What is a cochlear implant (CI)?

Cochlear implants are small, electronic devices that provide awareness and understanding of sound to those suffering from severe hearing loss. The devices are used for those who do not benefit from the use of hearing aids. Cochlear implants are different from hearing aids because while hearing aids amplify and reintroduce the sound signal to the ear, implants bypass the ear structures completely.

In a normal listener, sound energy is used to stimulate the hearing nerve. Electrical contacts placed within the cochlea (the auditory portion of your inner ear) send signals to the hearing nerve. These signals form a code based on those features of speech that are critical to understanding words. The brain is capable of interpreting this "code" to enable speech understanding and appreciation of the surrounding soundscape.

Cochlear implants aim to mimic this system.

The term "cochlear implant" actually refers to a system of technologies that processes and transmits information. The system has four components:

• External microphone - picks up sound from the environment.
• External speech processor (a computer) - translates the sound energy picked up by the microphone into a code that the brain can understand. The processor is worn either behind the ear or on a belt.
• External transmitter - sends coded information that is based in sound to the internal receiver/stimulator. It is magnetically attached and worn behind the ear and under the hair.
• Internal receiver/stimulator - receives the coded information. It is about the size of a quarter and is placed under the scalp, behind the ear.

Wire circuits threaded into the cochlea transmit the sound information from the internal receiver to the inner ear. Signals transmitted down the wire stimulate the nerves inside the cochlea, creating a train of impulses conveyed to the brain to produce what we call "sound."