Remapping of the somatosensory cortex after a photothrombotic stroke: dynamics of the compensatory reorganization.

Although stroke can affect cerebral structure and function, the brain has a potential for plasticity thanks to which some degree of function can be restored. The pathways of such recovery are of great interest, since the dynamics of rewiring of the injured brain may become the basis for designing appropriate strategies of rehabilitation. We investigated the spontaneous plasticity of cortical somatosensory representations following a focal unilateral stroke in the barrel cortex of rats. Ischemic lesions were produced with the photothrombotic technique in the cortical representation of vibrissae. Functional activation of the brain in response to the stimulation of vibrissae with destroyed cortical representation was monitored through the 2 months post-stroke survival period with [(14)C] 2-deoxyglucose (2DG) autoradiographic brain mapping (1, 7, 28, 56 days after the stroke). 2DG uptake was measured on autoradiograms of tangential sections in several regions of somatosensory cortex and in motor, auditory and prefrontal cortex. Behavioral deficit was assessed by the gap-crossing test 3, 28, 56 days after the stroke. Changes in the activation pattern of the intact hemisphere and non-vibrissal somatosensory representations of the lesioned hemisphere evolved during the observation period. Full recovery of the behavioral function was reached 2 months after the stroke and at the same time, new foci of activation were observed in the lesioned hemisphere. At that time, hyperactivation of the somatosensory areas in the intact hemisphere subsided. The new activation foci located in representations of anterior vibrissae, front paw and hind paw were specific for the vibrissae stimulation and were most probably a new functional representation of the vibrissae. We demonstrated spatial and temporal remodeling of the brain induced by cortical stroke, leading to vicariation of function.