Multichannel implantable inner ear stimulator

A device for applying electrical stimuli to a branch of the 8th cranial nerve, comprising in combination:

• means for stimulation of a number (N) of different groups of nerve fibers of the 8th cranial nerve, said groups of nerve fibers being phased in N spaced intervals;
• and
• means for repeatedly applying electric fields to the fiber groups to produce or enhance a constant stream of nerve activity, independent of audio modulation, that is capable of acting as a carrier wave and that is perceived by the brain as active silence;
• and wherein the carrier wave, when modulated, results in the perception of sound;
• and
• wherein, for each fiber group, an interval is provided between applications of the electric fields to the fiber group, and said interval is not less than the natural recover time of the nerve fibers in the group.

A method of directly stimulating nerve fibers of the 8th cranial nerve with electrical signals representative of sensed audio sounds in sequence to impart the sensation of hearing to a deaf patient, the method comprising the steps of:

• implanting in the patient a receiver with an antenna and with connections to an electrode probe, comprised of an array of electrodes formed to produce multiple gradient fields in the area of the cochlear nerve;
• generating an electrical signal representative of sensed audible sounds;
• dividing the electrical signal into time multiplexed channels, wherein each multiplexed channel is connected to a corresponding gradient probe channel and contains the audible representation of the entire audio spectrum and means for limiting the audio spectrum;
• processing each channel to produce a bi-phasic stimulation signal that overlaps a time adjacent channel bi-phasic stimulation signal but does not overlap its component that is representative of audible sounds;
• aligning an external transmitter/receiver antenna with the implanted antenna such that there is a distance at least equal to the thickness of the patient's skin separating the external antenna from the internal antenna, wherein said external antenna provides a means of transmitting both power and audible sound representations to the implanted receiver;
• locating the gradient probe in proximity to the nerve fibers that transmit sound sensations to the brain;
• and
• permanently fixing the gradient probe in place in the patient.