EP4630105A1

EP4630105A1 - Alternating-polarity stimulation

Info

Publication number: EP4630105A1
Application number: EP23900140.7A
Authority: EP
Inventors: Paul Michael Carter; Oliver John Ridler
Original assignee: Cochlear Ltd
Current assignee: Cochlear Ltd
Priority date: 2022-12-06
Filing date: 2023-11-29
Publication date: 2025-10-15
Also published as: CN120303034A; WO2024121681A1

Abstract

The present invention relates to alternating-polarity focused multipolar stimulation (FMP) techniques for use with medical devices, such as implantable medical devices. Presented herein a method comprising: converting input signals into a plurality of alternating-polarity focused multipolar stimulation signals; and sequentially delivering the plurality of alternating-polarity focused multipolar stimulation signals to a recipient via a first stimulation channel.

Description

ALTERNATING-POLARITY STIMULATION

BACKGROUND

Field of the Invention

[oooi] The present invention relates generally to electrical stimulation in implantable medical devices.

Related Art

[0002] Medical devices have provided a wide range of therapeutic benefits to recipients over recent decades. Medical devices can include internal or implantable components/devices, external or wearable components/devices, or combinations thereof (e.g., a device having an external component communicating with an implantable component). Medical devices, such as traditional hearing aids, partially or fully-implantable hearing prostheses (e.g., bone conduction devices, mechanical stimulators, cochlear implants, etcf pacemakers, defibrillators, functional electrical stimulation devices, and other medical devices, have been successful in performing lifesaving and/or lifestyle enhancement functions and/or recipient monitoring for a number of years.

[0003] The types of medical devices and the ranges of functions performed thereby have increased over the years. For example, many medical devices, sometimes referred to as “implantable medical devices,” now often include one or more instruments, apparatus, sensors, processors, controllers or other functional mechanical or electrical components that are permanently or temporarily implanted in a recipient. These functional devices are typically used to diagnose, prevent, monitor, treat, or manage a disease/injury or symptom thereof, or to investigate, replace or modify the anatomy or a physiological process. Many of these functional devices utilize power and/or data received from external devices that are part of, or operate in conjunction with, implantable components.

SUMMARY

[0004] In one aspect, a method is provided. The method comprises: converting input signals into a plurality of alternating-polarity focused multipolar stimulation signals; and sequentially delivering the plurality of alternating-polarity focused multipolar stimulation signals to a recipient via a first stimulation channel. [0005] In another aspect, a method is provided. The method comprises: receiving input signals at an implantable medical device system; converting the input signals into a plurality of multipolar stimulation signals; and delivering each of the plurality of multipolar stimulation signals to a recipient of the implantable medical device system using only single-polarity stimulation pulses.

[0006] In another aspect, an implantable medical device system is provided. The implantable medical device system comprises: one or more input elements configured to receive environmental signals; one or more processors configured to convert a first portion of the environmental signals into control signals representing at least a first multipolar stimulation signal, and to convert a second portion of the environmental signals into control signals representing at least a second multipolar stimulation signal; and a stimulator unit configured to generate the at least first multipolar stimulation signal and the at least second multipolar stimulation signal from the control signals, and to sequentially deliver the at least first multipolar stimulation signal and the at least second multipolar stimulation signal to a recipient of the implantable medical device via a selected stimulation channel, wherein the at least first multipolar stimulation signal and the at least second multipolar stimulation signal have opposite polarity attributes.

[0007] In another aspect, one or more non-transitory computer readable storage media comprising instructions are provided. The instructions, when executed by a processor, cause the processor to: convert at least a portion of a first sound signal into a first multipolar stimulation signal; cause a stimulator unit to deliver the first multipolar stimulation signal to a recipient via a selected stimulation channel, wherein the first multipolar stimulation signal has a first set of polarity attributes; convert a portion of at least a second sound signal into a second multipolar stimulation signal; and cause a stimulator unit to deliver the second multipolar stimulation signal to a recipient via the selected stimulation channel, wherein the second multipolar stimulation signal has a second set of polarity attributes that are opposite to the first set of polarity

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Embodiments of the present invention are described herein in conjunction with the accompanying drawings, in which:

[0009] FIG. 1 A is a schematic diagram illustrating a cochlear implant system, in accordance with certain embodiments presented herein; [ooio] FIG. IB is a side view of a recipient wearing a sound processing unit of the cochlear implant system of FIG. 1A;

[ooii] FIG. 1C is a schematic view of components of the cochlear implant system of FIG. 1 A;

[0012] FIGs. ID is a block diagram of the cochlear implant system of FIG. 1 A;

[0013] FIG. 2 is a schematic diagram illustrating an example biphasic stimulation signal;

[0014] FIG. 3 is a schematic diagram illustrating an example monophasic stimulation signal;

[0015] FIG. 4 is a schematic diagram illustrating example alternating-polarity focused multipolar stimulation signals, in accordance with certain embodiments presented herein;

[0016] FIG. 5 is another schematic diagram illustrating example alternating-polarity focused multipolar stimulation signals, in accordance with certain embodiments presented herein;

[0017] FIG. 6 is a schematic diagram illustrating a vestibular nerve stimulator, in accordance with certain embodiments presented herein;

[0018] FIG. 7 is a schematic diagram illustrating a retinal prosthesis, in accordance with certain embodiments presented herein;

[0019] FIG. 8 is a flowchart of a method, in accordance with certain embodiments presented herein; and

[0020] FIG. 9 is a flowchart of another method, in accordance with certain embodiments presented herein.

DETAILED DESCRIPTION

[0021] Presented herein are alternating-polarity focused multipolar stimulation (FMP) techniques for use with medical devices, such as implantable medical devices. Merely for ease of description, the alternating-polarity focused multipolar stimulation techniques presented herein are primarily described with reference to a specific implantable medical device system, namely a cochlear implant system. However, it is to be appreciated that the techniques presented herein may also be implemented by other types of implantable medical devices, nonimplantable medical devices, and/or other stimulation devices. For example, the alternating- polarity focused multipolar stimulation techniques may be implemented by other auditory prostheses or systems includes other auditory prostheses, such as middle ear auditory prostheses, bone conduction devices, direct acoustic stimulators, electro-acoustic prostheses, auditory brain stimulators, etc. The techniques presented herein may also be used with tinnitus therapy devices, vestibular devices (e.g., vestibular implants), visual devices (i.e., bionic eyes), sensors, pacemakers, drug delivery systems, defibrillators, functional electrical stimulation devices, catheters, seizure devices (e.g., devices for monitoring and/or treating epileptic events), sleep apnea devices, electroporation devices, etc.

[0022] FIGs. 1A-1D are diagrams illustrating an example cochlear implant system 102 configured to implement certain embodiments of the techniques presented herein. The cochlear implant system 102 comprises an external component 104 and an implantable component 112. In the examples of FIGs. 1A-1D, the implantable component is sometimes referred to as a “cochlear implant.” FIG. lA is schematic diagram illustrating the implantable component 112 implanted in the head 141 of a recipient, while FIG. IB is schematic drawing of the external component 104 worn on the head 141 of the recipient. FIG. 1C is another schematic view of the cochlear implant system 102, while FIG. ID is a block diagram illustrating further details of the cochlear implant system 102. For ease of description, FIGs. 1A-1D will generally be described together.

[0023] As noted, cochlear implant system 102 includes an external component 104 that is configured to be directly or indirectly attached to the body of the recipient and an implantable component 112 configured to be implanted in the recipient. In the examples of FIGs. 1 A-1D, the external component 104 comprises a sound processing unit 106, while the implantable component 112 includes an internal coil 114, a stimulator unit 142, and an elongate stimulating assembly 116 configured to be implanted in the recipient’s cochlea.

[0024] In the example of FIGs. 1A-1D, the sound processing unit 106 is an off-the-ear (OTE) sound processing unit, sometimes referred to herein as an OTE component, that is configured to send data and power to the implantable component 112. In general, an OTE sound processing unit is a component having a generally cylindrically shaped housing 105 and which is configured to be magnetically coupled to the recipient’s head (e.g., includes an integrated magnet configured to be magnetically coupled to a magnet in the implantable component 112). The OTE sound processing unit 106 also includes an integrated external coil 108 that is configured to be inductively coupled to the implantable coil 114.

[0025] It is to be appreciated that the OTE sound processing unit 106 is merely illustrative of the external devices that could operate with implantable component 112. For example, in alternative examples, the external component may comprise a behind-the-ear (BTE) sound processing unit or a micro-BTE sound processing unit and a separate external. In general, a BTE sound processing unit comprises a housing that is shaped to be worn on the outer ear of the recipient and is connected to the separate external coil via a cable assembly (cable), where the external coil is configured to be inductively coupled to the implantable coil 114. It is also to be appreciated that alternative external components could be located in the recipient’s ear canal, worn on the body, etc.

[0026] FIGs. 1A-1D illustrate an arrangement in which the cochlear implant system 102 includes an external component. However, it is to be appreciated that embodiments of the present invention may be implemented in cochlear implant systems having alternative arrangements. For example, embodiments presented herein can be implemented by a totally implantable cochlear implant or other totally implantable medical device. A totally implantable medical device is a device in which all components of the device are configured to be implanted under skin/tissue of a recipient. Because all components are implantable, a totally implantable medical device operates, for at least a finite period of time, without the need of an external device. An external device can be used to, for example, charge the internal power source (battery).

[0027] Returning to the specific example of FIGs. 1A-1D, FIG. ID illustrates that the OTE sound processing unit 106 comprises one or more input devices 113 that are configured to receive input signals (e.g., sound or data signals). The one or more input devices 113 include one or more sound input devices 118 (e.g., microphones, audio input ports, telecoils, efc.), one or more auxiliary input devices 119 (e.g., audio ports, such as a Direct Audio Input (DAI), data ports, such as a Universal Serial Bus (USB) port, cable port, efc.), and a wireless transmitter/receiver (transceiver) 120. However, it is to be appreciated that one or more input devices 113 may include additional types of input devices and/or less input devices (e.g., the wireless transceiver 120 and/or one or more auxiliary input devices 119 could be omitted).

[0028] The OTE sound processing unit 106 also comprises the external coil 108, a charging coil 121, a closely-coupled transmitter/receiver (transceiver) 122, sometimes referred to as or radio-frequency (RF) transceiver 122, at least one rechargeable battery 123, and a processing module 124. The processing module 124 comprises one or more processors 125 and a memory device (memory) 126 that includes alternating-polarity processing logic 128. The memory device 126 may comprise any one or more of Non-Volatile Memory (NVM), Ferroelectric Random Access Memory (FRAM), read only memory (ROM), random access memory (RAM), magnetic disk storage media devices, optical storage media devices, flash memory devices, electrical, optical, or other physical/tangible memory storage devices. The one or more processors 125 are, for example, microprocessors or microcontrollers that execute instructions for the alternating-polarity processing logic 128 stored in memory device 126 (e.g., execute instructions for implementation of the alternating-polarity focused multipolar stimulation techniques presented herein).

[0029] The implantable component 112 comprises an implant body (main module) 134, a lead region 136, and the intra-cochlear stimulating assembly 116, all configured to be implanted under the skin/tissue (tissue) 115 of the recipient. The implant body 134 generally comprises a hermetically-sealed housing 138 in which RF interface circuitry 140 and a stimulator unit 142 are disposed. The implant body 134 also includes the intemal/implantable coil 114 that is generally external to the housing 138, but which is connected to the transceiver 140 via a hermetic feedthrough (not shown in FIG. ID).

[0030] As noted, stimulating assembly 116 is configured to be at least partially implanted in the recipient’s cochlea. Stimulating assembly 116 includes a plurality of longitudinally spaced intra-cochlear electrical stimulating contacts/electrodes 144 that collectively form a contact or electrode array 146 for delivery of electrical stimulation (current) to the recipient’s cochlea.

[0031] Stimulating assembly 116 extends through an opening in the recipient’s cochlea (e.g., cochleostomy, the round window, efc.) and has a proximal end connected to stimulator unit 142 via lead region 136 and a hermetic feedthrough (not shown in FIG. ID). Lead region 136 includes a plurality of conductors (wires) that electrically couple the electrodes 144 to the stimulator unit 142. The implantable component 112 also includes an electrode outside of the cochlea, sometimes referred to as the extra-cochlear electrode (ECE) 139.

[0032] As noted, the cochlear implant system 102 includes the external coil 108 and the implantable coil 114. Generally, a magnet is fixed relative to each of the external coil 108 and the implantable coil 114. The magnets fixed relative to the external coil 108 and the implantable coil 114 facilitate the operational alignment of the external coil 108 with the implantable coil 114. This operational alignment of the coils enables the external component 104 to transmit data and power to the implantable component 112 via a closely-coupled wireless link formed between the external coil 108 with the implantable coil 114. In certain examples, the closely-coupled wireless link is a radio frequency (RF) link. However, various other types of energy transfer, such as infrared (IR), electromagnetic, capacitive and inductive transfer, may be used to transfer the power and/or data from an external component to an implantable component and, as such, FIG. ID illustrates only one example arrangement.

[0033] As noted above, sound processing unit 106 includes the processing module 124. The processing module 124 is configured to convert received input signals (received at one or more of the input devices 113) into output signals for use in stimulating a first ear of a recipient (i.e., the processing module 124 is configured to perform sound processing on input signals received at the sound processing unit 106). Stated differently, the one or more processors 125 are configured to execute alternating-polarity processing logic 128 in memory 126 to convert the received input signals into output signals 145 that represent electrical stimulation for delivery to the recipient.

[0034] As described further below, electrical stimulation signals in accordance with embodiments presented can comprise alternating-polarity focused multipolar stimulation signals. As such, the output signals 145 generated by the sound processing unit 106 represent the alternating-polarity focused multipolar stimulation signals (e.g., comprise commands/data for use by the stimulator unit 142 to form alternating-polarity focused multipolar stimulation signals). As noted elsewhere herein, the stimulator unit 142 (or possibly the alternating- polarity processing logic 128) can at least temporarily track/store the polarity characteristics/attributes of a delivered focused multipolar stimulation signal so that the opposite polarity characteristics are used to generate the next focused multipolar stimulation signal. For example, the stimulator unit 142 could store one (1) bit for each stimulation channel and use this information to determine the polarity of the next alternating-polarity focused multipolar stimulation signal delivered via the corresponding stimulation channel. This information would be stored for each stimulation channel, since the polarity alternates in relationship to stimulation signals delivered via a given stimulation channel.

[0035] As noted, FIG. ID illustrates an embodiment in which the processing module 124 in the sound processing unit 106 generates the output signals. In an alternative embodiment, the sound processing unit 106 can send less processed information (e.g., audio data) to the implantable component 112 and the sound processing operations (e.g., conversion of sounds to output signals 145) can be performed by a processor within the implantable component 112. That is, the implantable component 112, rather than the sound processing unit 106, could include a processing module that is similar to processing module 124 of FIG. ID.

[0036] Returning to the specific example of FIG. ID, the output signals 145 are provided to the RF transceiver 122, which transcutaneously transfers the output signals (e.g., in an encoded manner) to the implantable component 112 via external coil 108 and implantable coil 114. That is, the output signals are received at the RF interface circuitry 140 via implantable coil 114 and provided to the stimulator unit 142. The stimulator unit 142 is configured to utilize the output signals to generate electrical stimulation signals (e.g., current signals) for delivery to the recipient’s cochlea via stimulation channels, where each stimulating channel comprises one or more of the stimulating electrodes/contacts 144. In this way, cochlear implant system 102 electrically stimulates the recipient’s auditory nerve cells, bypassing absent or defective hair cells that normally transduce acoustic vibrations into neural activity, in a manner that causes the recipient to perceive one or more components of the received sound signals.

[0037] As noted, the processing module 124 generates the output signals 145 which, in turn, are used by the stimulator unit 142 to generate current pulses and/or electrode shorting periods that, as described below, form alternating-polarity focused multipolar stimulation signals presented herein. As such, the processing module 124 and the stimulator unit 142 are sometimes collectively referred to herein as a “stimulation subsystem” 143 that, in general, is configured to generate a plurality of alternating-polarity focused multipolar stimulation signals for delivery the plurality of electrodes 144.

[0038] In general, with electrical stimulation, the flow of anions (-) and cations (+) is controlled by the mechanics of the circuitry within the stimulator unit. In a stimulator unit, the cathode is considered the negative pole (-) because it discharges anions (-), while the anode is the positive pole (+) because it discharges cations (+). Therefore, depending on the configuration of the polarity of a stimulator at a given time, the stimulator will discharge either cations or anions into the body part being stimulated. In cathodic stimulation, anions (-) are discharged into the body as current flows from the cathode (-), through the tissue, and back to the anode (+). In anodal stimulation, cations (+) are discharged into the body as current flows from the anode (+), through the tissue, and back to the cathode (-).

[0039] In addition, electrical stimulation of the tissue (e.g., nerve cells) requires “charge balancing.” That is, any charge delivered to the recipient’s tissue must also be removed/withdrawn from the tissue, at least to a level such that there is a net average DC current flow below a predetermined threshold (e.g., approximately less than lOOnA).

[0040] As shown in FIG. 2, certain implantable medical devices use biphasic stimulation signals 247 (biphasic stimulation) to ensure charge balancing. In conventional biphasic stimulation, the device’s stimulation circuit (stimulator) delivers a first cathodic (-) current pulse 250 followed by a second anodic (+) current pulse 252 (or vice versa in alternative embodiments), where the first and second current pulses are generally “balanced.” That is, the first and second current pulses forming a biphasic stimulation signal are generally configured to inject substantially the same amount of charge, but with opposing polarities, into the tissue. [0041] For example, as shown in FIG. 2, for each biphasic stimulation signal 247, the implantable medical device generates and injects the cathodic current pulse 250 into the electrode-tissue interface. The cathodic pulse 250 depolarizes axons in the recipient’s tissue and, accordingly, triggers an action potential (e.g., with an auditory prosthesis such as cochlear implant system 102, the cathodic current pulse is the stimulating part that evokes a hearing perception).

[0042] As shown, the cathodic current pulse 250 is followed by an Inter Phase Gap (IPG) 251 (e.g., a time period in which no stimulation signals are delivered). After the IPG 251, the implantable medical device then generates and injects the anodic current pulse 252. The anodic pulse 252 injects a charge into the electrode-tissue interface to reverse the potentially damaging electrochemical processes that can occur at the electrode-tissue interface during delivery of the cathodic current pulse 250. That is, the cathodic pulse and the anodic current pulse are generally “balanced” in that they each inject similar charges (e.g., within about 5 percent of one another), but with opposite polarities, into the electrode-tissue interface. The end result is that the tissue is generally charge balanced.

[0043] As noted, the anodic current pulse 252 may be followed by a period 254 of shorting (shorting period) in which all the implantable electrodes are shorted together. In general, biphasic stimulation pulses (i.e., two sequential current pulses of opposite polarity, such as pulses 250 and 252) produce stimulation with close to zero net charge at the electrode-tissue interface (e.g., generally remove charge imbalance to a point to ensure a net average DC current flow below a predetermined threshold). As a result, the shorting period 254 is relatively short and may function as a safety mechanism. In conventional biphasic stimulation, the shorting period 254 has a predetermined length (no feedback loop).

[0044] Since the anodic current pulse 252 is configured to balance the charge injected by the cathodic current pulse 250, the anodic current pulse 252 is generated with a current source and generally requires a similar amount of energy from the implant power supply as the cathodic current pulse. That is, nearly half of the power consumed through biphasic stimulation is consumed through generation of the second polarity current pulse (e.g., the anodic current pulse 252) which merely removes charge from the tissue. Since, in biphasic stimulation the shorting period 254 is relatively short, biphasic stimulation is well suited for use with higher stimulation rate stimulation strategies/paradigms.

[0045] Almost half of the stimulation power used on biphasic stimulation can be saved by the use of monophasic stimulation in which the anodic pulse is replaced by a long electrode shorting period. That is, shown in FIG. 3 is a monophasic stimulation signals 349 where the implantable medical device (e.g., cochlear implant system 102) only generates a cathodic current pulse 350 (or only an anodic pulse in alternative embodiments) and replaces the anodic current pulse with a longer period 354 of shorting (shorting period) that immediately follows the cathodic current pulse 350. In conventional monophasic stimulation, the shorting period 354 has a predetermined length (no feedback loop) that is configured to remove all of the charge introduced by the stimulation pulse.

[0046] The advantage of monophasic stimulation is that the shorting period 354 requires no stimulation energy from the implantable medical device and, as such, stimulation power is almost halved relative to biphasic stimulation. However, the length of the shorting period 354 needs to be sufficiently long (e.g., have a time length) so as to extract the injected charge and keep the average net DC current to below a predetermined threshold, such as approximately less than lOOnA. Stated differently, the shorting period 354 has a time length that is sufficient to ensure removal of remaining charge imbalance, at least to a point to ensure a net average DC current flow below a predetermined threshold. A disadvantage of monophasic stimulation is that the time length of the shorting period 354 can be very long in order for the charge to decay to an acceptable level which, in turn limits the use of monophasic stimulation with higher stimulation rate stimulation strategies.

[0047] As described above, biphasic stimulation and monophasic stimulation each have associated advantages and disadvantages. In particular, whereas the brief shorting period makes biphasic stimulation well suited can be used with higher stimulation rate stimulation strategies/paradigms, biphasic stimulation also consumes a significant amount of power simply for the purposes of charging balancing. In addition, monophasic stimulation does not consume power for the purposes of charging balancing, the long shorting period monophasic stimulation limits the use of the monophasic stimulation with higher stimulation rate stimulation strategies. [0048] Presented herein are “alternating-polarity focused multipolar stimulation (FMP) techniques” that provide reduced power benefits in a multipolar stimulation implementation. More specifically, referring specifically to the arrangement of FIGs. 1A-1D, the cochlear implant system 102 is configured to generate “alternating-polarity focused multipolar stimulation signals (FMP)” based on one or more received sound signals. As used herein, each “alternating-polarity focused multipolar stimulation signal” is only comprised of so-called “single-polarity current pulses (single-polarity pulses)” and, as described further below, the polarity characteristics of the alternating-polarity focused multipolar stimulation signals altemate/reverse for each alternating-polarity focused multipolar stimulation signal.

[0049] As used herein, single-polarity current pulses are current pulses that each have only a single current polarity (i.e., only a cathodic current pulse or only an anodic current pulse, without any associated balancing pulse having the opposing current polarity). Since there is no second polarity pulse, there is no energy/power required to generate a second current pulse, which achieves a power savings that is similar to monophasic stimulation.

[0050] As noted above, a fundamental principle of electrical stimulation of tissue (e.g., nerve cells) is charge balancing, meaning any charge delivered to the recipient’s tissue must also be removed/withdrawn from the tissue, at least to a level such that there is a net average DC current flow below an acceptable predetermined threshold (e.g., below approximately less than lOOnA). This principle is an underlying reason why, in conventional arrangements, biphasic stimulation or monophasic stimulation is used for tissue stimulation (i.e., the current injected is immediately balanced via an opposing polarity pulse or a long shorting period that withdraws substantially all of the injected charge). The techniques presented herein, which use only single-polarity current pulses would seemingly violate these charge balancing principles. However, this is not the case as the inventors have discovered that, over time and with proper control over the size of the stimulated nerve areas, the alternating-polarity focused multipolar stimulation will achieve net average DC current flow below an acceptable predetermined threshold (e.g., below approximately less than lOOnA) without introducing stimulation artefacts.

[0051] More specifically, alternating-polarity focused multipolar stimulation is DC balanced, but also leaves a small DC potential after each stimulation pulse. However, since the polarity of successive pulses alternate (or at least are random), these cancel out over time resulting in zero net DC. The size of the DC potential left after each stimulation is also less important and the use of alternating-polarity focused multipolar stimulation can reduce the need for series capacitors (e.g., if the DC is less, the series capacitors may not be needed, as is the case with biphasic stimulation, which is not DC balanced).

[0052] In addition, as noted above, single-polarity pulses have approximately half of the stimulation power draw as biphasic pulses because there is no second polarity phase to requiring implant power. Moreover, single-polarity pulses result in lower thresholds than biphasic pulses, which can further reduce stimulation power.

[0053] The benefits of single-polarity pulses are clear and described above. However, a major drawback of single-polarity pulses, when used in monopolar stimulation, is that unwanted precepts can likely occur. Monopolar stimulation refers to a stimulation technique in which current pulses are typically delivered via one stimulation electrode generally located proximate to target nerve cells, but the current returns to stimulator/ground via one or more “remote” electrodes that are not proximate to target nerve cells, which results in a large amount of current spread between adjacent electrodes. With monopolar stimulation using single-polarity pulses, an arbitrary stimulation polarity (i.e., in phase or out of phase) between adjacent electrodes affects the current flow and hence percept of neural populations between the adjacent electrodes. Since the in phase and out of phase nature of the waveform is arbitrary, and is hard to control in a practical map, this is likely to lead to arbitrary and uncontrolled percepts for alternating-polarity monopolar stimulation. However, the percept is the same for alternating- polarity focused multipolar stimulation, regardless of the polarity leading to no perceptual difference between the two phase cases.

[0054] Stated differently, alternating single-polarity pulses can be used with focused multipolar stimulation due to fact that the focused multipolar stimulation signals each stimulate only narrow regions of nerve cells at each stimulation channel, meaning that the there is little to no overlap between the nerve cells stimulation by two adjacent stimulation channels. As such, the alternating single-polarity pulses can be either in-phase or out-of-phase as they have little impact on any overlapping nerve cell regions. In contrast, monopolar stimulation has a large amount of current spread such that two adjacent stimulation channels will stimulate overlapping nerve cell regions. As a result, with monopolar stimulation, the alternating singlepolarity pulses would need to out-of-phase, or else the overlapping nerve cells will be overstimulated leading to the arbitrary and uncontrolled percepts (e.g., at the overlapping nerve cell regions). Since the phase of the alternating single-polarity pulses, in practice, hard to control, alternating single-polarity pulse are not suited for monopolar stimulation. For example, most monopolar stimulation algorithms apply stimulation on electrodes or channels in a basal to apical sequence (because this mimics the natural behavior of the cochlea). Therefore, adjacent electrodes and channels are likely to receive two stimulation pulses close together in time, leading to the issue mentioned above. In one scenario for the monopolar case, unwanted percepts are likely to occur at a frequency that corresponds to how rapidly the two phase cases (in and out of phase) switch between phase states. This is arbitrary and potentially annoying for recipients.

[0055] In certain embodiments alternating-polarity focused multipolar stimulation signals can also include one or more additional shorting periods. However, the shorting period are reduced for alternating-polarity stimulation compared to monophasic or biphasic stimulation, perhaps even to zero in some circumstances, because alternating-polarity stimulation induces less DC in the stimulated electrodes.

[0056] Before describing further details of the alternating-polarity focused multipolar stimulation techniques presented herein, it is useful to explain some relevant terminology that will be used in the following descriptions. More specifically, certain hearing devices (e.g., cochlear implants), receive sound signals via one or more sound inputs (e.g., microphones) and a sound processor converts one or more sound signals, at a given time instance, into one or more “channel amplitudes.” Each of the one or more channel amplitudes represent the magnitude of different frequency components of the one or more sound signals at the given time instance. One or more of the channel amplitudes are converted to a corresponding focused multipolar stimulation signal that is delivered to the recipient via a corresponding “stimulation channel.”

[0057] As used herein, a “stimulation channel” is a set of electrodes with an associated set of “weights” (fixed real numbers) that are used to scale current applied via the electrodes, and a “focused multipolar stimulation signal” is the resulting current pulses that are delivered to the recipient via the stimulation channel. Stated differently, a “focused multipolar stimulation signal” is a set of current pulses applied via a stimulation channel, formed by the channel amplitudes (sounds) as scaled by the weights set for the corresponding stimulation channel.

[0058] In accordance with embodiments presented herein, each weight associated with each focused multipolar stimulation signal has a “polarity attribute.”. A weight can be described as a positive number or “amplitude” multiplied by a polarity attribute, where a polarity attribute can have a value of either negative one (-1) or positive one (+1). As used herein, the set of polarity attributes for a given focused multipolar stimulation signal refer to the polarities (positive or negative) of the real numbers (weights) used to scale the channel amplitudes when delivered via the given stimulation. As a result, the current pulses forming the given focused multipolar stimulation signal will each have a single associated polarity, but the polarity of the pulses forming a given focused multipolar stimulation signal can be different (i.e., one or more single-polarity pulses within a given focused multipolar stimulation signal can have a positive polarity and one or more single-polarity pulses within the same given focused multipolar stimulation signal can have a negative polarity).

[0059] In accordance with the alternating-polarity focused multipolar stimulation techniques presented herein, focused multipolar stimulation signals delivered via a given stimulating channel have “alternating” polarity attributes. As used herein, “alternating” polarity attributes means that any two successive focused multipolar stimulation signals use opposite polarity weights (real numbers) when delivering the current. Opposite polarity attributes are mathematically defined as the immediately prior polarity attribute multiplied by a value of negative one (-1). It is to be appreciated that is mathematical definition does not necessarily require such a step to be performed during implementation of the techniques presented herein. [0060] In view of the above, the alternating-polarity focused multipolar stimulation techniques can be explained with reference to an example first stimulation channel. In this example, a first focused multipolar stimulation signal is delivered via the first stimulation channel, where the first focused multipolar stimulation signal has a first set of polarity attributes. In accordance with the techniques presented herein, the next focused multipolar stimulation signal delivered via the first stimulation channel, referred to herein as the second focused multipolar stimulation signal, has a second set of polarity attributes that are opposite to the first set of polarity attributes (i.e., the second set of polarity attributes are, mathematically, the first set of polarity attributes multiplied by a value -1). The next focused multipolar stimulation signal delivered via the first stimulation channel, referred to herein as the third focused multipolar stimulation signal, has the set of polarity attributes that are the same as the first set of polarity attributes, but opposite polarity relative to the second set of polarity attributes (i.e., the third set of polarity attributes are, mathematically, the second set of polarity attributes multiplied by a value -1). The next focused multipolar stimulation signal delivered via the first stimulation channel, referred to herein as the fourth focused multipolar stimulation signal, has the set of polarity attributes that are the same as the second set of polarity attributes, but opposite polarity relative to the third set of polarity attributes (i.e., the fourth set of polarity attributes are, mathematically, the third set of polarity attributes multiplied by a value -1). This alternating pattern of use of the alternating polarity attributes continues indefinitely for focused multipolar stimulation signals delivered via the first stimulation channel. In operation, the device stores a value (e.g., a bit) indicating which polarity attributes should be used in generating and/or delivering a next focused multipolar stimulation signal.

[0061] FIGs. 4 and 5 are schematic diagrams illustrating example uses of the alternating- polarity focused multipolar stimulation signals, in accordance with embodiments presented herein. For ease of description, the examples of FIGs. 4 and 5 will generally be described with reference to the cochlear implant system 102 of FIGs. 1A-1D. However, as explained elsewhere herein, the alternating-polarity focused multipolar stimulation techniques can be applied in a variety of contexts and can be implemented by a number of different implantable or non-implantable medical devices, different implantable or non-implantable medical device systems, etc.

[0062] In general, FIGs. 4 and 5, each include waveforms illustrating use of alternating- polarity focused multipolar stimulation on two stimulation channels. More specifically, FIGs. 4 and 5 each illustrate the current through six (6) electrodes, referred to as electrode 1, electrode 2, electrode 3, electrode 4, electrode 5, and electrode 6, over a period of time. The six electrodes form at least two (2) overlapping stimulation channels, referred to as stimulation channel 3 (e.g., formed by electrodes 1, 2, 3, 4, and 5) and stimulation channel 4 (e.g., formed by electrodes 2, 3, 4, 5, and 6).

[0063] For ease of description, it is assumed that, in FIGs. 4 and 5, there is a current “I” through the center electrode of each channel (i.e., electrode 3 for stimulation channel 3 and electrode 4 for stimulation channel 4) within each stimulation signal/frame (i.e., at the time the current pulses are delivered via a given channel). In practice, the current magnitudes can be different in different channels and at different times, depending on the incoming sound and how it is processed.

[0064] In addition, the stimulation currents (current pulses) delivered via each electrode are shown in FIGs. 4 and 5 using the shaded bars, and the current in to/out of a particular electrode is indicated by the height of the bar. The current waveforms for channels 3 and 4 are illustrated using different shading simply for ease of identification. The shadings shown have no bearing on the waveform that would, in practice, be delivered via a particular electrode.

[0065] Referring specifically to FIG. 4, shown is an example use of alternating-polarity focused multipolar stimulation where the stimulation signals delivered via the stimulation channel 3 and stimulation channel 4 are “in phase.” In particular, shown in FIG. 4 are eight (8) focused multipolar stimulation signals/frames, referred to as focused multipolar stimulation signals 463(l)-463(4) (delivered via stimulation channel 3) and focused multipolar stimulation signals 464(l)-464(4) (delivered via stimulation channel 4). In operation, each of the focused multipolar stimulation signals 463(l)-463(4) and 464(l)-464(4) is delivered to evoke a percept (e.g., hearing percept) at the recipient (i.e., each focused multipolar stimulation signal separately depolarizes axons and triggers an action potential). That is, in the specific context of a cochlear implant, each focused multipolar stimulation signal 463(l)-463(4) and 464(1)- 464(4) is delivered to evoke perception of a different portion of sound/audio signals process by the cochlear implant. As described below, two successive focused multipolar stimulation signals delivered via the same stimulation channel (e.g., focused multipolar stimulation signals 463(1) and 463(2)) collectively form the alternating-polarity focused multipolar stimulation because the polarity attributes altemate/reverse between the two successive focused multipolar stimulation signals, as described above.

[0066] In FIG. 4, each focused multipolar stimulation signal 463(l)-463(4) and 464(l)-464(4) is comprised of only single-polarity current pulses through five electrodes, with current I in the corresponding center electrode, currents -0.51 in the two flanking electrodes, currents -0.251 in the further two flanking electrodes. As noted, these specific current values are merely illustrative and, in practice, the current magnitudes vary at different times and for different channels depending on the incoming sound and how the sound is processed. In addition, it is noted that the total intracochlear currents do not equal zero and it is assumed that some amount of current can flow to/from a remote extracochlear electrode since circuit laws require that the sum of all currents must equal zero.

[0067] As noted, each focused multipolar stimulation signal 463(l)-463(4) and 464(l)-464(4) is comprised of only single-polarity current pulses at each electrode. That is, as described above, within each focused multipolar stimulation signal, the weights (and resulting currents) associated with each electrode have only a single polarity attribute, but the polarity attributes can be different for different electrodes within a stimulation channel (i.e., one or more current pulses within a focused multipolar stimulation signal can be of one polarity attribute, while one or more other current pulses within the same focused multipolar stimulation signal can be of the opposite polarity attribute). In addition, as shown in FIG. 4, the polarity attributes alternate for two successive focused multipolar stimulation signals delivered via a given stimulation channel. This concept is described further below first with reference to stimulation channel 3, then with reference to stimulation channel 4.

[0068] More specifically, focused multipolar stimulation signal 463(1) at stimulation channel 3 has a first set of polarity attributes (i.e., the stimulation channel weights are each real numbers with polarity attributes as defined earlier such that the resulting current pulses have only a single polarity,), but focused multipolar stimulation signal 463(2) (i.e., the next focused multipolar stimulation signal delivered via stimulation channel 3) has a second set of polarity attributes that are opposite to the first set of polarity attributes (i.e., the second set of polarity attributes are, mathematically, the first set of polarity attributes multiplied by a value -1). For example, as shown in FIG. 4 the polarity attributes for electrodes 1, 2, 4, and 5 result in cathodic pulses (i.e., pulses current shown below the horizontal line) in stimulation signal 463(1), but the polarity attributes for electrodes 1, 2, 4, and 5 all result in anodic pulses (i.e. pulses shown above the horizontal line) in focused multipolar stimulation signal 463(2). Similarly, the polarity attributes for electrode 3 results in an anodic pulse in focused multipolar stimulation signal 463(1), but the polarity attributes for electrode 3 results in a cathodic pulse in focused multipolar stimulation signal 463(2).

[0069] Focused multipolar stimulation signal 463(3), which is the third focused multipolar stimulation signal delivered via stimulation channel 3, again has the first set of polarity attributes (i.e., the second set of polarity attributes multiplied by a value -1), while the fourth focused multipolar stimulation signal 463(4) delivered via stimulation channel 3 again has the second set of polarity attributes (i.e., the first set of polarity attributes multiplied by a value - 1). The alternating pattern of polarity for each successive focused multipolar stimulation signal on the same stimulation channel continues indefinitely, where the present or next set of polarity attributes, is stored by cochlear implant system 102. That is, the cochlear implant system 102 tracks the polarity of the stimulation at each stimulation channel to ensure that the next focused multipolar stimulation signal delivered via the same stimulation channel has the opposite set of polarity attributes to the immediately prior focused multipolar stimulation signal within the same given stimulation channel.

[0070] In this specific example of FIG. 4, the focused multipolar stimulation signals 464(1)- 464(4) are implemented in the same manner as the focused multipolar stimulation signal 463(l)-463(4). In particular, focused multipolar stimulation signal 464(1) has a first set of polarity attributes and multipolar stimulation signal 464(2) has a second set of polarity attributes i.e., the first set of polarity attributes multiplied by a value -1). For example, as shown in FIG. 4 the polarity attributes for electrodes 2, 3, 5, and 6 all result in cathodic pulses in stimulation signal 464(1), but the polarity attributes for electrodes 2, 3, 5, and 6 are result in anodic pulses in stimulation signal 464(2). Similarly, the polarity attribute for electrode 4 results in an anodic pulse in focused multipolar stimulation signal 464(1), but the polarity attribute for electrode 4 results in a cathodic pulse in focused multipolar stimulation signal 463(2).

[0071] Focused multipolar stimulation signal 464(3), which is the third focused multipolar stimulation signal delivered via stimulation channel 4, again has the first set of polarity attributes, and finally the fourth focused multipolar stimulation signal 464(4) again has the second set of polarity attributes. The alternating pattern of polarity for each successive focused multipolar stimulation signal on the same stimulation channel continues indefinitely, where the polarity is stored by cochlear implant system 102. That is, the cochlear implant system 102 tracks the polarity of the stimulation at the stimulation channel to ensure that the next focused multipolar stimulation signal delivered via the same stimulation channel has the opposite polarity to the immediately focused multipolar stimulation signal within the same given stimulation channel.

[0072] As noted above, FIG. 4 illustrates an example were the focused multipolar stimulation signals delivered via the stimulation channel 3 and stimulation channel 4 are “in phase.” As used herein, reference to “in phase” means that the polarity attributes of the focused multipolar stimulation signals delivered at the two channels in question are the same (e.g., the first focused multipolar stimulation signal on each of stimulation channel 3 and stimulation channel 4 have the same first set of polarity attributes, the second focused multipolar stimulation signal on each of stimulation channel 3 and stimulation channel 4 have the same second set of polarity attributes, and so on).

[0073] Referring next to FIG. 5, shown is an example use of alternating-polarity focused multipolar stimulation where the focused multipolar stimulation signals delivered via the stimulation channel 3 and stimulation channel 4 are “out phase.” Shown in FIG. 5 are eight (8) multipolar first stimulation signals/frames, referred to as focused multipolar stimulation signals 563(l)-563(4) (delivered via stimulation channel 3) and focused multipolar stimulation signals 564(l)-564(4) (delivered via stimulation channel 4). In operation, each of the focused multipolar stimulation signals 563(l)-563(4) and 564(l)-564(4) is delivered to evoke a percept (e.g., hearing percept) at the recipient (i.e., each focused multipolar stimulation signal separately depolarizes axons and triggers an action potential). For example, in the specific context of a cochlear implant, each focused multipolar stimulation signal 563(l)-563(4) and 564(l)-564(4) is delivered to evoke perception of a different portion of sound/audio signals process by the cochlear implant.

[0074] In FIG. 5, similar to the case in FIG. 4, each focused multipolar stimulation signal 563(l)-563(4) and 564(l)-564(4) is comprised of only single-polarity current pulses through five electrodes, with current I in the corresponding center electrode, currents -0.51 in the two flanking electrodes and currents -0.251 in the further two flanking electrodes. As noted, these specific current values are merely illustrative and can, in practice, vary at different times and for different channels depending on the incoming sound and how the sound is processed. In addition, it is noted that the total intracochlear currents do not equal zero and it is assumed that some current flows to/from another electrode not shown in the diagram (for example, and extracochlear electrode) since circuit laws require that the sum of all currents must equal zero. [0075] As noted, each focused multipolar stimulation signal 563(l)-563(4) and 564(l)-564(4) is comprised of only single-polarity stimulation pulses at each electrode. That is, as described above, within each focused multipolar stimulation signal, the weights (and resulting currents) associated with each electrode have only a single polarity attribute, but the polarity attribute can be different for different electrodes within a stimulating channel (i.e., one or more current pulses within a focused multipolar stimulation signal can be anodic, while one or more other current pulses within the same focused multipolar stimulation signal can be cathodic). In addition, as shown in FIG. 5, the polarity attributes alternate for two successive focused multipolar stimulation signals delivered via a given stimulation channel. This concept is described further below first with reference to stimulation channel 3, then with reference to stimulation channel 4.

[0076] More specifically, focused multipolar stimulation signal 563(1) at stimulation channel 3 has a first set of polarity attributes (i.e., the stimulation channel weights are each real numbers such that the resulting current pulses only a single polarity, either cathodic or anodic), but focused multipolar stimulation signal 563(2) (i.e., the next stimulation signal delivered via stimulation channel 3) has a second set of polarity attributes that are opposite to the first set of polarity attributes (i.e., the second set of polarity attributes are, mathematically, the first set of polarity attributes multiplied by a value -1). For example, as shown in FIG. 5 the polarity attributes for electrodes 1, 2, 4, and 5 result in cathodic pulses in stimulation signal 563(1), but the polarity attributes for electrodes 1, 2, 4, and 5 all result in anodic pulses in focused multipolar stimulation signal 563(2). Similarly, the polarity attributes for electrode 3 results in an anodic pulse in focused multipolar stimulation signal 563(1), but the polarity attributes for electrode 3 results in a cathodic pulse in focused multipolar stimulation signal 563(2).

[0077] Focused multipolar stimulation signal 563(3), which is the third focused multipolar stimulation signal delivered via stimulation channel 3, again has the first set of polarity attributes (i.e., the second set of polarity attributes multiplied by a value -1), while the fourth focused multipolar stimulation signal 563(4) delivered via stimulation channel 3 again has the second set of polarity attributes (i.e., the first set of polarity attributes multiplied by a value - 1). The alternating pattern of polarity for each successive focused multipolar stimulation signal on the same stimulation channel continues indefinitely, where the present or next set of polarity attributes, is stored by cochlear implant system 102. That is, the cochlear implant system 102 tracks the polarity of the stimulation at each stimulation channel to ensure that the next focused multipolar stimulation signal delivered via the same stimulation channel has the opposite polarity to the immediately focused multipolar stimulation signal within the same given stimulation channel.

[0078] In this specific example of FIG. 5, the focused multipolar stimulation signals 564(1)- 564(4) are opposite polarity to the focused multipolar stimulation signals 563(l)-563(4) (the so called “out of phase” condition between channels 3 and 4 as described earlier). In particular, focused multipolar stimulation signal 564(1) has the second set of polarity attributes and focused multipolar stimulation signal 564(2) has the first set of polarity attributes (i.e., the second set of polarity attributes multiplied by a value -1). For example, as shown in FIG. 5 the polarity attributes for electrodes 2, 3, 5, and 6 all result in anodic pulses in stimulation signal 564(1), but the polarity attributes for electrodes 2, 3, 5, and 6 all result in cathodic pulses in stimulation signal 564(2). Similarly, the polarity attribute for electrode 4 results in a cathodic pulse in focused multipolar stimulation signal 564(1), but the polarity attribute for electrode 4 results in an anodic pulse in focused multipolar stimulation signal 564(2).

[0079] Focused multipolar stimulation signal 564(3), which is the third focused multipolar stimulation signal delivered via stimulation channel 4, again has the second set of polarity attributes, and finally the fourth focused multipolar stimulation signal 564(4) again has the first set of polarity attributes. The alternating pattern of polarity for each successive focused multipolar stimulation signal on the same stimulation channel continues indefinitely, where the current or next polarity is stored by cochlear implant system 102. That is, the cochlear implant system 102 tracks the polarity of the stimulation at the stimulation channel to ensure that the next focused multipolar stimulation signal delivered via the same stimulation channel has the opposite polarity to the immediately focused multipolar stimulation signal within the same given stimulation channel.

[0080] A primary difference between FIG. 5 and FIG. 4 is that, whereas FIG. 4 illustrates “in phase” focused multipolar stimulation signals, FIG. 5 illustrates an example in which the focused multipolar stimulation signals delivered via the stimulation channel 3 and stimulation channel 4 are “out of phase.” As used herein, reference to “out of phase” means that the polarity attributes of the focused multipolar stimulation signals delivered at the two channels are opposite to one another (e.g., the first focused multipolar stimulation signal on stimulation channel 3 has the first set of polarity attributes, while the first focused multipolar stimulation signal on stimulation channel 4 has the second set of polarity attributes, the second focused multipolar stimulation signal on stimulation channel 3 has the second set of polarity attributes, while the second focused multipolar stimulation signal on stimulation channel 4 has the first set of polarity attributes, and so on).

[0081] As noted above, in accordance with certain embodiments presented herein, the alternating-polarity focused multipolar stimulation signals can be implemented with partial shorting (partial shorting periods) during which all the implantable electrodes 144 are “shorted” together. As used herein, reference to “shorting” of implantable electrodes, such as electrodes 144, means that the stimulation electrodes are connected together to a same low impedance (e.g., connected together internally within the implantable medical device). Since the electrodes are connected to the same low impedance, the shorting, if enabled for a sufficient period of time, dissipates any charge at the electrode-tissue interface. If implemented, the partial shorting period has a short time length that is sufficient to withdraw only part of the residual charge from the tissue-electrode interface. That is, at the end of the partial shorting period, a residual charge remains at the electrode-tissue interface.

[0082] Embodiments presented herein have been primarily described with reference to an example auditory prosthesis system, namely a cochlear implant system. However, as noted above, it is to be appreciated that the techniques presented herein may be implemented by a variety of other types of implantable medical devices (or systems that include other types of implantable medical devices) that provide a wide range of therapeutic benefits to recipients, patients, or other users. For example, the techniques presented herein may be implemented by other auditory prostheses, such as acoustic hearing aids, middle ear auditory prostheses, bone conduction devices, direct acoustic stimulators, electro-acoustic prostheses, other electrically simulating auditory prostheses (e.g., auditory brain stimulators), etc. The techniques presented herein may also be implemented by tinnitus therapy devices, vestibular devices (e.g., vestibular implants), visual devices (i.e., bionic eyes), sensors, pacemakers, drug delivery systems, defibrillators, functional electrical stimulation devices, catheters, seizure devices (e.g., devices for monitoring and/or treating epileptic events), sleep apnea devices, electroporation devices, etc.

[0083] FIG. 6 illustrates an example vestibular stimulator system 602 in accordance with embodiments presented herein. In this example, the vestibular stimulator system 602 comprises an implantable component (vestibular stimulator) 612 and an external device/component 604 (e.g., external processing device, battery charger, remote control, efc.).

[0084] The vestibular stimulator 612 comprises an implant body (main module) 634, a lead region 636, and a stimulating assembly 616, all configured to be implanted under the skin/tissue (tissue) 615 of the recipient. The implant body 634 generally comprises a hermetically-sealed housing 638 in which RF interface circuitry, one or more rechargeable batteries, one or more processors, and a stimulator unit are disposed. The implant body 634 also includes an intemal/implantable coil 614 that is generally external to the housing 638, but which is connected to the transceiver via a hermetic feedthrough (not shown).

[0085] The stimulating assembly 616 comprises a plurality of electrodes 644 disposed in a carrier member (e.g., a flexible silicone body). In this specific example, the stimulating assembly 616 comprises three (3) stimulation electrodes, referred to as stimulation electrodes 644(1), 644(2), and 644(3). The stimulation electrodes 644(1), 644(2), and 644(3) function as an electrical interface for delivery of electrical stimulation signals to the recipient’s vestibular system. In accordance with embodiments presented herein, the vestibular nerve stimulator 602 is configured to stimulate the recipient’s vestibular system using alternating-polarity focused multipolar stimulation signals, as described elsewhere herein. That is, the vestibular nerve stimulator system 602 is configured to generate and deliver alternating-polarity focused multipolar stimulation signals o the receive via the stimulation electrodes 644(1), 644(2), and/or 644(3).

[0086] The stimulating assembly 616 is configured such that a surgeon can implant the stimulating assembly adjacent the recipient’s otolith organs via, for example, the recipient’s oval window. It is to be appreciated that this specific embodiment with three stimulation electrodes is merely illustrative and that the techniques presented herein may be used with stimulating assemblies having different numbers of stimulation electrodes, stimulating assemblies having different lengths, etc.

[0087] FIG. 7 illustrates a retinal prosthesis system 701 that comprises an external device 710 configured to communicate with a retinal prosthesis 700 via signals 751. The retinal prosthesis 700 comprises an implanted processing module 725 and a retinal prosthesis sensor-stimulator 790 is positioned proximate the retina of a recipient. The external device 710 and the processing module 725 can communicate via coils 708, 714.

[0088] In an example, sensory inputs (e.g., photons entering the eye) are absorbed by a microelectronic array of the sensor-stimulator 790 that is hybridized to a glass piece 792 including, for example, an embedded array of microwires. The glass can have a curved surface that conforms to the inner radius of the retina. The sensor-stimulator 790 can include a microelectronic imaging device that can be made of thin silicon containing integrated circuitry that convert the incident photons to an electronic charge.

[0089] The processing module 725 includes an image processor 723 that is in signal communication with the sensor-stimulator 790 via, for example, a lead 788 which extends through surgical incision 789 formed in the eye wall. In other examples, processing module 725 is in wireless communication with the sensor-stimulator 790. The image processor 723 processes the input into the sensor-stimulator 790, and provides control signals back to the sensor-stimulator 790 so the device can provide an output to the optic nerve. That said, in an alternate example, the processing is executed by a component proximate to, or integrated with, the sensor-stimulator 790. The electric charge resulting from the conversion of the incident photons is converted to a proportional amount of electronic current which is input to a nearby retinal cell layer. The cells fire and a signal is sent to the optic nerve, thus inducing a sight perception.

[0090] The processing module 725 can be implanted in the recipient and function by communicating with the external device 710, such as a behind-the-ear unit, a pair of eyeglasses, etc. The external device 710 can include an external light / image capture device (e.g., located in / on a behind-the-ear device or a pair of glasses, etc.), while, as noted above, in some examples, the sensor-stimulator 790 captures light / images, which sensor-stimulator is implanted in the recipient.

[0091] In accordance with embodiments presented herein, the sensor-stimulator is configured to stimulate the recipient’s optic nerve using alternating-polarity focused multipolar stimulation signals, as described elsewhere herein. That is, the retinal prosthesis system 701 is configured to generate and deli alternating-polarity focused multipolar stimulation signals to the recipient.

[0092] FIG. 8 is a flowchart of a method 890 in accordance with embodiments presented herein. Method 890 begins at 892 where a medical device system converts input signals into a plurality of alternating-polarity focused multipolar stimulation signals. At 894, the medical device system sequentially delivers the plurality of alternating-polarity focused multipolar stimulation signals to a recipient via a first stimulation channel.

[0093] FIG. 9 is a flowchart of a method 990 in accordance with embodiments presented herein. Method 990 begins at 992 where an implantable medical device system receives input signals. At 994, the input signals are converted into a plurality of multipolar stimulation signals and, at 996, each of the plurality of multipolar stimulation signals are delivered to a recipient of the implantable medical device system using only single-polarity stimulation pulses.

[0094] As should be appreciated, while particular uses of the technology have been illustrated and discussed above, the disclosed technology can be used with a variety of devices in accordance with many examples of the technology. The above discussion is not meant to suggest that the disclosed technology is only suitable for implementation within systems akin to that illustrated in the figures. In general, additional configurations can be used to practice the processes and systems herein and/or some aspects described can be excluded without departing from the processes and systems disclosed herein.

[0095] This disclosure described some aspects of the present technology with reference to the accompanying drawings, in which only some of the possible aspects were shown. Other aspects can, however, be embodied in many different forms and should not be construed as limited to the aspects set forth herein. Rather, these aspects were provided so that this disclosure was thorough and complete and fully conveyed the scope of the possible aspects to those skilled in the art.

[0096] As should be appreciated, the various aspects (e.g., portions, components, etc.) described with respect to the figures herein are not intended to limit the systems and processes to the particular aspects described. Accordingly, additional configurations can be used to practice the methods and systems herein and/or some aspects described can be excluded without departing from the methods and systems disclosed herein.

[0097] According to certain aspects, systems and non-transitory computer readable storage media are provided. The systems are configured with hardware configured to execute operations analogous to the methods of the present disclosure. The one or more non-transitory computer readable storage media comprise instructions that, when executed by one or more processors, cause the one or more processors to execute operations analogous to the methods of the present disclosure.

[0098] Similarly, where steps of a process are disclosed, those steps are described for purposes of illustrating the present methods and systems and are not intended to limit the disclosure to a particular sequence of steps. For example, the steps can be performed in differing order, two or more steps can be performed concurrently, additional steps can be performed, and disclosed steps can be excluded without departing from the present disclosure. Further, the disclosed processes can be repeated.

[0099] Although specific aspects were described herein, the scope of the technology is not limited to those specific aspects. One skilled in the art will recognize other aspects or improvements that are within the scope of the present technology. Therefore, the specific structure, acts, or media are disclosed only as illustrative aspects. The scope of the technology is defined by the following claims and any equivalents therein.

[ooioo] It is also to be appreciated that the embodiments presented herein are not mutually exclusive and that the various embodiments may be combined with another in any of a number of different manners.

Claims

CLAIMS What is claimed is:

1. A method, comprising: converting input signals into a plurality of alternating-polarity focused multipolar stimulation signals; and sequentially delivering the plurality of alternating-polarity focused multipolar stimulation signals to a recipient via a first stimulation channel.

2. The method of claim 1, wherein each of the plurality of alternating-polarity focused multipolar stimulation signals is comprised of current pulses each having one associated polarity.

3. The method of claim 1 or 2, wherein delivering the plurality of alternating-polarity focused multipolar stimulation signals to a recipient comprises: generating a first alternating-polarity focused multipolar stimulation signal; delivering the first alternating-polarity focused multipolar stimulation signal to the recipient via a first stimulation channel, wherein the first alternating-polarity focused multipolar stimulation signal has a first set of polarity attributes; generating a second alternating-polarity focused multipolar stimulation signal; and delivering the second alternating-polarity focused multipolar stimulation signal to the recipient via the first stimulation channel, wherein in the second alternating-polarity focused multipolar stimulation signal has a second set of polarity attributes that are mathematically the same as the first set of polarity attributes multiplied by a value of negative one.

4. The method of claim 3, wherein the first alternating-polarity focused multipolar stimulation signal and the second alternating-polarity focused multipolar stimulation signal have non-equal current amplitudes.

5. The method of claim 3, wherein after delivering the second alternating-polarity focused multipolar stimulation signal to the recipient, the method further comprises: generating a third alternating-polarity focused multipolar stimulation signal; and delivering the third alternating-polarity focused multipolar stimulation signal to the recipient via the first stimulation channel, wherein the third alternating-polarity focused multipolar stimulation signal has the first set of polarity attributes.

6. The method of claim 1 or 2, further comprising: converting one or more input signals into a second plurality of alternating-polarity focused multipolar stimulation signals; and delivering the second plurality of alternating-polarity focused multipolar stimulation signals to a recipient via a second stimulation channel.

7. The method of claim 6, wherein the first stimulation channel and the second stimulation channel include one or more of the same electrodes.

8. The method of claim 1 or 2, further comprising: at least temporarily storing one or more polarity attributes associated with the first stimulation channel in association with each of the plurality of alternating-polarity focused multipolar stimulation signals.

9. The method of claim 1 or 2, wherein converting the input signals into the plurality of alternating-polarity focused multipolar stimulation signals comprises: converting one or more sound signals into the plurality of alternating-polarity focused multipolar stimulation signals.

10. The method of claim 1 or 2, further comprising: performing a partial shorting operation between two or more of the plurality of alternating-polarity focused multipolar stimulation signals.

11. A method, comprising: receiving input signals at an implantable medical device system; converting the input signals into a plurality of multipolar stimulation signals; and delivering each of the plurality of multipolar stimulation signals to a recipient of the implantable medical device system using only single-polarity stimulation pulses.

12. The method of claim 11, wherein delivering each of the plurality of multipolar stimulation signals to the recipient comprises: delivering at least a first multipolar stimulation signal and at least a second multipolar stimulation signal to the recipient via a first stimulation channel; and reversing a polarity of weights associated with the first stimulation channel between the at least first multipolar stimulation signal and the at least second multipolar stimulation signal.

13. The method of claim 12, wherein delivering each of the plurality of multipolar stimulation signals to the recipient comprises: delivering at least a third multipolar stimulation signal and at least a fourth multipolar stimulation signal to the recipient via a second stimulation channel; and reversing a polarity of weights associated with the second stimulation channel between the at least third multipolar stimulation signal and the at least fourth multipolar stimulation signal.

14. The method of claim 11, 12, or 13, wherein the first stimulation channel and the second stimulation channel comprise one or more shared electrodes.

15. The method of claim 14, wherein the at least third multipolar stimulation signal is delivered between the at least first multipolar stimulation signal and the at least second multipolar stimulation signal.

16. The method of claim 15, wherein the at least first multipolar stimulation signal and the at least third multipolar stimulation signal are in phase with one another.

17. The method of claim 15, wherein the at least first multipolar stimulation signal and the at least third multipolar stimulation signal are out of phase with one another.

18. The method of claim 12, further comprising: at least temporarily storing a polarity of the weights associated with the first stimulation channel.

19. The method of claim 11, 12, or 13, wherein the input signals are environmental signals.

20. The method of claim 19, wherein the environmental signals are sound signals.

21. The method of claim 19, wherein the environmental signals are light signals.

22. The method of claim 11, 12, or 13, wherein at least two of the plurality of multipolar stimulation signals are separated by at least one shorting period.

23. An implantable medical device system, comprising: one or more input elements configured to receive environmental signals; one or more processors configured to convert a first portion of the environmental signals into control signals representing at least a first multipolar stimulation signal, and to convert a second portion of the environmental signals into control signals representing at least a second multipolar stimulation signal; and a stimulator unit configured to generate the at least first multipolar stimulation signal and the at least second multipolar stimulation signal from the control signals, and to sequentially deliver the at least first multipolar stimulation signal and the at least second multipolar stimulation signal to a recipient of the implantable medical device via a selected stimulation channel, wherein the at least first multipolar stimulation signal and the at least second multipolar stimulation signal have opposite polarity attributes.

24. The implantable medical device system of claim 23, wherein the one or more processors or the stimulator unit is configured to store the polarity attributes of the at least first multipolar stimulation signal with respect to the selected stimulation channel.

25. The implantable medical device system of claim 23, wherein the one or more input elements comprise sound input elements, and wherein the environmental signals are sound signals.

26. The implantable medical device system of claim 23, 24, or 25, wherein the one or more processors are configured to convert a third portion of the environmental signals into control signals representing at least a third multipolar stimulation signal, and wherein the stimulator unit is configured to generate and deliver the at least third multipolar stimulation signal to the recipient via another stimulation channel at a point in time between delivery of the at least first multipolar stimulation signal and delivery of the at least second multipolar stimulation signal.

27. The implantable medical device system of claim 26, wherein the selected stimulation channel and the another stimulation channel comprise one or more of the same electrodes.

28. The implantable medical device system of claim 26, wherein the at least first multipolar stimulation signal and the at least third multipolar stimulation signal are in phase with one another.

29. The implantable medical device system of claim 23, 24, or 25, wherein the implantable medical device system is an auditory prosthesis system.

30. The implantable medical device system of claim 29, wherein the auditory prosthesis system is a cochlear implant system.

31. The implantable medical device system of claim 23, 24, or 25, wherein the implantable medical device system is a balance prosthesis system.

32. The implantable medical device system of claim 23, 24, or 25, wherein the implantable medical device system is a retinal prosthesis system.

33. One or more non-transitory computer readable storage media comprising instructions that, when executed by a processor, cause the processor to: convert at least a portion of a first sound signal into a first multipolar stimulation signal; cause a stimulator unit to deliver the first multipolar stimulation signal to a recipient via a selected stimulation channel, wherein the first multipolar stimulation signal has a first set of polarity attributes; convert a portion of at least a second sound signal into a second multipolar stimulation signal; and cause a stimulator unit to deliver the second multipolar stimulation signal to a recipient via the selected stimulation channel, wherein the second multipolar stimulation signal has a second set of polarity attributes that are opposite to the first set of polarity attributes.