate severe perseveration.

·   Clear advantage of syllable training rather than segmental training. ¾ patients improved on target syllables, 2/4 showed transfer effects compared to ¼ and 0/4 for segmental training.

Key discussion points

·   Communicative expressions with single vowels/dipthongs/consonants which do constitute natural speech units e.g. sh, mm, ah, ai = good candidates to facilitate first speech sounds in patients with severe AOS.

·   The coarticulation of consonants with vowels (this occurs in syllables) is likely to be in the speech motor plan that needs to be re-learned. This has been found in several studies.

·   Transfer effect was noted form single syllables – two syllable words.

·   Perseveration may be due to disinhibited speech motor programs, when defective phonetic encoding fails to generate new motor patterns.

·   Different treatment protocals could be chosen for patient’s who perseverate.

Criticisms

·   Small cohort.

·   Multiple factors such as degree of aphasia could impact on the results.

·   Segments and syllables tend to be trained together and embedded in words.

Learning Outocomes

·   Perseveration – negative prognositic indicator – consider a different treatment protocal e.g. more participation based.

·   Train syllables rather than phonemes and try to use communicative individual segments to begin with e.g. mm, ah, ai…..