Rehabilitation of phonological and semantic control in aphasia: an fMRI case study

Aphasic patients may suffer from phonological or semantic inhibitory control deficits which are characterized by difficulties at the level of verbal inhibition and working memory. Very few treatment methods are available for this type of deficit. We investigated the feasibility of a phonological control treatment program in an aphasic patient, at both behavioural and neural levels. CT (77 years old) presented with aphasic symptoms characterized by verbal inhibition deficits in various language and verbal memory tasks. Phonological control was trained with a series of tasks in which CT had to name a stimulus while inhibiting a phonological distractor presented along with the target. Baseline measures were obtained via a word immediate serial task, with both trained and untrained words. CT and 34 control subjects also completed a phonological and a semantic inhibition task in an MRI scanner. At the end of the training program, CT’s performance had significantly improved, for both treated and untreated words , suggesting a transfer effect of phonological inhibitory training rather than spontaneous recovery given that CT’s performance was still impaired in semantic inhibitory tasks (as well as other phonological control tasks). A reduced number of intrusion errors and verbal paraphasias in naming and immediate serial recall tasks was further noticed. At the neural level, following training, CT showed increased activity in fronto-temporal areas associated with phonological processing and control, as compared to controls. These results highlight the specificity of treatment programs of verbal inhibition, and by extension, of verbal language control by distinguishing between phonological and semantic inhibitory processes.