Stroke and Neurodegeneration Induce Different Connectivity Aberrations in the Insula.

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Stroke and neurodegeneration cause significant brain damage and cognitive impairment, especially if the insular cortex is compromised. This study explores for the first time whether these 2 causes differentially alter connectivity patterns in the insular cortex. Resting state-functional magnetic resonance imaging data were collected from patients with insular stroke, patients with behavioral variant frontotemporal dementia, and healthy controls. Data from the 3 groups were assessed through a correlation function analysis. Specifically, we compared decreases in connectivity as a function of voxel Euclidean distance within the insular cortex. Relative to controls, patients with stroke showed faster connectivity decays as a function of distance (hypoconnectivity). In contrast, the behavioral variant frontotemporal dementia group exhibited significant hyperconnectivity between neighboring voxels. Both patient groups evinced global hypoconnectivity. No between-group differences were observed in a volumetrically and functionally comparable region without ischemia or neurodegeneration. Functional insular cortex connectivity is affected differently by cerebral ischemia and neurodegeneration, possibly because of differences in the cause-specific pathophysiological mechanisms of each disease. These findings have important clinical and theoretical implications.