The multiple-channel cochlear implant alleviates a severe-to-profound deafness by stimulating the auditory nerves electrically, and bypassing a damaged or undeveloped organ of Corti, shown here with a loss of the inner and outer hair cells (top). Normally the resulting responses in the auditory nerve to sound are transmitted to the higher brain pathways by numerous fibres which have a complex arrangement (middle and bottom). In the brain the responses are perceived as speech and other sounds. Research showed, however, that with a cochlear implant the electrodes needed to be placed in a fluid-filled compartment beneath the auditory nerves (top), and the passage of the electrical current controlled so that it would not short circuit through the fluid, but pass to separate groups of nerve fibres for multiple-channel stimulation. In addition, innervation of the cochlea by complex and numerous nerve fibres (middle and bottom) raised serious doubts about the possibility of reproducing the temporal and place coding of sound, and was the basis for much of the criticism by the scientific community.