Neuroprosthetics are implantable devices designed to replace or improve the function of a certain aspect of the central nervous system. The most famous and widely-used neuroprosthetic is the cochlear implant, which bypasses the eardrum and directly stimulates the human auditory nerve, giving the power of hearing to those who lack it. The first cochlear implant was built in 1957, and today, these implants are used by over 100,000 people.
There are three main types of neuroprosthetics - sensory prosthetics, motor prosthetics, and cognitive prosthetics. Sensory prosthetics get information into sensory areas like hearing and sight, motor prosthetics help regulate or stimulate malfunctioning motor functions, and cognitive prosthetics are a largely still-on-the-drawing board field of future prosthetics for replacing or improving problem areas in the brain itself. Although the term "neuro" makes us think of the brain, all neuroprosthetics in use today replace nervous system aspects external to the brain.
Research in visual neuroprosthetics has given rise to extremely fine electrodes, thinner than a human hair. This has helped progress tangential areas of neurophysiology, but unfortunately true visual prostheses - devices which would allow the blind to see - are still in development. Scientists have observed that selective stimulation of the visual cortex allows subjects to see phosphenes - the little glowing blurs you see when you rub your eyes - in pre-determined areas of the visual field. Research has produced visual prostheses that give patients fuzzy vision with a pixel resolution of about 20 x 20, but these are just experimental and not ready for mass use.
In the area of motor neuroprosthetics, there is the well-known pacemaker, which stimulates the heart to beat when the natural cluster of pacemaker cells is having problems. Bladder control neuroprosthetics have helped patients with paraplegia due to spinal cord damage. Motor neuroprosthetics for the conscious control of movement have gotten some press in recent years. Patients who are totally paralyzed can be given these implants, which allow them to control a computer mouse for spelling out messages, playing games, or surfing the web. For someone who is otherwise locked in an unresponsive body, these implants can radically improve quality of life.
Research into neuroprosthetics is an ongoing and cutting-edge area of science. We should expect to see many more developments in the future, some of which will challenge common assumptions about the interface between the mind and machines.
