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Sharaine J. Rawlinson, MSW
Western Region Outreach Center & Consortia (WROCC)
National Center on Deafness
California State University Northridge
18111 Nordhoff Street
Northridge, CA 91330-8267
Phone: (505)-275-6872 Voice/TTY/Fax
Cochlear implants have long been investigated and designed, starting back in the 1700's. It's only been since 1975 that implants have been approved for research by the US Food and Drug Administration. Originally only approved for implantation in adults, cochlear implants are now approved for children from the age of 12 months and older.
How Cochlear Implants Work.
Hearing takes place when sound is received through the outer ear, into the middle ear where the eardrum conducts sound to the inner ear. Once inside the inner ear, three bones conduct the sound which is then sent to the cochlea. The cochlea is comprised of small hairs called cilia. For many people with nerve deafness, the cilia no longer work due to the cochlea's integrity being compromised.
Cochlear implants are designed to by-pass cochlear hair cells which are non-functioning and provide direct stimulation to the auditory nerve. Thus, the internal device is implanted with the electrode array into the cochlea, enabling the individual electrodes to stimulate the nerve directly, mimicking sounds at various frequencies along the cochlea, resulting in the transmission of codes which the brain must decipher.
Specifically, the microphone picks up sounds and sends them to the processor. The processor then selects and codes sounds which produce useful speech, music, etc. From the processor, sounds are transmitted through the skin to the receiver/stimulator via the magnetic headset. From here, the codes are then converted to electrical signals which activate the electrode arrays. The electrodes then stimulate the auditory nerve where the brain recognizes the electrical signals as sounds.
This is a Nucleus 24* Receiver/Decoder/Stimulator with the two electrode arrays.
This is an example of the external components of cochlear implants. Shown is the body processor and behind the ear for the Nucleus 24.
Cochlear Implants and Assistive Listening Devices.
In spite of the exemplary technology that science has presented in the form of audiological bionics, cochlear implants alone are not always sufficient to deliver sound to the implantee. For example, dining in a restaurant is most often a challenge to the cochlear implant user because of the extraneous noise levels. In such a situation, the desire to take advantage of other technology is realized. Specifically, assistive listening devices (ALDs) work in tandem along side cochlear implants in much the same fashion as they work with hearing aids. Below, the authors offer some suggestions and images of how ALDs can be connected to cochlear implants.
Shown are the author's two cochlear implant processors: to the left is the body-worn processor (BWP) and to the right is the behind the ear (BTE) processor. Both processors have jacks to which assistive listening technology can be connected.
This photo shows a body-worn processor (Nucleus 24 Sprint) connected to a Williams Sound PockeTalker. Cochlear Corporation does make available a lapel microphone that can be plugged directly into the processor for use in one-on-one situations. The author likes to use hers, for example, when driving in a car. The microphone picks up a speaker's voice and sends the sound clearly without much of the engine and road noise that is present in the automobile.
For individuals who do not have the lapel microphone, a PockeTalker would be ideal. Note the microphone on the PockeTalker. This is used in one-to-one situations where a cochlear implantee wants to understand a speaker in an intimate setting but in which there is extraneous noise. The speaker uses the microphone on the PockeTalker which is connected to the BWP processor via a patch cord. When the speaker talks into the microphone, sound is automatically directed through the processor and into the cochlear implant, giving the implantee access to direct sound without extraneous noise interference.
This image shows a BTE processor with an adapter cable, a patch cord, and the Williams Sound PockeTalker. In this situation, because a patch cable is needed and the end of the cable is too large for the jack at the bottom of the BTE, an adapter cable is also required. The adapter cable plugs into the end of the BTE, then the patch cord plus into the adapter at one end and into the PockeTalker at the other end. Again, this is good for situations which are small and commentary is only between the implantee and one or two other people.
These two photos show how a Williams Sound Tele-Link can be connected to a BWP processor, thus enabling a cochlear implant user to speak directly into the telephone receiver while receiving sound directly into their cochlear implant via the Tele-Link. Again, this reduces the sound from outside sources and improves the quality of sound being transmitted to the implantee.
It should be noted that some cochlear implants are now being manufactured with built-in telecoils. In these situations, a cochlear implantee can simply turn on their telecoil and be able to hear more clearly on the telephone.
These two photos above show a telecoil connected to the Nucleus 24 BTE processor. In the photo on the left, there is simply the telecoil connected to the BTE. On the right, the telecoil is shown alongside a personal FM system. If an implantee has a patch cord, they can simply plug one end of the patch cord into the FM system and the other end into the processor.
In the cast of an implantee not having a patch cord, the person can plug the telecoil into the BTE and attach it to their lapel. At the same time, they can put an FM neck loop on around their neck which works in tandem with the telecoil to induct the sound from a speaker's microphone. This system also works with the BWP processor.
A personal FM system is ideal in a conference setting where the speaker's microphone is connected to an FM transmitter. The personal FM receiver then receives the sound signal and then the telecoil, in turn, transmits the sound directly to the cochlear implant processor. As with all ALD systems, the personal FM system works to eliminate extraneous noise, allowing the cochlear implant user to listen to the same information as individuals with normal hearing who can "tune out" extraneous noise.
With the continuous improvement in bionics, especially cochlear implant technology, more and more people are turning to implants as a means of addressing their hearing loss. Although the bionic ear technology is far better than even 20 years ago, it still cannot mimic exactly the function of a normal ear and brain functions. Therefore, the ability to tap into assistive listening devices to augment cochlear implant use is paramount. As more implantees become aware of ALDs and the capabilities they offer, manufacturers are attending to this heightened level of awareness and striving to develop assistive listening devices which work seamlessly along with CIs.
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