Exploring the brain basis of rhythm in individuals with aphasia

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PROJECT SUMMARY The goal of this proposal is to characterize the neural substrates underlying rhythm abilities and the relationship with language profiles in individuals with aphasia. Aphasia is an acquired communication disorder resulting from damage to language regions of the brain, with stroke as the leading cause. Currently, over 2 million individuals in the United States are living with aphasia. Aphasia is notoriously difficult to treat and patients exhibit significant individual variability in recovery trajectories and in what therapeutic elements work best in aiding such recovery. Speech-language pathologists frequently use rhythmic elements (e.g., tapping to a beat) in the clinic in order to facilitate speech output. However, there is a lack of a deep and systematic empirical assessment of rhythm in aphasia at both a behavioral and neural level. Our first aim is to characterize the neural basis of individual differences in rhythm abilities in individuals with chronic, post-stroke aphasia. To do this, we will administer a comprehensive battery of rhythm perception and production tasks to a large cohort of individuals with aphasia and age-matched controls. We will then employ multivariate lesion-symptom mapping, a machine-learning methodology for identifying brain-behavior relationships, to determine which brain regions are associated with rhythm processing in aphasia. We hypothesize that individuals who have damage to brain regions important for rhythm, including the basal ganglia or the left inferior frontal gyrus (LIFG), will exhibit the greatest impairments in rhythm. Critically, the LIFG is a core language region typically damaged in post-stroke, non-fluent aphasia. Motivated by robust evidence for associations between rhythm and language across cognitive, neural, and behavioral domains, we will assess the relationship between rhythm and language measures in aphasia in our second aim. We predict that individuals with higher rhythm abilities will have higher language scores, particularly on measures of connected speech. This mentored training award will provide the applicant with training in advanced neural and behavioral data analysis techniques and expertise in large-scale project management with a patient cohort. With significant and timely clinical relevance, our proposal will address vital gaps in the literature by taking an individual differences approach to understanding the relationship between rhythm, the brain, and language in aphasia.