Assessing the Efficacy of Implicit Training for Verb Tense Deficits in Aphasia: A Proof-of-Concept Single Subject Experimental Design

Abstract

Aphasia is a language disorder caused by acquired brain damage that affects language production and comprehension. Agrammatic aphasia is characterized by reduced sentence complexity, frequent grammatical errors, particularly on verb inflections. Existing verb inflection treatments rely on explicit learning methods, involving intensive feedback on grammar rules, which may place high demands on cognitive processes such as working memory. Alternatively, individuals with aphasia can learn through implicit exposure to syntactic structure without reliance on explicit memory or conscious awareness. The current study investigated whether a novel implicit sentence priming treatment could improve verb inflection deficits in individuals with agrammatic aphasia. Generalization to untrained tenses (present and future) and verbs (regular and irregular) was also examined, and outcomes were compared to morphosemantic treatment, a well-established explicit intervention. Using a single-subject design, two participants with impaired verb tense production were trained on regular past tense verbs using implicit priming. Post-treatment results showed significant improvement on trained items for one participant, and the second participant showed partial improvement by increasing the production of verb+ed verbs and subject-verb-object structure, but continued to make grammatical errors. Generalization to untrained verbs and tenses was limited. These findings provide preliminary evidence that implicit priming may support trained verb tense production in some individuals with agrammatic aphasia, while highlighting the need for replication and direct comparisons with explicit treatments with larger, more diverse samples.