Neural interface systems are becoming increasingly more feasible for brain repair strategies. This paper tests the hypothesis that recovery after brain injury can be facilitated by a neural prosthesis serving as a communication link between distant locations in the cerebral cortex. The primary motor area in the cerebral cortex was injured in a rat model of focal brain injury, disrupting communication between motor and somatosensory areas and resulting in impaired reaching and grasping abilities. After implantation of microelectrodes in cerebral cortex, a neural prosthesis discriminated action potentials (spikes) in premotor cortex that triggered electrical stimulation in somatosensory cortex continuously over subsequent weeks. Within 1 wk, while receiving spike-triggered stimulation, rats showed substantially improved reaching and grasping functions that were indistinguishable from prelesion levels by 2 wk. Post hoc analysis of the spikes evoked by the stimulation provides compelling evidence that the neural prosthesis enhanced functional connectivity between the two target areas. This proofof-concept study demonstrates that neural interface systems can be used effectively to bridge damaged neural pathways functionally and promote recovery after brain injury.brain-machine-brain interface | neural plasticity | traumatic brain injury | closed-loop | long-term potentiation T he view of the brain as a collection of independent anatomical modules, each with discrete functions, is currently undergoing radical change. New evidence from neurophysiological and neuroanatomical experiments in animals, as well as neuroimaging studies in humans, now suggests that normal brain function can be best appreciated in the context of the complex arrangements of functional and structural interconnections among brain areas. Although mechanistic details are still under refinement, synchronous discharge of neurons in widespread areas of the cerebral cortex appears to be an emergent property of neuronal networks that functionally couple remote locations (1). It is now recognized that not only are discrete regions of the brain damaged in injury or disease but, perhaps more importantly, the interconnections among uninjured areas are disrupted, potentially leading to many of the functional impairments that persist after brain injury (2). Likewise, plasticity of brain interconnections may partially underlie recovery of function after injury (3).Technological efforts to restore brain function after injury have focused primarily on modulating the excitability of focal regions in uninjured parts of the brain (4). Purportedly, increasing the excitability of neurons involved in adaptive plasticity expands the neural substrate potentially involved in functional recovery. However, no methods are yet available to alter the functional connectivity between spared brain regions directly, with the intent to restore normal communication patterns. The present paper tests the hypothesis that an artificial communication link between uninjured regions of the...