Cellular-resolution monitoring of ischemic stroke pathologies in the rat cortex

Stroke is a leading cause of disability in the Western world. Current post-stroke rehabilitation treatments are only effective in approximately half of the patients. Therefore, there is a pressing clinical need for developing new rehabilitation approaches for enhancing the recovery process, which requires the use of appropriate animal models. Here we study the activity patterns of multiple cortical regions in the rat brain using two-photon microscopy. We longitudinally recorded the fluorescence signal from thousands of neurons labeled with a genetically-encoded calcium indicator before and after an ischemic stroke injury, and found substantial functional changes across motor, somatosensory, and visual cortical regions during the post-stroke cortical reorganization period. We show that a stroke injury in the primary motor cortex has an effect on the activity patterns of neurons not only in the motor and somatosensory cortices, but also in the more distant visual cortex, and that these changes include modified firing rates and kinetics of neuronal activity patterns in response to a sensory stimulus. Changes in neuronal population activity provided animal-specific, circuit-level information on the poststroke cortical reorganization process, which may be essential for evaluating the efficacy of new approaches for enhancing the recovery process.