| dc.description.abstract | Aphasia is an acquired communication disorder resulting from damage to language regions of the brain. Speech-language pathologists frequently use rhythmic elements (e.g., tapping to a beat) to facilitate speech output in individuals with aphasia; however, there is very little empirical work on rhythm in aphasia at both a neural and a behavioral level. Even further, there is a need for a comprehensive understanding of the brain regions involved in musical rhythm in a neurotypical population – a requisite for understanding what happens to this network following brain injury. This dissertation begins to address these critical gaps through two main aims to: 1) identify a brain network for musical rhythm in neurotypical adults (Chapter 2) and 2) characterize rhythm abilities, and their relationship to lesion location and language profiles, in individuals with post-stroke aphasia using an individual differences approach (Chapter 3). To achieve the first aim, I conducted a systematic review and meta-analysis of 30 functional magnetic resonance imaging (fMRI) studies of musical rhythm. I found that rhythm is largely represented in a bilateral cortico-subcortical network. To achieve the second aim, a cohort of 33 individuals with chronic, post-stroke aphasia and a comparison group of 29 neurotypical controls completed a battery of rhythm production and perception tasks. Most individuals with aphasia performed within the normal control range, but about one-third did not. Using lesion-symptom mapping, I found that those who struggled with tapping tended to have damage to a left posterior perisylvian region at the crux of the temporal and parietal lobes; this area has been implicated in auditory-motor transformations such as phonological encoding. Additionally, rhythm abilities correlated with overall aphasia severity but not with motor speech. In Chapter 4, I present new ideas and future clinical directions for individualizing aphasia treatment strategies, connecting the present findings with literature on rhythm-based therapies for aphasia. This dissertation provides new, clinically-translational knowledge on how beat synchronization – a basic human capacity – is represented in the brain. | |
