1. Introduction
Complex temporal-spectral patterns of neural activity occur in the peripheral auditory system [1]. In natural hearing, sound stimulates auditory nerve fibers in the cochlea to induce the sensation of hearing. Auditory nerve fibers have intrinsic “characteristic frequencies” (CFs) and are tonotopically organized in the cochlea, i.e., nerve fibers located at deeper sites along the length of the cochlea have lower CFs and thus when they are simulated, lower pitched sounds are perceived. Cochlear implants (CI) exploit this natural phenomenon by providing electrical stimulation across the length of the cochlea via an electrode array, which is blindly threaded into the cochlear bony labyrinth during surgery. Insertion depth of the electrode array, number of electrodes, degree of neuronal survival, positioning and proximity of electrodes to the auditory nerve fibers largely determine which tonotopically mapped groups of nerve fibers are stimulated by each electrode. Variations in the above parameters along with other physiological and cognitive factors, (e.g., age at implantation, duration of deafness and implant use, rehabilitation, to name a few) are key factors responsible for large variations in cochlear implant outcomes.