PROJECT SUMMARY Among the 795 000 Americans who have a stroke each year, about 84 000 experience chronic aphasia?an impairment of language production, and often to a lesser extent, comprehension, that can severely impact the quality of life for people living with aphasia and their family members. Research has shown that people with chronic aphasia can benefit from treatment, but significant communication challenges often persist beyond conclusion of therapy. This project aims to test and develop a promising treatment technique, termed speech entrainment, to enhance treatment outcomes for people with aphasia. Speech entrainment refers to speaking in unison with a model speaker by imitating the model in real time. Research has shown that speech entrainment is a ground-breaking technique for prompting connected speech in people with aphasia. Even those whose independent speech is limited to a few single words may be able to increase their speech output many-fold in a speech entrainment context. This immediate stimulation effect is well-documented. What remains poorly understood is whether practicing speech production along with an entrainment model will enhance independent speech at a later point in time when the entrainment support is removed. In addition, conditions that optimize outcomes and characteristics of those who benefit have not been investigated beyond the immediate stimulation. Thus, this project aims to (1) experimentally establish the direct effect of speech entrainment practice on independent speech production post-treatment, (2) identify conditions that enhance treatment benefits, and (3) define the cognitive-linguistic and neuroanatomic profiles that are associated with a positive treatment response. These aims are addressed in a within-subject efficacy study, where 40 people with aphasia produce different stories with entrainment support. Speaking without entrainment is evaluated one day before and one day after speech entrainment practice. Different practice stories will be randomized within participants to three experimental conditions to assess the effect of treatment (trained vs. untrained), training schedule (massed vs. distributed presentation of stories), and entrainment modality (practice with auditory-only or audiovisual model). Correct information units per minute for each story will be tallied to evaluate the differences between conditions and the associations with patient characteristics. For consistency with prior research, number of different words per minute will serve as a secondary outcome. The proposed research addresses a clinical need by testing and optimizing a promising treatment technique for enhancing aphasia rehabilitation. In addition, this study serves as pilot research for a subsequent R01 grant. Guided by the findings from this study, the subsequent clinical trial establishes the efficacy of speech entrainment practice in a full-scaled treatment study, implemented at intensities that are designed to test long-term benefits.