Asymmetry of hemispheric interdependences in the early hours following unilateral stroke: An electrophysiological study in rats.

Disturbance of interhemispheric interactions after stroke has been widely reported. However, the dynamic change in the hyperacute stage of stroke remains to be elucidated. In this study, interhemispheric interactions and brain asymmetry in the early hours after infarction were investigated in animals from the aspect of nonlinear interdependences using bilateral EEG recordings. Both the right-to-left and the left-to-right hemispheric interdependences were impaired after unilateral stroke, with a significant decrease in the first two hours and a low level in the following twenty-two hours. The ipsilesional to contralesional interdependence was found more vulnerable to unilateral stroke, and the symmetry between the right-to-left and the left-to-right hemispheric interdependences was damaged. The brain symmetry index after four hours was significantly correlated with the infarct volume at twenty-four hours, suggesting its prognostic role as early as four hours post-stroke.