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How Does a Cochlear Implant Work?
A cochlear implant is very different from a hearing aid. Hearing aids amplify sounds so they may be detected by damaged ears. On the other hand, cochlear implants bypass damaged portions of the ear and directly stimulate the auditory nerve. Signals generated by the implant are sent by way of the auditory nerve to the brain, which recognizes the signals as sound. A cochlear implant allows many people to recognize warning signals, understand other sounds in the environment, and enjoy a conversation in person or by telephone. Each implant system consists of two parts; an internal component and an external component.
The internal component consists of a decoder and magnet housed in protective casing. The electrode array extends from this casing. The surgeon will drill into the skull to make a "bed" for the decoder. The remainder of the internal component sits on the skull but under the skin. The magnet picks up the information provided from the external components. The internal component then determines which electrodes will fire with what power/current.
The external components consist of a microphone, a series of cords, a transmitting coil and a speech processor. Each part must be worn in order for the device to work. The microphone picks up sounds preferentially from the front of the listener and transmits the sound along the long cord to the speech processor. The speech processor contains a program individual to each listener indicating the minimum amount of current needed for a sensation of first hearing and the maximum amount of current tolerable. This program extracts the most important aspects of the incoming speech signal and transmits this information back up the long cord across to the transmitting coil. The signal travels across the skin via radio frequencies to the internal component. The decoder of the internal component takes this information and determines which electrodes will fire and with what power. This processing of sound takes place in real time.
How Does Someone Receive a Cochlear Implant?
Criteria for candidacy continues to change as technology and surgical procedures advance. Use of a cochlear implant requires both a surgical procedure and substantial therapy to learn or relearn the sense of hearing.
Factors which may affect outcomes include: duration of hearing loss, amount of residual hearing, age of identification and intervention, age at implantation, status of the cochlea/cochlear nerve as well as other medical conditions.
While the technology now available for people who are deaf and hard of hearing is already quite effective, it continues to improve all the time. Major advances are continually being made, so that children with severe to profound hearing losses can now have access to sound which can be used for effective development of oral language. An implant does not restore normal hearing. Instead, it can give a deaf person a useful representation of sounds in the environment and help him or her to understand speech.
By: Kimberly Powell |
