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Neural prosthetics (also called neuroprosthetics) is a discipline related to neuroscience and biomedical engineering concerned with developing neural prostheses. Neural prostheses are a series of devices that can substitute a motor, sensory or cognitive modality that might have been damaged as a result of an injury or a disease. An example of such a device is the cochlear implants. This device substitutes the functions performed by the ear drum, frequency analysis in the cochlea, and instead stimulates the auditory nerves directly. A microphone on an external unit gathers the sound and processes it, the processed signal is then transferred to an implanted unit that stimulates the auditory nerves through a microelectrode array. The development of such devices has had a profound impact on the quality of human life. The research in this field is intended to resolve disabilities, but as such an unproductive distinction is drawn between therapy and enhancement.
Neuroprosthetics present many biomedical engineering challenges. Any implanted device has to be very small in order to be to minimally invasive, especially in the brain, eye, cochlea. The implant has to communicate with the outside world wirelessly. Having wires sticking out of the head, eye, etc. is not an option. Besides the discomfort and restrictions it would impose on the subject this could lead to infection in the tissue. This bidirectional wireless communication requires a high bandwidth for real-time data transmission; this is a significant challenge given that the data link has to operate through the skin. The minimal size of the implant means a battery cannot be embedded in it, and instead the implant works on wireless power transmission through the skin which presents data transmission challenges. The tissue surrounding the implant is usually very sensitive to temperature rise, so the implant must have minimal power consumption so as to avoid damaging the tissue. Another very important issue is the bio-compatibility of the material that the implants are coated with. The more bio-compatible the materials are the less likely they are to cause a reaction or infection in the tissue.
As these devices become safer and our understanding of how the brain works grows, the use of these devices they will become increasingly commonplace. The neuroprosthetic with the most widespread use is the cochlear implant, with approximately 100,000 in use worldwide as of 2006.
Categories of neural prosthetics include visual prosthetics, auditory prosthetics, prosthetics for pain relief, motor prosthetics, bladder control implants, motor prosthetics for conscious control of movement (Brain-computer interfaces), motor prosthetics, and even cognitive prosthetics to mimic a brain region such as the hippocampus.
The use of cochlear implants and pacemakers has become an accepted part of life. The future holds exciting prospects for the everyday use of a variety of more advanced neural prostheses.