Video display for the tongue

The BrainPort is a visual prosthetic for the blind that converts images from a video camera into tactile sensations on the tongue. It was first developed at the University of Wisconsin in a research group led by the late Paul Bach-y-Rita, the "father" of approaches to substitute one sense for another. The technology has been spun out for commercialization but is not yet FDA approved. During trials, blind test subjects had their brains scanned while using the device. Interestingly, even though the device provides tactile sensation, visual regions of the brain were activated. From the BrainPort description:

The BrainPort vision system consists of a postage-stamp-size electrode array for the top surface of the tongue (the tongue array), a base unit, a digital video camera, and a hand-held controller for zoom and contrast inversion. Visual information is collected from the user-adjustable head-mounted camera (FOV range 3–90 degrees) and sent to the BrainPort base unit. The base unit translates the visual information into an stimulation pattern that is displayed on the tongue.  The tactile image is created by presenting white pixels from the camera as strong stimulation, black pixels as no stimulation, and gray levels as medium levels of stimulation, with the ability to invert contrast when appropriate.  Users often report the sensation as pictures that are painted on the tongue with Champagne bubbles.

With the current system (arrays containing 100 to 600+ electrodes), study participants have been able to recognize high-contrast objects, their location, movement, and some aspects of perspective and depth. Trained blind participants use information from the tongue display to augment understanding of the environment. Our ongoing research with the BrainPort vision device demonstrates the great potential of tactile vision augmentation