Multichannel implantable inner ear stimulator

• US 6,175,767 B1
• Filed: 03/31/1999
• Issued: 01/16/2001
• Est. Priority Date: 04/01/1998
• Status: Expired due to Fees

• Current Assignee: James H. Doyle Sr
• Original Assignee: James H. Doyle Sr
• Inventors: Doyle, James H. Sr.
• Primary Examiner(s): LAYNO, CARL HERNANDZ
• Application Number:
  US09/282,363
• Time in Patent Office: 657 Days
• Field of Search: 607/55-57
• US Class Current: 607/57
• CPC Class Codes: A61F 2/18 Internal ear or nose parts, e.g. ear-drums implants for middle ear ventilation or drainage A61F11/202
• CPC Class Codes: A61N 1/36036 of the outer, middle or inner ear
• CPC Class Codes: A61N 1/36038 Cochlear stimulation

Abstract

A device is described for stimulating the auditory transmission branch of the 8^th nerve. It uses electrodes designed to restrict the electrical field to the region of their respective nerve fiber group and produce a gradient field for each channel such that the latency characteristics of the nerve fibers in a given channel will cause a sequential firing (streaming) of the nerve fibers during a portion of the channel stimulus pulse. In the analog system the nerve fiber channels are stimulated in sequence but with their stimulus overlapping their previous channel by an amount equal to the shortest latency period of said channel. During the period when a stimulus pulse is causing nerve fiber streaming the pulse amplitude is modulated with the audio information. In addition during the nerve fiber streaming either electrical means or the shape of the probe compensate for the strength-duration characteristics of the individual nerve fibers. In the digital system there is no streaming as there is a single firing time for nerve fibers in a channel. The channel overlap exists over a number of channels and the audio modulation is in the form of frequency modulation of the channel sequence frequency.

Claims

1. A device for applying electrical stimuli to any branch of the 8th nerve, comprising:

a stimulus generator for applying electrical stimuli to nerve fibers of the 8th nerve during at least two time channels so as to produce or enhance a stream of nerve activity at a generally constant rate, independent of audio modulation, that is capable of acting as a carrier wave and that is perceived by the brain as active silence.

2. A device according to claim 1, wherein:

the stimulus generator applies electric fields to at least two groups of nerve fibers to cause fibers in each group to stream at a generally uniform rate.

3. A device according to claim 2, wherein the stimulus generator applies a time varying electric field to each group of fibers that compensates for the strength-duration characteristics of the fibers in the group in order to cause the fibers in the group to stream at said generally uniform rate.

4. A device according to claim 2, wherein the stimulus generator applies a space varying electric field to each group of fibers that compensates for the strength-duration characteristics of the fibers in the group in order to cause the fibers in the group to stream at said generally uniform rate.

5. A device according to claim 2, wherein the stimulus generator includes:

a plurality of electric field generators, each electric field generator being positioned adjacent a respective one of the group of nerve fibers for applying electric fields to said adjacent group of nerve fibers; and

a signal generator to apply signals to the electric field generators to cause the electric field generators to apply electric fields to the nerve fibers so as to produce or enhance the stream of nerve activity at the generally constant rate.

6. A device according to claim 1, wherein the stimulus generator includes means to modulate the carrier wave to produce the sensation of sound.

7. A device according to claim 6, wherein:

each stimuli is applied during one of the time channels to an associated group of the nerve fibers;

each time channel includes a latency period and a streaming period;

when one of the stimuli is applied to the associated group of nerve fibers during one of the time channels, the fibers in the associated group of fibers stream at a generally uniform rate during the streaming period of the time channel to produce or to enhance the carrier wave, and the means to modulate the carrier wave modulates said one electric stimuli during the streaming period of said one of the time channels.

8. A device according to claim 2, wherein:

each stimulus is applied during one of the time channels to one of the groups of fibers;

each time channel includes a latency period;

when one of the stimuli is applied to one of the groups of fibers during one of the time channels, said one of the stimuli includes compensation for the strength-duration characteristics of the fibers in said one group to cause the fibers in the group to stream at the generally uniform rate, and said compensation for the strength-duration characteristics occurs after the latency period of said one of the time channels.

9. A device according to claim 1, wherein the stimulus generator applies electric fields to a multitude of sets of nerve fibers to cause fibers in each set to fire substantially simultaneously.

10. A device according to claim 1 wherein the stimulus generator applies stimuli to a multitude of groups of nerve fibers to produce said stream of nerve activity.

11. A device according to claim 10, wherein:

the stimulus generator applies electric fields to the groups of nerve fibers to cause fibers in each group to stream at a generally uniform rate.

12. A device according to claim 11, wherein:

the stimulus generator applies electric fields to each of the groups of nerve fibers for a respective one time channel and in a defined sequence, and wherein channels adjacent in time overlap in time to compensate for a latency period in the firing of nerve fibers.

13. A device according to claim 12, wherein pairs of channels adjacent in time overlap for a substantially constant length of time.

14. A device according to claim 12, wherein:

over a defined cycle time, the stimulus generator applies electric fields to a number of the groups of fibers; and

in such defined cycle time, the stimulus generator does not apply electric fields to each group of fibers for a rest period of time to provide the nerve fibers in each group with a recovery time.

15. A device according to claim 12, wherein:

over a defined cycle time, the stimulus generator applies electric fields to a given number of the groups of fibers; and

in such defined cycle time, the stimulus generator applies electric fields to all said given number of the groups of fibers for a generally equal length of time.

16. A device for applying electrical stimuli to any branch of the 8th nerve, comprising:

a stimulus generator for applying electrical stimuli to a multitude of sets of nerve fibers of the 8th nerve during a multitude of time channels, to cause the fibers in each set to fire substantially simultaneously and to produce a stream of nerve activity at a generally constant rate, independent of audio modulation, that is capable of acting as a carrier wave and that is perceived by the brain as active silence.

17. A device according to claim 16, wherein the amplitude of the electrical stimulus is such that each set of fibers fires within about 120 microseconds after one of the stimulus is applied to the set of fibers.

18. A device according to claim 16, wherein:

the stimulus generator applies electric fields to each of the sets of nerve fibers during a respective one time channel and in a defined sequence, and wherein channels adjacent in time overlap in time to compensate for a latency period in the firing of the nerve fibers.

19. 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.

20. A device according to claim 19, wherein:

the means to apply the electric fields applies a time varying electric field to each group of fibers that compensates for the strength-duration characteristics of the fibers in the group in order to cause the fibers in the group to stream at a generally uniform rate.

21. A device according to claim 20, wherein:

the means to apply the electric fields applies electric fields to pairs of groups of fibers for an overlapping period of time to compensate for a latency period in the firing of nerve fibers.

22. A method for applying electrical stimuli to a branch of the 8th cranial nerve, comprising:

using a stimulus generator to apply electrical stimuli to nerve fibers of the 8th cranial nerve during at least two time channels so as to produce or enhance a stream of nerve activity at a generally constant rate, independent of audio modulation, that is capable of acting as a carrier wave and that is perceived by the brain as active silence.

23. A method according to claim 22, wherein:

the step of using the stimulus generator includes the step of applying electric fields to at least two groups of nerve fibers to cause fibers in each group to stream at a generally uniform rate.

24. A method according to claim 23, wherein the step of using the stimulus generator further includes the step of applying a time varying electric field to each group of fibers that compensates for the strength duration characteristics of the fibers in the group in order to cause the fibers in the group to stream at said generally uniform rate.

25. A method according to claim 23, wherein the step of using the stimulus generator includes the steps of:

positioning a respective one electric field generator adjacent each of the groups of nerve fibers for applying electric fields to said adjacent group of nerve fibers; and

using a signal generator to apply signals to the electric field generators to cause the electric field generators to apply electric fields to the nerve fibers so as to produce said generally constant stream of nerve activity.

26. A method according to claim 22, further comprising the step of modulating the carrier wave to produce the sensation of sound.

27. A method according to claim 22, wherein the step of using the stimulus generator includes the step of applying stimuli to a multitude of channels of fibers to produce said stream of nerve activity.

28. A method according to claim 27, wherein the step of using the stimulus generator includes the steps of:

applying electric fields to each of the groups of nerve fibers for a respective one time channel and in a defined sequence; and

overlapping adjacent channels in time to compensate for a latency period in the firing of nerve fibers.

29. A method according to claim 28, wherein pairs of channels adjacent in time overlap for a substantially constant length of time.

30. A method according to claim 28, wherein the step of using the stimulus generator further includes the steps of:

over a defined cycle time, applying electric fields to a number of the groups of fibers; and

in such defined cycle time, providing each group of fibers with a rest period, wherein the electric fields are not applied to the group of fibers, to provide the nerve fibers in each group with a recovery time.

31. A method according to claim 28, wherein:

over a defined cycle time, the stimulus generator applies electric fields to a given number of the groups of fibers; and

in such defined cycle time, the stimulus generator applies electric fields to all said given number of the groups of fibers for a generally equal length of time.

32. 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.