Multichannel cochlear prosthesis with flexible control of stimulus waveforms

• US 6,219,580 B1
• Filed: 05/28/1999
• Issued: 04/17/2001
• Est. Priority Date: 04/26/1995
• Status: Expired due to Term

• Current Assignee: Advanced Bionics AG (Sonova Holding AG)
• Original Assignee: Advanced Bionics Corporation (Sonova Holding AG)
• Inventors: Loeb, Gerald E., Palmer, Logan P., Faltys, Michael A., Voelkel, Andrew W.
• Primary Examiner(s): LAYNO, CARL HERNANDZ
• Application Number:
  US09/322,711
• Time in Patent Office: 690 Days
• Field of Search: 607/55-57
• US Class Current: 607/57
• CPC Class Codes: A61N 1/36038 Cochlear stimulation

Abstract

A cochlear implant system includes an implant portion and an external portion. The external portion performs at least the function of sensing acoustic signals and converting such sensed signals to electrical signals. The implant portion performs at least the function of generating electrical stimuli, modulated and classified in response to the sensed acoustic signals, and intended for direct electrical stimulation of the auditory nerve in accordance with a selected speech processing strategy. Control data defines the selected speech processing strategy, i.e., the pulsatile stimulation pattern to be used by implantable portion. Such control data is transmitted to and stored within the implantable portion of the system only once, when a particular speech processing strategy is selected, thereby eliminating the need to continually resend such speech-processing-defining data over a bandwidth-limited link between the implantable and external portions of the system. The control data that defines the selected speech processing strategy is stored in a stimulation template (also referred to as a “pulse table”), which template or table is stored digitally within the implanted portion of the system. Weighting coefficients (or weighting factors) are stored in the template or table at specified locations to define the speech processing strategy. For example, the columns of the template or table may be used to represent the different current sources, or “stimulous channels”, of the implanted portion, and the rows may be used to represent intervals of time. The “stimulous channels” and increments of time thus form the two ordinates of the table, and the table thus consists of a modest number of intervals whose total duration defines a complete “cycle” of stimulation. The instantaneous current flow to be generated by the implanted portion is defined at the beginning of each stimulation cycle by multiplying the weighting factor stored in a particular location within the pulse table by modulation data derived from the sensed acoustic signal. Only modulation data need be sent to the implanted portion on a continuous (real time) basis for the cochlear implant system to function.

Claims

1. A cochlear implant system comprising:

an external portion that includes

an acoustic transducer for sensing acoustic signals and converting them to electrical signals, and

analog front end (AFE) circuitry for preliminarily processing the electrical signals produced by the acoustic transducer;

an implantable portion that includes

an electrode array having a plurality of spaced-apart electrodes for implantation in the cochlea, and

an implantable cochlear stimulator (ICS) connected to the electrode array for generating electrical stimuli defined by control signals; and

a speech processor (SP) that generates the control signals used by the ICS;

wherein the electrical stimuli generated by the ICS are modulated by the sensed acoustic signals in accordance with a selected speech processing strategy; and

further wherein

a portion of the speech processor responsible for defining a portion of the speech processing strategy is located within the implantable portion of the system;

whereby only modulation data corresponding to the sensed acoustic signals need be continuously sent to the implantable portion of the system from the external portion of the system during use of the system.

2. The cochlear implant system of claim 1 wherein the portion of the speech processor included within the implantable portion of the system comprises:

a pulse table wherein a set of coefficients are stored that represent a particular spatiotemporal pattern of stimulus waveforms, and

a modulator that multiplies the set of coefficients stored in the pulse table with modulation data derived from the sensed acoustic signals to produce a product signal;

wherein the product signal specifies a particular spatiotemporal pattern of controlled stimulus waveforms associated with the selected speech processing strategy.

3. The cochlear implant system of claim 2 wherein the pulse table comprises a pulse table random access memory (RAM).

4. The cochlear implant system of claim 3 wherein the pulse table RAM comprises an m by n array, where m and n are each integers of at least sixteen.

5. The cochlear implant system of claim 4 wherein n has a value of at least sixteen and m has a value of at least 128.

6. The cochlear implant system of claim 5 further including an amplitude buffer wherein the modulation data is stored as a multiplicity of amplitude words, and further wherein the pulse table RAM stores m pulse table words of at least sixteen bits each, and wherein each bit of the pulse table word belongs to one of multiplicity of fields, and wherein a first of the multiplicity of fields identifies a coefficient to be used by the multiplier, and a second of the multiplicity of fields identifies which of the multiplicity of amplitude words is to be multiplied by the coefficient.

7. The cochlear implant system of claim 6 wherein a third of the multiplicity of fields of the pulse table words identifies which one of the plurality of electrodes on the electrode array is to be acted upon by the product signal obtained from the modulator.

8. The cochlear implant system of claim 7 wherein a fourth of the multiplicity of fields of the pulse table words identifies a bypass flag (PASS), which when set causes the selected amplitude word to bypass the multiplier, thereby effectively producing a “

multiply by 1”

condition.

9. The cochlear implant system of claim 2 further including

a neural conditioning pattern stored in a selected location within the pulse table,

a digital signal generator responsive to the neural conditioning pattern stored in the pulse table that generates a neural conditioning signal;

an adder that adds the neural conditioning signal to the modulation data.

10. An implantable cochlear stimulator (ICS) comprising:

an electrode array having a plurality of spaced-apart electrodes for implantation in the cochlea,

a plurality of pulse generators, wherein each of the pulse generators is connected to a respective one of the plurality of spaced-apart electrodes, and further wherein each pulse generator generates a current having an amplitude and polarity defined by a control signal;

a pulse table wherein a multiplicity of pulse data words are stored;

an amplitude buffer wherein a plurality of amplitude words are stored, wherein each amplitude word contains modulation data associated with an externally sensed acoustic signal;

a multiplier coupled to the pulse table and amplitude buffer that multiplies selected portions of a designated amplitude word with a specified pulse data word, the product of said multiplication comprising a control word;

means for directing information contained in the control word to an identified one of said plurality of pulse generators, wherein the control word defines the control signal for the pulse generator to which it is directed;

timing means for controlling when the multiplier and means for directing perform their respective operations;

whereby the pulse data words stored in the pulse table control the spatiotemporal characteristics of the currents generated by the plurality of pulse generators.

11. The ICS as set forth in claim 10 further including means for updating in real time the amplitude words stored in the amplitude buffer, whereby the spatiotemporal characteristics of the currents generated by the plurality of pulse generators may be modulated by information contained within the amplitude words.

12. The ICS as set forth in claim 11 wherein a portion of the pulse data words stored in the pulse table words identifies a bypass flag, which when set causes the modulation data contained within the designated amplitude word to bypass the multiplier, thereby effectively producing a “

multiply by 1”

condition.

13. The ICS as set forth in claim 11 further including means for updating the pulse data words stored in the pulse table, whereby the spatiotemporal characteristics of the currents generated by the plurality of pulse generators may be modified.

14. The ICS as set forth in claim 11 further including:

a neural conditioning pattern stored in a selected location within the pulse table,

a digital signal generator responsive to the neural conditioning pattern stored in the pulse table that generates a neural conditioning signal;

an adder that adds the neural conditioning signal to a selected one of the amplitude words stored in the amplitude buffer.

15. A method of electrically stimulating the cochlea so as to directly stimulate the auditory nerve, thereby producing the sensation of hearing for a deaf patient, the method comprising:

implanting within the patient an electrode array within the cochlea of the patient, the electrode array having a plurality of spaced-apart electrodes;

implanting within the patient a plurality of pulse generators, wherein each of the pulse generators is connected to a respective one of the plurality of spaced-apart electrodes, and further wherein each pulse generator generates a current having an amplitude and polarity defined by a control signal;

implanting within the patient a pulse table wherein a multiplicity of pulse data words are stored, the pulse data words stored in the pulse table containing information that, when acted upon, defines the spatiotemporal characteristics of the currents generated by the plurality of pulse generators, and thereby defines a particular speech processing strategy to be implemented by the method;

implanting within the patient an amplitude buffer wherein a plurality of amplitude words are stored;

sensing acoustical signals external to the patient, and converting the sensed acoustical signals to modulation data;

sending the modulation data, in real time, to the implanted amplitude buffer;

implanting within the patient a multiplier that multiplies selected portions of a designated amplitude word with a specified pulse data word, the product of said multiplication comprising a control word;

directing information contained in the control word to an identified one of said plurality of pulse generators, wherein the control word defines the control signal for the pulse generator to which it is directed;

controlling the timing of when the multiplier multiplies the amplitude words with the pulse data words, and when the resulting control is directed to the pulse generators;

whereby the pulse data words stored in the pulse table, coupled with the controlled timing applied thereto, define the particular spatiotemporal characteristics of the currents generated by the plurality of pulse generators, and further whereby the currents thus generated by the plurality of pulse generators may be modulated with information contained within the amplitude words.