Implicit phoneme manipulation for the treatment of apraxia of speech and co‐occurring aphasia

Abstract

Background: Apraxia of speech (AOS) is a disorder of expressive speech attributed to an impairment at the motor planning and programming phases of speech production. AOS is treated in different ways but the articulatory kinematic approach is usually followed. The intervention described in this study introduces a new approach toward treatment of AOS with aphasia through the use of implicit manipulation of phonemes via rhyming, deletion and alliteration tasks. Theoretical models propose that during lexical retrieval, associated areas responsible for motor planning and the preparation of the utterance are activated. In a similar way, our tasks require a phoneme manipulation that is hypothesised to activate motor planning. The repeated implicit practice of retrieving and internally monitoring sounds in various phonetic contexts may improve the efficiency of the transition between phonological plans and the initial phase of motor planning and the monitoring of that plan. Therefore, if AOS is due to a dysfunction of motor planning, an implicit intervention targeting this phase may improve speech production without the need for overt practice. Methods and Procedures: This single‐subject multiple baseline intervention used implicit phoneme manipulation tasks in a subject with AOS and mild aphasia. The therapist‐designed computerised program required the subject to perform the implicit practice of rhyming, deletion, and alliteration of phonemes in three sound classes: /ʃ/, /ʤ/, and /s/ clusters in various phonetic contexts. Stimuli were presented on computerised templates requiring the subject to select the target among 3 foils. No overt speech was required however probe word repetitions were necessary to monitor treatment effects. Outcomes and Results: The effect sizes for the trained words were: /ʃ/ probes d = 4.46, /ʤ/ probes d = 6.02, and /s/ clusters d = 2.54 which represents a small to medium effect for /ʃ/ and /ʤ/. T‐MAC results of 59/87 (68%) at pre‐testing improved to 75/87 (87%) at post‐test (z = 3.08, binomial p < .01, two‐tailed) which suggest generalisation to non‐treatment words. Patterns of change in three probe words over the course of treatment suggest an improvement in speech production. Distortions, disturbed prosody and phonological errors were resolved in these probes by the maintenance session as judged by 5 SLPs. Conclusions: We conclude that in this participant (1) implicit phoneme manipulation training improved overt speech production; (2) accuracy of trained words, specifically a reduction in sound distortions, phonological errors and improved prosody, were the result of this treatment; and (3) a significant generalisation to non‐treatment words was the result of the intervention.