Optimizing pitch allocation in a cochlear implant

• US 20050137651A1
• Filed: 11/17/2004
• Published: 06/23/2005
• Est. Priority Date: 11/21/2003
• Status: Active Grant

• Current Assignee: Advanced Bionics AG (Sonova Holding AG)
• Original Assignee: Advanced Bionics LLC (Sonova Holding AG)
• Inventors: Litvak, Leonid M., Mishra, Lakshmi N.
• Granted Patent: US 7,702,396 B2
• Time in Patent Office: Days
• US Class Current: 607/57
• CPC Class Codes: A61N 1/36038 Cochlear stimulation
• CPC Class Codes: A61N 1/37247 User interfaces, e.g. input or presentation means
• CPC Class Codes: H04R 2225/67 Implantable hearing aids or parts thereof not covered by H04R25/606

Abstract

Errors in pitch allocation within a cochlear implant are corrected in order to provide a significant and profound improvement in the quality of sound perceived by the cochlear implant user. The disclosure provides a tool for determining the implant fitting curve for cochlear implant system to correct pitch warping. The method presents familiar musical tunes to determine the implant fitting slope (relative alignment). In addition, in one embodiment, speech sounds may be used to determine the offset of the fitting line (absolute alignment). The use of music and speech to determine the implant fitting curve (line) and the slope is facilitated by using techniques to implement virtual electrodes to more precisely direct stimuli to the location or “place” on the cochlea.

Claims

1. A method for fitting a cochlear implant system, the method comprising:

implanting a multi-electrode array into the cochlea of a user, the multi-electrode array having an associated implant fitting line that defines a relationship between cochlear places of implant electrodes and associated audio frequencies;

presenting variations of a musical melody to the user through the multi-electrode array;

allowing the user to select a variation of the musical melody that most closely conforms to a musical melody as remembered by the user; and

determining a correct slope of the implant fitting line of the multi-electrode array based on the rendition of the musical melody selected by the user.

2. The method of claim 1, wherein presenting variations of the musical melody comprises repetitively presenting the musical melody to the user with a different slope of the implant fitting line at each presentation such that the user perceives a different rendition of the musical melody for each presentation of the musical melody.

3. The method of claim 2, further comprising determining an offset of the implant fitting line relative to an intrinsic fitting line of the user'"'"'s cochlea by repetitively presenting a familiar sound to the user, while varying the offset of the implant fitting line, through the multi-electrode array and allowing the user to select a familiar sound with a particular offset, such that the familiar sound with the particular offset is most like the sound as remembered.

4. The method of claim 3, wherein virtual electrodes are implemented to precisely deliver stimuli to places on the cochlea while delivering tunes or sounds to the user.

5. The method of claim 4, wherein the virtual electrodes are implemented by presenting weighted stimulus currents simultaneously at two electrodes.

6. The method of claim 4, wherein the virtual electrodes are implemented by presenting rapidly alternating stimulus currents at two closely spaced electrodes, in a time-multiplexed manner.

7. The method of claim 1, wherein presenting variations of the musical melody comprises varying the frequency of one or more of the notes of the melody in a predetermined manner to present a distorted version of the musical melody to the user.

8. The method of claim 7, wherein the rendition of the musical melody that most closely conforms to the musical melody as remembered by the user is a distorted version of the musical melody that sounds correct to the user if the multi-electrode array is mistuned.

9. The method of claim 7, wherein determining a correct slope of the implant fitting line of the multi-electrode array based on the rendition of the musical melody selected by the user comprises using differences in relative frequencies between an original version of the musical melody and the distorted version of the musical melody to determine the correct slope

12. The method of claim 1,0 wherein the step (b) of determining the slope comprises:

using a converging process wherein further incremental changes to the slope do not yield appreciable perceived improvement in the quality of the tune presented, in which event a best slope has been found.

10. A method for fitting a cochlear implant system, the method comprising:

(a) implanting a multi-electrode array into the cochlea of a user;

(b) determining a best slope of an implant fitting line by repetitively presenting a musical tune to the user, while varying the slope of the implant fitting line, through the multi-electrode array, wherein the implant fitting line defines a relationship between cochlear places of implant electrodes and associated audio frequencies;

(c) allowing the user to select a tune with a particular implant fitting line slope that is most like the tune as remembered by the user; and

(d) determining an offset of the implant fitting line relative to an intrinsic fitting line of the user'"'"'s cochlea by repetitively presenting a familiar sound to the user, while varying the offset of the implant fitting line, through the multi-electrode array, and allowing the user to select a familiar sound with a particular offset, such that the familiar sound with the particular offset is most like the sound with the pitch as remembered,

wherein virtual electrodes are implemented to precisely deliver stimuli to places on the cochlea while delivering tunes or sounds to the user.

11. The method of claim 10, wherein the familiar sound presented in step (c) is human speech.

13. The method of claim 10, wherein the virtual electrodes are implemented by presenting weighted stimulus currents simultaneously at two electrodes.

14. The method of claim 10, wherein the virtual electrodes are implemented by presenting rapidly alternating stimulus currents at two closely spaced electrodes, in a time-multiplexed manner.

15. The method of claim 10, wherein the step (b) of determining the slope comprises:

presenting the same first note of a tune at the same electrode, without using a virtual electrode, or at the same cochlear place, using a virtual electrode.

16. The method of claim 10, wherein the step of determining the slope and the step of determining the offset of the implant fitting line are both accomplished by using displayed menu interfaces for a computer software program.

17. The method of claim 16, wherein the step of determining the slope is accomplished by storing different values of slopes in a computer memory and presenting the selected tune with the musical tune using different values of the slopes.

18. The method of claim 10, wherein the electrode array is placed in the scala tympani and the electrode array includes at least eight electrode contacts with even inter-electrode spacing.

19. A method for finding the slope of an implant fitting line, the method comprising:

(a) implanting a multi-electrode array into the cochlea of a user;

(b) determining the slope of an implant fitting line by repetitively presenting a musical tune to the user, but with different slopes at each presentation, through the multi-electrode array and allowing the user to select a tune with a particular slope that is most like the tune as remembered, wherein the implant fitting line defines a relationship between cochlear places of implant electrodes and associated audio frequencies,

wherein virtual electrodes are implemented to precisely deliver stimuli to places on the cochlea while delivering tunes to the user.

20. The method of claim 19, wherein

the step (b) is performed by incrementally changing the slope of the tune presented until further incremental changes to the slope do not yield appreciable improvement in the quality of the tune as remembered, in which event the best slope has been found.

21. A cochlear implant system comprising:

an implantable pulse generator;

an electrode array having a multiplicity of electrodes connected to the implantable pulse generator;

means for generating a musical tune delivered through the electrode array with different slopes; and

means for implementing virtual electrodes.

22. The cochlear implant system of claim 21 further comprising:

means for adjusting the slope of the implant fitting line embodied in presenting the familiar tune;

means for generating a familiar sound having a recognizable pitch; and

means for adjusting the offset of the implant fitting line.

23. The cochlear implant system of claim 22, wherein the familiar sound is human speech.

24. The cochlear implant system of claim 21, wherein the means for implementing virtual electrodes are stimulation channels that deliver current-controlled stimuli to each electrode that are independently settable for pulsewidth, amplitude and onset of stimulus delivery.

25. The cochlear implant system of claim 21, wherein the means for implementing virtual electrodes is a stimulus delivery circuit that permits rapid delivery of alternating, non-simultaneous stimuli at two, closely-spaced electrodes.

26. A method for fitting a cochlear implant system, the method comprising:

(a) implanting a multi-electrode array into the cochlea of a user;

(b) presenting a first musical melody to a user through the multi-electrode array, the first musical melody comprising a series of notes, each note having a predetermined frequency and duration;

(c) varying the frequency of one or more of the notes of the first melody in a predetermined manner to present a second musical melody to the user, the second musical melody being a distorted version of the first musical melody, wherein the user perceives that the second musical melody conforms to a musical melody remembered by the user; and

(d) adjusting an implant fitting line of the multi-electrode array based on the variation between the first musical melody and the second musical melody, wherein the implant fitting line defines a relationship between cochlear places of implant electrodes and associated audio frequencies.

27. The method of claim 26, wherein the first musical melody comprises an original version of a well-known melody and wherein the second musical melody comprises a distorted version of the original melody.

28. The method of claim 27, wherein adjustment of the implant fitting line causes the first musical melody to conform to the musical melody remembered by the user when presented to the user via the multi-electrode array.

29. The method of claim 26, wherein varying the frequency of one or more of the tones of the first melody comprises assigning the frequency of a first note of the first melody to a predetermined electrode of the array and then varying the frequencies of subsequent notes in the first melody relative to the assigned frequency.

30. The method of claim 29, further comprising, for all notes in the first musical melody, calculating a difference in frequency relative to the first note, multiplying the difference by a correction factor, and adding the multiplied difference to the frequency of the first note to arrive at the second musical melody.

31. The method of claim 30, wherein the correction factor represents the variation between the first musical melody and the second musical melody.

32. The method of claim 30, further comprising varying the correction factor to achieve variations of the second musical melody, and then presenting the variations of the second musical melody to the user to arrive at an optimal correction factor.

33. The method of claim 26, further comprising varying the frequency of one or more of the notes of the first melody relative to the frequencies assigned to various electrodes in the array, wherein the implant fitting line is adjusted differently based on a location along the electrode array.

34. A method of fitting a cochlear implant system, the method comprising:

implanting a multi-electrode array into a cochlea of a user, the electrodes being positioned on the array to have a spatial relationship with associated audio frequencies corresponding to positions along the user'"'"'s cochlea;

presenting two or more variations of a sound to the user through the multi-electrode array;

allowing the user to select a desired variation of the sound; and

based on the variation selected by the user, determining a correct fitting of the multi-electrode array relative to the user'"'"'s cochlea.

35. The method of claim 34, wherein the sound comprises a musical melody.

36. The method of claim 35, wherein presenting variations of a sound comprises repetitively presenting the musical melody to the user with a different slope of an implant fitting line at each presentation such that the user perceives a different rendition of the musical melody for each presentation of the musical melody, the implant fitting line defining a relationship between cochlear places of implant electrodes and associated audio frequencies .

37. The method of claim 36, further comprising determining an offset of the implant fitting line relative to an intrinsic fitting line of the user'"'"'s cochlea by repetitively presenting a familiar sound to the user, while varying the offset of the implant fitting line, through the multi-electrode array and allowing the user to select a familiar sound with a particular offset, such that the familiar sound with the particular offset is most like the sound as remembered.

38. The method of claim 35, wherein presenting variations of a sound comprises varying the frequency of one or more of the notes of the melody in a predetermined manner to present a distorted version of the musical melody to the user.

39. The method of claim 36, wherein the rendition of the musical melody that most closely conforms to the musical melody as remembered by the user is a distorted version of the musical melody that sounds correct to the user if the multi-electrode array is mistuned.