A cochlear implant is an electronic prosthetic replacement for damaged cells in the inner ear. It is made up of two parts. The implanted part includes an electronic circuit surgically placed in the skull behind the ear (on the mastoid process of the temporal bone). This circuit is attached to a bundle of tiny wires that are inserted into the cochlea. At the end of the wires are as many as 24 electrodes that cover a distance of 25 mm along the length of the cochlea. Stimulation of each electrode usually causes a different pitch percept.The other part of the device is external and has a microphone, a speech processor, and connecting cables.There are several different manufacturers of implants, but this is a good example:
Sounds are picked up by the small, directional microphone located in the headset of the ear (1). The microphone picks up all sound from the environment whether it is speech, environmental sounds or music.
A thin cord (2) carries the sound from the microphone to the speech processor, a powerful miniaturized computer (3), which you wear in a pocket or on your belt.
The speech processor filters, analyzes and digitizes the sound into coded signals (3)
The coded signals are sent from the speech processor via a cord (4) to the transmitting coil (5)
The transmitting coil sends the coded signal as FM radio signals to the cochlear implant under the skin (6).
The cochlear implant sends ths electrical energy to the electrodes which have been inserted into the cochlea to stimulate the nerve fibers (7).
The resulting electrical sound is sent to the brain for processing (8). Although the process seems complicated, the sound is transmitted in microseconds, so there is no delay between what the person hears and what his or her brain processes.
State-of-the art cochlear implant devices now have up to 24 electrodes which stimulate the hearing nerves. These multichannel implants have the advantage of stimulating many places along the nerve thereby transmitting more detailed information to the brain. The more information that reaches the brain, the greater the patient's ability to understand what is happening in his/her environment.
Is this a new technique?
The cochlear implant was invented about twenty five years ago to help severely to profoundly deaf persons communicate more easily. Thanks to extensive research and evolving technology the device has come to be accepted as a most valuable one for persons with this much hearing loss. Cochlear implants are recognized by the American Medical Association (AMA) and the American Academy of Otolaryngology - Head and Neck Surgery (AAO- HNS) as an approved medical procedure for adults and children. They were approved by the Food and Drug Administration (FDA) in the mid-1980s and are covered by insurance policies, Medicare, Medicaid and Vocational Rehabilitation. There are now more than 60,000 individuals worldwide who have received cochlear implants.
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