Dynamic stimulation of visual cortex produces form vision in sighted and blind humans

A visual cortical prosthesis(VCP) has long been proposed as astrategy for restoringuseful vision to the blind, under the assumptionthat visual percepts of small spots of lightproduced withelectrical stimulation of visual cortex (phosphenes) will combine into coherent percepts of visual forms, like pixels on a video screen.We tested analternative strategy in which shapes were traced on the surface of visual cortex by stimulating electrodes in dynamic sequence. In both sighted and blind participants, dynamic stimulation enabled accurate recognition of letter shapespredicted by the brain’s spatial map ofthe visual world.Forms could be presented and recognized rapidlyby blind participants, up to 86 forms per minute.These findings demonstrate that a brainprosthetic can produce coherent perceptsof visualforms.