The proposed research represents a coordinated interdisciplinary study of brain injury. The objective is to develop a comprehensive understanding of the complex of responses of brain to different types of trauma. Three types of unilateral injury will be compared: a partial undercut of cortex as a model of laceration; an impact injury to that area as a model of contusion and subcortical electrolytic lesions of the substantia nigra. The lesions will be standardized in rats and cats and behavioral impairment and recovery of functions tested with objective methods. Parallel studies of these standardized lesions' spatial extent and charges over time will be conducted using light and electron microscopy, histochemistry and electrophysiology.