How a Cochlear Implant Works

All cochlear implants consist of two general components: the internal device (e) and the external hardware (a-d). The internal portion of the implant consists of two parts: the receiver/stimulator and the intracochlear electrode array. The external portion consists of three parts: a microphone, a speech processor, and a transmitting coil.

Cochlear Implant Diagram

Sound is picked up by the microphone (a), where it is sent down a cord (b) to the speech processor (c). The speech processor filters the incoming acoustic signal into separate frequency bands, and then converts this information into digital form. The digitized signal is sent back up the cord to the transmitting coil (d), which is held in place by a magnet. The coil transmits the digitized information across the skin to the internal receiver/stimulator (e). The internal receiver/stimulator decodes the incoming signal and sends information in each frequency band to a different electrode within the cochlea (f). (The internal receiver/stimulator also contains a magnet to which the external coil sticks.) High-frequency information is sent to electrodes in the basal end of the cochlea (f), and low-frequency information is sent to electrodes in the apical end of the cochlea (g). Electrical stimulation from the intracochlear electrodes takes the place of damaged cochlear structures or hair cell - nerve synapses. The auditory nerve (h) picks up the electrical signals from the electrodes and relays that information to the brain where it is interpreted as sound.