Functional Connectivity Correlates of Subacute to Early Chronic Post-Stroke Aphasia Recovery

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Project Summary Aphasia, an acquired language disorder, is a common post-stroke condition that devastates patients’ ability to engage in social situations, participate in preferred activities, and often regain a high quality of life after a stroke. Aphasia recovery is often greatest during the subacute post-stroke phase (~ 2 weeks to 6 months post- stroke) due to neuroplasticity (i.e., reorganization of brain function and behavior relationships). Yet, the extent of subacute aphasia recovery varies widely between individuals, and current predictive models based on demographic and lesion data do not fully account for inter-individual variability in recovery. Early post-stroke recovery predictions are likely to improve with the inclusion of information about brain network function, yet very little is currently known about the functional connectivity correlates of language changes that occur over the subacute phase in people with aphasia (PWA). This research aims to address this gap. Twenty-five PWA in the subacute phase (£ 3 months post-stroke onset at study entry) and 25 neurotypical controls will participate in the proposed research. At study entry, all participants will complete language testing, resting-state functional Near- Infrared Spectroscopy (rs-fNIRS), and structural MRI. PWA will complete testing and rs-fNIRS again at the onset of the early chronic phase (~ 6-8 months post-stroke). fNIRS will be used in this research to index brain network function as it is a flexible, portable alternative to fMRI that is more accessible to patients in early post-stroke stages. Language impairments will be captured by measures of semantics and phonology, linguistic domains that underlie receptive and expressive language deficits in PWA and provide more specific information than global language measures regarding impairment locus. Through three study aims, we will determine the subacute rs-fNIRS functional connectivity patterns that (1) are associated with subacute language deficits, (2) change over time and are related to longitudinal language changes, and (3) predict language gains by the early chronic stroke stage. Across aims, we predict that stronger/increased left intra- and inter-hemispheric connectivity will be associated with better/improved language skills in PWA, consistent with prior subacute stroke fMRI work. We additionally hypothesize that relationships between functional connectivity and language will be spatially localized to ventral stream regions for semantics and dorsal stream regions for phonology, consistent with modern models of the neurobiology of language. By achieving these aims, this project will advance our understanding of the nature of beneficial neural reorganization of language during the crucial subacute to early chronic post-stroke recovery window. This line of work will provide a foundation for building computational recovery models that incorporate multimodal brain function and brain structure data in PWA. Integration of these types of data will also guide decisions regarding the timing and type of language and non-invasive brain stimulation therapies patients should receive to maximize their recovery during the subacute stroke phase.