MEG of Somatosensory & Attentional Processes

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The objective of this proposal is to address the question of how changes in cortical activity that follow ischemic insult are related to functional improvement of somatosensory and attentional processes. In order to meet this objective, we will specify the parameters of cerebral reorganization underlying recovery of somatosensory and attentional functions in patients with unilateral ischemic stroke using magnetoencephalography (MEG). We will then determine the correspondence between MEG parameters of reorganization and relevant behavioral measures of recovery of function. In addition, we will outline the relation between stroke lesion variables (volume and location) and MEG-based indices of reorganization, as well as between lesion variables and behavioral measures of functional recovery. An understanding of cortical mechanisms of recovery and reorganization will help determine prognosis and optimal treatment for individuals recovering from somatosensory and attentional deficits following cortical infarction. The study design includes a baseline behavioral and neuropsychological assessment followed by MEG and MRI imaging at 2-3 months and 10-12 months post-stroke. We will obtain spatiotemporal MEG maps of brain activity associated with stimulation of the fingertips of both hands in patients with current or prior hemianesthesia at these two time intervals. A subset of these patients will have undergone constraint-induced therapy (CIT) and will be compared with control participants who have been treated with standard care therapy. We will also obtain spatiotemporal maps of cortical activity associated with selective attention to visual stimuli in patients recovering or recovered from unilateral neglect (with or without hemianesthesia) over the same time interval. Changes in MEG parameters (anatomical location, magnitude, and time course of the event-related magnetic response) will establish the nature and extent of reorganization in relation to behavioral and cognitive recovery. The relations between these parameters and detailed volumetric analyses of structural MRIs obtained at the same time periods will reveal associations between stroke type and cortical reorganization related to recovery.