Figure 1: Function of a cochlear implant system:
Sound is picked up by a microphone (1), processed by the external speech processor (2) and wirelessly transmitted by a transmitter (3) to an implantable receiver (4). The electrical signal, coding e.g. speech or music as a defined sequence of electrical pulses, is then relayed to an electrode (5). The electrode is inserted through the mastoid, the facial recess, past the facial nerve through the middle ear into the non-functional cochlea (6). The electrode carrier stimulates the auditory nerve. The brain decodes the relayed neural impulse and the original signal is recognised as speech or music (schematic taken from product information).