Generalisation of a novel implicit treatment for coarse coding deficit in right hemisphere brain damage: A single-participant experiment

Abstract

Background: This manuscript reports generalisation effects of Contextual Constraint Treatment for an adult with right hemisphere brain damage (RHD). Contextual Constraint Treatment is designed to stimulate inefficient language comprehension processes implicitly, by providing linguistic context to prime, or constrain, the intended interpretations of treatment stimuli. The study participant had a coarse coding deficit, defined as delayed mental activation of particularly distant semantic features of words (e.g., rotten as a feature of “apple”). Treatment effects were expected to generalise to auditory comprehension of narrative discourse, and perhaps to figurative language interpretation, because coarse coding has been hypothesised and/or demonstrated to support these abilities. Aims: This treatment study aimed to induce generalisation of Contextual Constraint Treatment in an adult with RHD with inefficient coarse coding. Methods & Procedures: The participant in this study was a 75-year-old man with RHD and a coarse coding deficit. A single-participant experimental design across behaviours (stimulus lists) was used to document performance in baseline, treatment, and follow-up phases. Treatment consisted of providing brief, spoken context sentences to prestimulate, or constrain, intended interpretations of stimulus items. The participant made no explicit associations or metalinguistic judgements about the constraint sentences or stimulus words; rather these contexts served only as implicit primes. Probe tasks were adapted from prior work on coarse coding in RHD. The dependent measure was the percentage of responses that met predetermined response time criteria. There were two levels of contextual constraint, Strong and Moderate. Treatment for each item began with the provision of the Strong constraint context, to minimise the production or reinforcement of erroneous or exceedingly slow responses. Generalisation was assessed to a well-standardised measure of narrative discourse comprehension and to several metalinguistic tasks of figurative language interpretation. Outcomes & Results: Treatment-contingent gains, associated with respectable effect sizes, were evident after a brief period of treatment on one stimulus list. Generalisation occurred to untrained items, suggesting that the treatment was facilitating the underlying coarse coding process. Most importantly, generalisation was evident to narrative comprehension performance, for both overall accuracy and accuracy in answering questions about implied information, and all of these gains were maintained through three follow-up sessions. Conclusions: Although the results are still preliminary, this single-participant experimental design documents the potential for meaningful gains from a novel treatment that implicitly targets an underlying language comprehension process in an adult with RHD.