Coding of sounds in the auditory system and its relevance to signal processing and coding in cochlear implants

Objective: To review how the properties of sounds are “coded” in the normal auditory system and to discuss the extent to which cochlear implants can and do represent these codes. Data Sources: Data are taken from published studies of the response of the cochlea and auditory nerve to simple and com-plex stimuli, in both the normal and the electrically stimulated ear. Review Content: The review describes: 1) the coding in the normal auditory system of overall level (which partly deter-mines perceived loudness), spectral shape (which partly deter-mines perceived timbre and the identity of speech sounds), periodicity (which partly determines pitch), and sound location; 2) the role of the active mechanism in the cochlea, and par-ticularly the fast-acting compression associated with that mechanism; 3) the neural response patterns evoked by cochlear implants; and 4) how the response patterns evoked by implant