People are using brain-machine interfaces to restore motor function in ways never before possible - through limb prosthetics and exoskletons. Technologies to repair cognition have been more elusive. That's rapidly changing with tools -- from fully implantable brain devices to neuron-eavesdropping grids atop the brain -- to directly probe the mind. These technologies are mapping new understandings of cognition and advancing efforts to improve memory in patients with cognitive deficits.