Cochlear implant system for an auditory prosthesis

• US 4,532,930 A
• Filed: 04/11/1983
• Issued: 08/06/1985
• Est. Priority Date: 04/11/1983
• Status: Expired due to Term

• Current Assignee: Department of Science and Technology
• Original Assignee: Commonwealth of Australia Dept of Science & Technology
• Inventors: Patrick, James F., Kuzma, Janusz A., Crosby, Peter A., Seligman, Peter M., Money, David K., Daly, Christopher N.
• Primary Examiner(s): Coven, Edward M.
• Application Number:
  US06/483,806
• Time in Patent Office: 848 Days
• Field of Search: 128/419 E, 128/421, 128/422, 128/1 R, 128/419 R, 128/184, 128/185, 179/1, 179/107 E, 179/107 BC
• US Class Current: 607/57
• CPC Class Codes: A61N 1/36038 Cochlear stimulation
• CPC Class Codes: A61N 1/36039 fitting procedures
• CPC Class Codes: A61N 1/36185 Selection of the electrode configuration

Abstract

A cochlear implant system includes an electrode array (1) comprising multiple platinum ring electrodes in a silastic carrier to be implanted in the cochlea of the ear. A receiver-stimulator (3) containing a semiconductor integrated circuit and other components is implanted in the patient adjacent the ear to receive data information and power through tuned coil (5) using an inductive link (6) from a patient-wearable external speech processor (7) including an integrated circuit and various components which is configured or mapped to emit data signals from an EPROM programmed to suit each patient electrical stimulation perceptions through testing of the patient and his implanted stimulator/electrode using a diagnostic and programming unit (12) connected to the processor by an interface unit (10). The system allows use of various speech processing strategies including dominant spectral peak and amplitude and compression of voice pitch so as to include voiced sounds, unvoiced glottal sounds and prosodic information. Biphastic pulses are supplied to various combinations of electrodes by a switch controlled current sink in various modes of operation. In-place testing of the implant is also provided. Various safety features are incorporated to insure that harmful impulses are not imposed on the patient.

Transmission of data is by a series of discrete data bursts which represent the chosen electrode(s), the electrode mode configuration, the stimulating current, and amplitude determined by the duration of the amplitude burst.

Claims

1. In a cochlear implant system having a sound-to-electrical stimulation encoder means, a body-implantable receiver-stimulator and electrodes for receiving electrical signals from said encoder means, the improvement comprising

means in said receiver-stimulator for preventing the delivery of a stimulation signal to the electrodes except after the receipt of a correct predetermined sequence of numerical information from said encoder means and

means in said encoder means for encoding each item of numerical information as a number of pulses in a burst of pulses.

2. The cochlear implant system of claim 1 wherein the receiver-stimulator includes means for dividing the number of received pulses in each burst of pulses by an integer, thus decoding the numerical information transmitted.

3. The cochlear implant system of claim 1 including at least one cochlear electrode array and means for independently controlling the current amplitudes, burst rate, pulse separation and pulse widths of the stimulation signal to be delivered to said electrodes, said stimulation signal comprising pulses of an equal amplitude biphasic stimulus current waveform.

4. The cochlear implant system of claim 3 wherein each of said pulses of said waveform has equal pulse widths.

5. The cochlear implant system of claim 3 including one current source for determining the current during both phases of the biphasic stimulus current pulse.

6. The cochlear implant system of claim 3 including a single current source for providing stimulus signals for all electrodes.

7. In a cochlear implant system having a speech processor located external to a patient'"'"'s body, said speech processor including sound-to-stimulation encoding means, a body-implantable receiver-stimulator and an electrode array implantable in the cochlea of a patient for receiving electrical signals from said encoding means, the improvement comprising

means for performing psychophysical testing on the auditory nervous system of the patient while said receiver-stimulator is receiving said electrical signals,

means, using the results of said testing, for preparing data in a map representing a patient stimulation strategy;

means for converting audio signal information to electrical signals in said sound-to-stimulation encoding means for that patient; and

means for erasably programming and storing said mapped data in said encoding means, such that stimulation parameters for speech signals are optimized utilizing said stored data to enhance the ability of the patient to recognize speech signals.

8. The cochlear implant system of claim 7 including patient operated controls in said testing means for determining stimulation thresholds and comfort levels.

9. The cochlear implant system of claim 7 in which said sound-to-stimulation encoding means includes memory means fixed in said encoding means for storing said mapped data in said encoding means.

10. The cochlear implant system of claim 9 in which said memory means is an erasable programmable read-only-memory.

11. The cochlear implant system of claim 7 in which said means for performing psychophysical testing include means for stimulation, display, and storage of the results of said testing to provide a plurality of electrical stimulation inputs to the auditory nervous system of a patient.

12. The cochlear implant system of claim 7 in which psychophysical testing means includes means for determining the mapping between acoustic parameters and stimulation parameters, and means for testing the mapping before incorporating the mapping into the patient'"'"'s stimulation encoding means.

13. A multichannel cochlear prosthesis system for use with a patient comprising:

a multichannel electrode array suitable for implantation in the ear of a person;

a multichannel stimulator connected to said electrode array, said stimulator being suitable for implantation in said person and being used to provide electrical signals to stimulate said electrode array;

means for encoding sound an electrical stimulation signal, said means for encoding being suitable to be worn externally by said person;

means for transmitting encoded electrical signals representative of speech stimulation parameters from said means for encoding to said multichannel stimulator;

means, external to the patient, for testing the patient'"'"'s psychophysical responses to stimulation of the patient'"'"'s auditory nerves by selected electrical signals applied to said electrode array by said multichannel stimulator through the means for encoding;

means for mapping the psychophysical responses in the form of data of the patient to stimulation of the patient'"'"'s auditory nerves by said selected electrical signals applied to said electrode array by said multichannel stimulator through said means for encoding to optimize the ability of the patient to perceive certain sounds; and

means for storing data from the results of said responses in said means for encoding to encode said data, said results being utilized to determine a relationship between auditory input and said electrical stimulation parameters to optimize the ability of the patient to perceive sounds.

14. The system of claim 13 in which said electrode array comprises series of spaced platinum rings insulated from each other and fixed on a flexible strip carrier of tapering diameter.

15. The system of claim 13 including means in said stimulator for providing a leakage current to electrodes not selected for stimulation of less than 10 microamps.

16. The system of claim 13 in which said electrodes are stimulated with a biphasic constant current thereby to provide zero D.C. current to the electrodes and substantially prevent corrosion problems.

17. The system of claim 13 including selection means for selecting bipolar stimulation of any pair of said electrodes in said array.

18. The system of claim 17 in which said selection means is contained in said encoding means.

19. The prosthesis system of claim 13 wherein said means for mapping includes means for assigning bands of frequency to selected electrodes in said electrode array.

20. The prosthesis system of claim 13 wherein said means for mapping includes means for scaling acoustic loudness perceived by the patient.

22. The prosthesis of claim 20 including means to switch the connections in said current switching means so as to supply biphasic signals of opposite polarity to said electrodes.

23. The prosthesis of claim 20 in which the electrode array is implanted in a patient'"'"'s ear and the electrical signals are indicative of auditory information.

24. The prosthesis of claim 20 including means to connect two electrodes to the current sink and all other electrodes to said power supply.

21. A prosthesis comprising

a multi-electrode array for transmitting electrical stimulations to a patient'"'"'s auditory nerves and adapted to be implantable in a patient,

a patient implantable stimulator means for detecting externally transmitted electrical signals identifying one or more electrodes in said array to act as a source or sink of stimulation current to selected electrodes;

current switching means including a controllable current sink in said stimulator means operable by external signals detected by said stimulator means; and

a power supply in said implantable stimulator means, said power supply being chargeable by an externally generated power supply signal to connect at least two of any of said electrodes variously to said power supply or said current sink.

25. A multichannel cochlear prosthesis system comprising:

a patient implantable tissue stimulating multichannel electrode array;

a patient implantable multichannel stimulator connected to said array;

a patient externally worn sound-to-electrical signal stimulation encoding means, said encoding means including memory means programmable after implantation of said electrode array and said stimulator in a patient;

means for programming said memory means based on the patient'"'"'s auditory perceptions in response to various electrical stimulating pulse signals;

means for transmitting electrical stimulation signals representing speech parameters from said encoding means to said stimulator and to said array for stimulating tissue in accord with said programmed perspections; and

means for controlling said stimulator by said encoding means, such control including varieties of at least one or more of pulse rate, pulse amplitude, pulse duration interval between phases of a biphasic current pulse, and selection of which two of any electrodes stimulus current is to be applied.

26. The system of claim 25 wherein the selection of which electrodes in said electrode array are to be used for stimulation is done in the external sound-to-stimulation encoding means.

27. The system of claim 25 wherein said memory means is a programmable read-only-memory.

28. The system of claim 25 wherein said memory means is an erasable programmable read-only-memory.

29. The system of claim 28 further including means for erasing and reprogramming said memory while it is plugged into said encoding means.

30. The system of claim 25 including means in said encoding means for preventing the delivery of uncomfortable stimuli to the patient.

33. The system of claim 25 wherein said means for programming said memory means includes means for separably attaching said means for programming to said encoding means when it is desired to program the memory means based on the patient'"'"'s perceptions.

34. The system of claim 33 further including acoustic simulation means in said programming means for monitoring the stimulus signals delivered to the implanted stimulator.

35. The system of claim 25 wherein said means to input the memory means includes means to select subsets of up to all of the electrodes in said array to be used for stimulation in response to a given auditory input signal.

36. The system of claim 25 including means for selecting the order of pitch ranking of the electrodes in the array and for programming the encoding means in response to the patient'"'"'s selections of such ranking.

37. The system of claim 25 including means for simultaneous independent selection of particular electrodes for stimulation, the stimulation rate and stimulation amplitude for each stimulation.

38. The system of claim 25 further including means for displaying continuously a visual indication of the electrode selected by the transmitted data from the sound-to-stimulation encoding means for the purpose of monitoring.

39. The system of claim 25 further including means, in the sound-to-stimulation encoding means, for generating information in the form of a known and unvarying train of stimulus pulses from the implantable stimulator and for conducting said pulses to selected electrodes to verify operation of the system.

40. The system of claim 25 in which said means for controlling the stimulator by said encoding means includes means for transmitting and separate means for receiving both power and data representing said pulse signals, said means for receiving power and data including a receiver coil means, said coil means being tunable.

41. The system of claim 40 in which said receiver coil means is coupled via a transformer to a power and data circuit in said stimulator.

42. The system of claim 25 including means in said encoding means for permitting selection of various stimulation strategies.

43. The system of claim 42 wherein said means in said encoding means for permitting selection of various stimulation strategies includes means for encoding the frequency of a second format of an acoustic signal into electrode selection, means for encoding a voicing frequency of said signal into stimulation rate and means for encoding the amplitude of the second formant into stimulation amplitude, each of said encodations being made in said encoding means.

44. The system of claim 42 wherein said means for selection of stimulation strategies includes means for encoding frequency of a second formant of an acoustic signal into electrode selection, means for encoding frequency of a first formant of said signal into stimulation rate and means for encoding the amplitude of the acoustic signal into stimulation amplitude.

45. The system of claim 40 or 41 wherein said means for loading said memory means includes means for choosing an optimal speech processing strategy.

46. The system of claim 25 including means in said encoding means for generating a signal to deactivate the encoding means during periods of relatively constant amplitude acoustic signal.

47. The system of claim 25 including means for configuring the program in said memory means for different patient psychophysical variables.

48. The system of claim 25 including means for preventing operation of said encoding means when an inadequate power supply voltage is present so as to prevent spurious pulses being transmitted to said stimulator.

49. The system of claim 25 including means for preventing delivery of stimuli by the stimulator to the electrode array when a power supply voltage to said stimulator is insufficient to give required voltage compliance to said electrode array.

50. The system of claim 25 including means for programming the memory means while the memory means is connected to said encoding means.

59. The system of claim 25 wherein said stimulator comprises a digital circuit including an error detection circuit to generate signals to a state counter, means for resetting said counter, said state counter being incremented through frame sequences of data bursts from said encoding means by a signal asserted at the end of every data burst other than reset.

60. The system of claim 25 wherein said means for programming said memory means includes means for tailoring each patient'"'"'s perceptions and means for programming said memory means to reflect said perceptions.

61. The system of claim 60 further including means in said sound to-stimulation encoding means for selecting a subset of from one to all of said electrodes for stimulation.

62. The system of claim 25 further including means for providing a monotonic substantially exponentially decreasing relationship between a coded current amplitude of a stimulus to said electrodes and the actual current delivered to said electrodes.

63. The system of claim 62 including means for limiting the maximum current to be delivered to said electrodes.

64. The cochlear system of claim 25 further including means for conveying environmental sounds to the patient.

65. The cochlear system of claim 25 further including means in said encoding means for disabling the generation of speech stimulation signals during a delay period of constant background noise.

66. The cochlear system of claim 65 further including means permitting environmental impulsive, non-speech sounds to enter said encoding means when said encoding means is disabled from receiving speech sounds.

31. The system of claim 31 wherein said means for preventing delivery of uncomfortable stimuli comprises a data map stored in said encoding means wherein the maximum allowable electrical stimulus to the patient capable of being generated by the data in said data map is beneath the level which causes discomfort.

32. The system of claim 31 wherein said means for preventing delivery of uncomfortable stimuli comprises means for providing a common current source for biphasic current stimulation of equal duration and amplitude.

51. The system of claim 31 including pulse burst forming means in said encoding means and means for controlling said pulse burst forming means, said means for controlling including said memory means, said memory means being indicative of the patient auditory perceptions in response to electric stimuli perceived.

52. The system of claim 51 in which said encoding means and said implantable stimulator comprise integrated circuits, the circuit of said encoding means being programmed to produce sequences of constant frequency pulses with the number of pulses and time between pulse bursts being determined by either of said control means.

53. The cochlear system of claim 52 further comprising means for keeping said circuit in a powered state between said data sequences.

54. The system of claim 51 wherein said pulse bursts are formatted in successive frames of data bursts, each frame comprising a reset start burst, an active electrode select burst, an electrode configuration mode burst, an amplitude burst, and two bursts for the two phases of stimulation pulses, and means to provide a time interval between each of said bursts within each said frame.

55. The system of claim 54 including means to utilize the top 10 to 20 dB of the current acoustic stimulus level to determine stimulus amplitude for said amplitude burst.

56. The system of claim 54 further including means to minimize energy consumption by said stimulator to allow said stimulator to be in an active state when subsequent stimulus data frames are transmitted, so as to eliminate the need for a start power pulse in every stimulation frame.

57. The system of claim 51 including a frame of data bursts including two phase simulation bursts of constant time duration.

58. The system of claim 51 further including means in said encoding means for determining amplitude of output current from said stimulator by duration of the pulse burst to control stimulus amplitude and means for reducing said stimulus amplitude by increasing duration of said pulse burst.

67. A speech processor encoding means for a cochlear prosthesis having electrodes for electrical stimulation of auditory nerves comprising

a memory means,

means for generating a data format, indicative of a patient'"'"'s auditory perceptions of sound into said memory means;

means for generating from said data format into a map of electrode stimulation parameters to optimize the patient'"'"'s ability to hear sounds; and

means for programming said resultant map of said parameters into said memory means.

68. The invention of claim 67 including means for preventing burst sequences to said receiver-stimulator of an uncomfortable perception to the patient.