Functional reorganization of the reading system following stroke

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Project Summary/Abstract Many survivors of a left-hemisphere stroke are impaired at reading, at least immediately following the stroke. Reading impairments have a profound impact on one's well being. Reading typically improves over years following the stroke, though some degree of impairment remains common. Improvements in reading during recovery are thought to depend on neural plasticity, or the damaged brain reorganizing to better support the impaired reading functions. The long-term objective of our research is to characterize this neural plasticity so that we can develop new interventions that will enhance the recovery of reading following stroke. The immediate goal is to map this neural plasticity using functional neuroimaging, comparing a group of patients with reading impairments following stroke to controls, with the following three aims. Aim 1: We will investigate the extent to which there are consistent patterns of activation during reading tasks that distinguish individuals with reading impairments following stroke from control participants. Aim 2: We will use functional magnetic resonance imaging (fMRI) decoding methods to determine whether patients and controls differ in what different parts of the brain are doing functionally. Neural plasticity has been argued to either reflect functional take-over, whereby the function previously performed by a damaged area is shifted to a different brain region, or reflect a compensatory masquerade, i.e., the refinement of an intact cognitive process not normally used to perform a task. To determine which type of neural plasticity is occurring in the reading network, new fMRI analysis techniques are needed that go beyond activity magnitude investigations of brain regions to decode the information present in the distributed patterns of activation. We will develop such techniques and apply them to our sample to determine the extent to which individuals with chronic reading problems show consistent types of neural plasticity. Aim 3: Increases in neuronal activation to language tasks are often observed in unexpected regions with brain damaged participants. Little is known about what function these regions serve for patients during their recovery. Using the methods developed in Aim 2, we will investigate the function of these additional activated regions in our sample. The proposed research will make progress towards characterizing the nature of neural plasticity in the reading system following stroke, including an innovative approach for investigating what shifts in the neuronal activation profile of patients means in terms of changes in cognitive function. This research will provide key preliminary data to support a R01 grant application that will further elucidate how patterns of neural plasticity might differ among participants depending on lesion location or behavioral impairment, mapping these changes longitudinally across the acute through chronic phases of stroke and delineating neural plasticity in response to specific treatments. The proposed project builds on the PI's solid track record of research in cognitive theories of reading, investigations of individuals with acquired written language impairments, and use of innovative, theoretically grounded analysis tools for fMRI data.