Top inner ear stimulation

Abstract

The present disclosure relates to apical inner ear stimulation. The apical cochlear implant includes an apical electrode assembly in conjunction with a bottom electrode assembly. The apical cochlear implant is configured to stimulate a recipient's cochlea via the apical electrode assembly in conjunction with the bottom electrode assembly.

Description

[0001] This application is a divisional of the Chinese Invention Patent Application with international application date of April 9, 2020, national application number of 202080006341.3, and invention name of “Apical Inner Ear Stimulation”. TECHNICAL FIELD

[0002] The present invention relates generally to apical inner ear stimulation. BACKGROUND

[0003] Hearing loss, which can result from many different causes, is generally of two types, conductive and / or sensorineural. Conductive hearing loss occurs when there is some impairment in the normal mechanical pathway of the ear, e.g., due to a malformation of the ossicular chain or ear canal. Sensorineural hearing loss occurs when there is impairment in the nerve pathway from the inner ear to the brain.

[0004] Individuals with conductive hearing loss typically possess some form of residual hearing because the hair cells in the cochlea are undamaged. As such, individuals with conductive hearing loss typically receive auditory prostheses that generate motion of the cochlear fluid. Such auditory prostheses include, for example, acoustic hearing aids, bone conduction devices, and direct acoustic stimulators.

[0005] However, in many profoundly deaf individuals, the cause of their deafness is sensorineural hearing loss. Those suffering from some form of sensorineural hearing loss do not receive adequate benefit from auditory prostheses that generate mechanical motion of the cochlear fluid. Such individuals can benefit from implantable auditory prostheses that stimulate the nerve fibers of the recipient’s auditory system in other ways, e.g., electrically, optically, etc. Cochlear implants are often proposed when sensorineural hearing loss is due to the absence or destruction of cochlear hair cells that transduce acoustic signals into neural impulses. Auditory brainstem stimulators are another type of auditory prosthesis that can be proposed when a recipient experiences sensorineural hearing loss due to damage to the auditory nerve. SUMMARY

[0006] In one aspect, an apical cochlear implant is provided. The apical cochlear implant includes a basapical electrode assembly including a plurality of electrodes, wherein the basapical electrode assembly is configured to be implanted into a cochlea of a recipient via a basilar region of the cochlea; an apical electrode assembly including a plurality of apical electrodes, wherein the apical electrode assembly is sized to be implanted within an apical region of the cochlea; one or more sound input devices configured to receive a sound signal; a sound processing module configured to convert the sound signal into a stimulation control signal; and a stimulator unit configured to generate a plurality of stimulation signals based on the stimulation control signal and deliver the plurality of stimulation signals to the cochlea of the recipient via the basapical electrode assembly and the apical electrode assembly.

[0007] In another aspect, a method is provided. The method includes: receiving a sound signal at one or more sound input devices of a cochlear implant, wherein the cochlear implant includes: an apical electrode assembly including a plurality of apical electrodes and a basal electrode assembly including a second plurality of electrodes; generating a plurality of stimulation signals representative of the sound signal; directly delivering a first subset of the plurality of stimulation signals to a first frequency topological region of a cochlea via one or more of the plurality of apical electrodes, wherein the first frequency topological region is associated with an acoustic frequency below a predetermined threshold frequency; and directly delivering a second subset of the plurality of stimulation signals to a second frequency topological region of the cochlea via one or more of the second plurality of electrodes of the basal electrode assembly.

[0008] In another aspect, an apparatus is provided. The apparatus includes: a basal electrode assembly including a plurality of electrodes; and an apical electrode assembly including a plurality of apical electrodes; one or more sound input devices configured to receive a sound signal; a sound processing module configured to convert the sound signal to a stimulation control signal; and a stimulator unit configured to: generate a plurality of stimulation signals based on the stimulation control signal; directly stimulate a high frequency region of a cochlea via one or more of the plurality of electrodes of the basal electrode assembly; and directly stimulate a low frequency region of the cochlea via one or more of the plurality of apical electrodes. BRIEF DESCRIPTION OF DRAWINGS

[0009] Embodiments of the application are described herein with reference to the accompanying drawings, in which:

[0010] FIG. 1A is a partial cutaway perspective view of a cochlea in which an apical cochlear electrode assembly can be implanted;

[0011] FIG. 1B is a cross-sectional view of a turn of the cochlea of FIG. 1A

[0012] FIG. 2A is a schematic diagram illustrating an apical cochlear implant in accordance with certain embodiments presented herein;

[0013] FIG. 2B is a block diagram of the apical cochlear implant of FIG. 2A

[0014] FIG. 2C is a schematic diagram illustrating more details of the apical cochlear electrode assembly and the basal electrode assembly of FIG. 2A

[0015] FIG. 3 is a plot illustrating the variation of the cross-sectional area of an example cochlea;

[0016] ​​​FIG. 4 is a functional block diagram illustrating the operation of a sound processing module of a apical cochlear implant in accordance with certain embodiments presented herein;

[0017] FIG. 5A and FIG. 5B is a schematic diagram illustrating a focused channel configuration in accordance with certain embodiments presented herein;

[0018] FIG. 6A is a graph illustrating the threshold amplitude as a function of the apical cochlear depth relative to monopolar stimulation delivered via a basapical electrode assembly, wherein return current is drawn via an extracochlear electrode;

[0019] FIG. 6B is a graph illustrating the threshold amplitude as a function of the apical cochlear depth relative to biphasic stimulation delivered via a basapical electrode assembly, wherein return current is drawn via one or more electrodes implanted in the apical region of the cochlea;

[0020] FIG. 6C is a graph illustrating the threshold amplitude as a function of the apical cochlear depth relative to partial bipolar stimulation delivered via a basapical electrode assembly, wherein return current is drawn via one or more electrodes implanted in the apical region of the cochlea and an extracochlear electrode in accordance with certain embodiments presented herein;

[0021] FIG. 7 is a functional block of a sound processing module of a apical cochlear implant in accordance with certain embodiments presented herein for optimizing speech / sound understanding by using an apical electrode assembly;

[0022] FIG. 8 is a functional block of a sound processing module of a apical cochlear implant in accordance with certain embodiments presented herein for optimizing speech / sound understanding by using an apical electrode assembly;

[0023] FIG. 9 is a functional block of a sound processing module of a apical cochlear implant in accordance with certain embodiments presented herein for optimizing speech / sound understanding by using an apical electrode assembly;

[0024] FIG. 10 is a functional block of a sound processing module of a apical cochlear implant in accordance with certain embodiments presented herein for optimizing speech / sound understanding by using an apical electrode assembly;

[0025] FIG. 11 is a schematic diagram illustrating a pulse train in accordance with certain embodiments presented herein;

[0026] FIG. 12is a diagram illustrating a burst according to certain embodiments presented herein; and

[0027] FIG. 13 is a high-level flowchart of a method according to certain embodiments presented herein. DETAILED DESCRIPTION

[0028] The recipient's cochlea is sometimes referred to as having an "apical" or "distal" region and a "basal" or "proximal" region. For ease of description, electrode assemblies implanted via the apical region of the recipient's cochlea, configured to be implanted, or configured to be implanted, are referred to herein as "apical cochlear electrode assemblies" or more simply as "apical electrode assemblies." Additionally, again for ease of description, electrode assemblies implanted via the basal region of the recipient's cochlea, configured to be implanted, or configured to be implanted, are referred to herein as "basal cochlear electrode assemblies" or more simply as "basal electrode assemblies." Presented herein are techniques for stimulating a recipient's cochlea in conjunction with apical electrode assemblies and basal electrode assemblies.

[0029] Before describing the details of the techniques presented herein, first refer to FIGS. 1A-1B Relevant aspects of an example cochlea 140 in which an apical electrode assembly can be implanted are described. More specifically, FIG. 1A is a perspective view of the cochlea 140, partially sectioned to show the cochlea's ducts and neural fibers. FIG. 1B is a cross-sectional view of a turn of the cochlea 140.

[0030] First refer to FIG. 1A The cochlea 140 is a conical, spiral structure that includes three parallel, fluid-filled ducts or canals, collectively referred to herein as ducts 102. The ducts 102 include a tympanic duct 108 (also referred to as a tympanic scala 108), a vestibular duct 104 (also referred to as a vestibular scala 104), and a middle duct 106 (also referred to as a middle scala 106). The cochlea 140 spirals around a cochlear axis 112 several times and terminates at a cochlear apex 134.

[0031] Portions of the cochlea 140 are encased in a bony labyrinth / sac 116 and a bony endosteum 121 (e.g., a thin vascular membrane of connective tissue lining the inner surface of the bone tissue forming the medullary cavity of the bony labyrinth). Spiral ganglion cells 114 are located on the opposite medial side 120 of the cochlea 140 (as shown on the left side in FIG. 1B The spiral ligament membrane 130 is located between the lateral side 118 of the spiral tympanic duct 108 and the bony sac 116, and between the lateral side 118 of the middle scala 106 and the bony sac 116. The spiral ligament 130 also typically extends around at least a portion of the lateral side 118 of the vestibular scala 104.

[0032] The fluid in the tympanic tube 108 and the vestibular duct 104 (called perilymph) has different properties from the fluid (called endolymph) that fills the middle scala 106 and surrounds the organ of Corti 110 (organ of Corti). The tympanic tube 108 and the vestibular duct 104 together form the lymphatic space 109 of the cochlea 140. Sound entering the recipient's auricle (not shown) causes pressure changes in the cochlea 140 and thus propagates through the fluid-filled tympanic tube and vestibular duct 108, 104. As noted, the organ of Corti 110 is located on the basilar membrane 124 in the middle scala 106 and contains rows of 16,000-20,000 hair cells (not shown) protruding from its surface. Above it is the tectorial membrane 132, which moves in response to pressure changes in the fluid-filled tympanic tube and vestibular duct 108, 104. Small relative movements of the layers of the membrane 132 are sufficient to cause the hair cells in the endolymph to move, thereby causing the generation of voltage pulses, or action potentials, that propagate along associated nerve fibers 128. Nerve fibers 128 embedded within the spiral lamina 122 connect the hair cells with the spiral ganglion cells 114 that form the auditory nerve 114. Each of these nerve fibers 128 emits peripheral processes that extend toward the organ of Corti 110 and central processes that project into the auditory nerve 114. The auditory nerve 114 relays the impulses to an auditory area of ​​the brain (not shown) for processing.

[0033] The location along the basilar membrane 124 where maximum hair cell excitation occurs determines the perception of pitch and loudness according to positional theory. Due to this anatomical arrangement, the cochlea 140 is characteristically referred to as "transnasally mapped." That is, regions of the cochlea 140 toward the basal region 136 respond to high-frequency signals, while regions of the cochlea 140 toward the apical region 138 respond to low-frequency signals (i.e., a low-frequency frequency topology region and a high-frequency frequency topology region). These frequency topological properties of the cochlea 140 are exploited in cochlear implants by delivering stimulation signals within a predetermined frequency range to the region of the cochlea that is most sensitive to that particular frequency range.

[0034] Generally speaking, the basal region 136 is the portion of the cochlea 140 closest to the stapes (at FIG. 1A and FIG. 1B 134). The apical region 138 is the portion of the cochlea 140 near the cochlear apex 134. More specifically, the cochlea 140 is generally a conical spiral structure (i.e., a spiral-like shape), and the apical region 138 of the cochlea 140 is generally the posterior / final (i.e., most apical) 360 degrees of the cochlea and encompasses the region of the cochlea that is frequency-topologically associated with peripheral processes and hair cells tuned to frequencies below 0.5 kilohertz (kHz).

[0035] FIG. 2A is a schematic diagram of an example cochlear implant 100 configured to implement aspects of the technology presented herein, while FIG. 2B is a block diagram of the cochlear implant 100. FIG. 2C is a schematic diagram showing further details of a portion of the cochlear implant 100. For ease of description, the description will proceed together and with reference to implanting a portion of the cochlear implant 100 into a cochlea 140 of a recipient, FIG. 1A and FIG. 1B . FIG. 2A , FIG. 2B and FIG. 2C .

[0036] The cochlear implant 100 includes an external component 101 and an internal / implantable component 103. The external component 101 is directly or indirectly attached to the recipient’s body and generally includes an external coil 107 and a magnet (not shown in FIG. 2A ) that is generally fixed relative to the external coil 107. The external component 101 also includes one or more input elements / devices 133 for receiving input signals at a sound processing unit 113. In this example, the one or more input devices 133 include a plurality of microphones 111 (e.g., microphones placed next to the pinna of the recipient, a telecoil, etc.) configured to capture / receive acoustic / sound signals (sound) of input, one or more auxiliary input devices 129 (e.g., a telecoil, one or more audio ports such as a direct audio input (DAI), a data port such as a universal serial bus (USB) port, a cable port, etc.), and a wireless transmitter / receiver (transceiver) 135, each of which is located in, on, or near the sound processing unit 113.

[0037] The sound processing unit 113 also includes, for example, at least one battery 127, a radio frequency (RF) transceiver 131, and a processing block 149. The processing block 149 includes a plurality of elements, including a sound processing module 151. The sound processing module 151 and can be formed of one or more processors (e.g., one or more digital signal processors (DSPs), one or more uC cores, etc.), firmware, software, and the like, arranged to perform the operations described herein. That is, the sound processing module 151 can be implemented as a firmware element, partially or completely implemented with digital logic gates in one or more application specific integrated circuits (ASICs), or partially or completely implemented in software, and the like.

[0038] The implantable component 103 includes an implant body (main module) 147, a top-end electrode assembly 150, and a bottom-end electrode assembly 158, each of which is configured to be implanted beneath the recipient’s skin / tissue (tissue) 123. Since the cochlear implant 100 includes both a top-end cochlear electrode assembly 150 and a bottom-end electrode assembly 158, the cochlear implant is sometimes referred to herein as a “top-end cochlear implant” 100.

[0039] The implant body 147 generally includes a hermetically sealed housing 115 in which the RF interface circuit 125 and the stimulator unit 144 are disposed. The implant body 147 also includes an internal / implantable coil 145, which is generally external to the housing 115, but is connected to the RF interface circuit 125 via a hermetic feedthrough (not shown in FIG. 1) in the housing 115. FIG. 2B

[0040] The top-end electrode assembly 150 includes a plurality of top-end electrodes 154 disposed in a carrier member 152 (e.g., a flexible silicone body). In this particular example, the top-end electrode assembly 150 includes five (5) top-end electrodes, referred to as top-end electrodes 154(1), 154(2), 154(3), 154(4), and 154(5). Each of the top-end electrodes 154(1)-154(5) is electrically connected to the stimulator unit 144 via one or more conductive wires (not shown in FIG. 1) that extend through the lead 139. As a result, the top-end electrodes 154(1)-154(5) represent at least five different stimulation channels. It should be appreciated that this particular embodiment having five top-end electrodes is merely illustrative, and the technology presented herein can be used with other numbers of top-end electrodes implanted into the recipient’s cochlea. FIGS. 2A-2C

[0041] As described further below, the positioning of the top-end electrodes 154(1)-154(5) within the apical region 138 of the cochlea 140 enables direct stimulation of the low-frequency (apical) peri- processes of the nerve fibers 128 located in the apical region of the cochlea. In accordance with the embodiments presented herein, the cochlea 140 is generally described herein as being composed of four (4) different intervals / regions, each of which is associated with (e.g., responsive to) a different frequency topological frequency range / band. In particular, the cochlea 140 is first described herein as having a “low-frequency” region that includes peri-processes associated with low-frequency nerve fibers. As used herein, the low-frequency region of the cochlea includes peri-processes corresponding to frequencies below a predetermined threshold frequency of about 1 kilohertz (kHz) (i.e., the low-frequency region of the cochlea is a region that is generally responsive to frequencies below about 1 kHz).

[0042] ​​The cochlea 140 is also described herein as having an "ultra-low" or "very low" frequency region, which includes the peripheral processes associated with ultra-low frequency nerve fibers. As used herein, the ultra-low frequency region of the cochlea includes peripheral processes corresponding to frequencies below a predetermined threshold frequency of about 0.5 kHz (i.e., the ultra-low frequency region of the cochlea is the region that typically responds to frequencies below about 500 Hz).

[0043] The cochlea 140 is also described herein as having a "mid-frequency" region, which includes the peripheral processes associated with mid-frequency nerve fibers. As used herein, the mid-frequency region of the cochlea includes peripheral processes corresponding to frequencies above about 1 kHz but below about 2 kHz (i.e., the mid-frequency region of the cochlea is the region that typically responds to frequencies between about 1 kHz and about 2 kHz).

[0044] Finally, the cochlea 140 is described herein as having a "high-frequency" region, which includes the peripheral processes associated with high-frequency nerve fibers. As used herein, the high-frequency region of the cochlea includes peripheral processes corresponding to frequencies above about 2 kHz (i.e., the high-frequency region of the cochlea is the region that typically responds to frequencies above about 2 kHz).

[0045] According to the embodiments presented herein, the four different regions of the cochlea 140 (i.e., the ultra-low, low, mid, and high frequency regions) are not arbitrary boundaries, but are related to different physical properties, namely to different temporal precision (temporal coding ability). More specifically, it has been determined that the precision of acoustic phase locking decreases above about 1 to 2 kHz, and normal hearing acoustic pitch discrimination ability deteriorates above 2 kHz. Furthermore, for acoustic stimulation, higher "vector strength" is found at or below characteristic frequencies (CFs) of 1 kHz and 2 kHz, where higher vector strength indicates better temporal coding. For example, at a characteristic frequency of 1 kHz, the vector strength can be 0.5, while at a characteristic frequency of 2 kHz, the vector strength can be 0.1. It is reported that the vector strength decreases linearly between 1 kHz to 2 kHz, with minimal temporal coding approximately above 2 kHz.

[0046] Furthermore, the auditory nerve follows higher electrical stimulation rates at lower characteristic frequencies. For example, electrical stimulation rates greater than about 450 pps are well followed by the auditory nerve for characteristic frequencies below about 1 kHz, electrical stimulation rates of about 300 pps are well followed at characteristic frequencies of about 2 kHz, and electrical stimulation rates of about 200 pps can only be well followed at characteristic frequencies greater than about 4 kHz. Moreover, the fundamental frequencies of human voices primarily occur in the frequency topological region below 500 Hz.

[0047] Thus, as is clear from the above, the boundaries defining the ultra-low, low, mid, and high frequency regions of the cochlea 140 are not arbitrary. Rather, the boundaries defining the different regions are related to changes in the physical properties of the auditory nerve of the cochlea 140, i.e., to different temporal coding capabilities.

[0048] According to embodiments presented herein, stimulation delivered by the apical electrodes 154(1)-154(5) is sometimes referred to herein as "direct" low frequency stimulation (direct low frequency stimulation channel or low frequency electrode) because the apical electrodes 154(1)-154(5) are positioned in close proximity to the target low frequency (apical) peristyle. The placement of the electrodes relative to the apical peristyle affects the effectiveness and efficiency of the stimulation delivered (e.g., greater spacing between the electrode and the target results in greater excitation spread, etc.).

[0049] The apical cochlear electrode assembly 150 is inserted into the cochlea 140 via an apical cochlear incision 156. As used herein, a cochlear incision is a surgically created opening formed in the outer wall 142 of the cochlea 140 near (at) the apical region 138. FIG. 1A ) of the cochlea 140.

[0050] The apical cochlear electrode assembly according to embodiments presented herein, such as the apical cochlear electrode assembly 150, is specifically configured (e.g., sized and dimensioned) so as to be positioned in the apical region of the recipient's cochlea (e.g., more than 720 degrees of angular position, which corresponds to the last half turn of the cochlea). As a result, the apical cochlear electrode assembly has different physical or structural characteristics / properties than a conventional basilar electrode assembly. These different structural characteristics include, for example, smaller size (e.g., smaller cross-sectional area), different shape, different flexibility, etc., without compromising the apical structure of the cochlea.

[0051] Due to the specific structure of the apical region of the cochlea, the apical cochlear electrode assembly according to embodiments presented herein has these different structural characteristics. FIG. 3 is a graph showing how the cross-sectional area of many example cochleae varies along their length. In particular, FIG. 3 includes a horizontal (x) axis showing the angular distance (in degrees) from the base of the cochlea, and a vertical (y) axis showing the cross-sectional area of the cochlea (in square millimeters (mm 2 ). FIG. 3Also included is line 165, which represents the mean of the cross-sectional measurements taken for the plurality of example cochleae. Overall, line 165 shows that the cross-sectional area of the plurality of example cochleae, on average, decreases to approximately 50% of the cross-sectional area at 180 degrees at 720 degrees (i.e., the last half turn of the cochlea). Table 2, provided below, provides numerical values for the average cross-sectional area at different angular distances, as well as the percentage of the average cross-sectional area at different angular distances relative to the cross-sectional area at 180 degrees.

[0052]

[0053] In other words, FIG. 3 And Table 2 shows that, at least in terms of size (e.g., cross-sectional area), the apical region of a recipient’s cochlea is significantly different from the basal region of the cochlea. As a result, in order to enable insertion of an apical electrode assembly into the apical region cochlea without damaging the cochlea structure, the smaller size of the apical region of the cochlea requires that the apical electrode assembly be structurally different from traditional electrode assemblies inserted into other portions of a recipient’s cochlea (e.g., in terms of size, shape, and flexibility). For example, the cross-sectional area of an apical cochlea electrode assembly according to embodiments presented herein is significantly smaller than a basal electrode array (e.g., an apical electrode assembly can have an average cross-sectional area that is approximately less than 50% of the average cross-sectional area of a basal electrode array). Thus, traditional electrode assemblies inserted into other portions of a recipient’s cochlea are not configured for insertion into the apical region of a recipient’s cochlea (e.g., the traditional electrode assemblies do not physically fit into the apical region, would damage the apical region if attempted to be inserted therein, etc.).

[0054] Additionally, the apex is approximately 900 degrees from the base of the cochlea 140, and approximately 35 mm for some recipients. Generally, 35 mm is the average distance along the basilar membrane and even greater distances at the outer wall. Moreover, the cochlea 140 itself is a narrowing curved tube that changes abruptly as it rises vertically along its length around fragile tissue (i.e., the cochlea has turns, but it also has ups and downs, which varies from recipient to recipient).

[0055] Furthermore, due to the closed nature of the cochlea 140, insertion of a conventional cochlear implant is performed “blindly,” meaning that the surgeon cannot actually see the electrode assembly as it is inserted into the cochlea, and the surgeon relies on touch / feel and experience to place the electrode assembly correctly. As noted above, the tapering physical structure of the top region of the cochlea only adds to the difficulty. As such, reaching the apex of the cochlea with a basally inserted electrode assembly without damaging the cochlea 140 itself is a nearly impossible challenge due to these and other reasons (i.e., there is a long and challenging path from the base of the cochlea to the apex of the cochlea). Thus, conventional techniques lack the ability to directly stimulate the apical peri-stimulus.

[0056] According to the technology proposed herein, a specifically configured tip electrode assembly is inserted directly into the apical region of the cochlea. In this way, the tip electrode is positioned in close proximity to the apical periapical process and can deliver electrical stimulation directly thereto. Thus, the technology proposed herein provides the ability to directly stimulate the apical periapical process without the challenges associated with inserting an electrode array from the base of the cochlea to the apex of the cochlea.

[0057] return FIG. 2B , also shown is a bottom electrode assembly 158 implanted and / or passing through the basal region of the recipient's cochlea 140. FIGS. 2A-2C In a particular embodiment, the bottom electrode assembly 158 includes a carrier member 160 and twenty-two (22) electrodes 162, sometimes individually referred to as electrodes 162(1)-162(22). The electrodes 162(1)-162(22) are connected to the bottom electrode assembly 158 via one or more wires ( FIGS. 2A-2C 1) and are electrically connected to the stimulator unit 147. As a result, the electrodes 162(1)-162(22) represent at least 22 different stimulation channels. It should be appreciated that this particular embodiment with twenty-two electrodes is merely illustrative, and that the techniques presented herein can be used with other numbers of electrodes implanted into the cochlea of ​​a recipient.

[0058] As described above, the positioning of the apical electrodes 154(1)-154(5) within the apical region 138 of the cochlea 140 enables direct stimulation of low-frequency (apical) peripheral processes (e.g., nerve fibers below about 1 kHz) in the apical region 138. As noted above, the positioning of the apical electrodes 154(1)-154(5) relative to these target peripheral processes affects the effectiveness and efficiency of the stimulation delivered (e.g., greater spacing between the electrodes and the target nerve fibers results in greater excitation spread, etc.). In contrast, the electrodes 162(1)-162(22) of the bottom electrode assembly 158 are positioned to directly stimulate high-frequency nerve fibers (e.g., nerve fibers above 2 kHz) of the cochlea 140. As such, the stimulation delivered by the electrodes 162(1)-162(22) is sometimes referred to herein as "direct" high-frequency stimulation (direct high-frequency stimulation channels or high-frequency electrodes) because the electrodes 162(1)-162(22) are positioned in close proximity to these target high-frequency cells.

[0059] The bottom electrode assembly 158 is shown as being inserted into the cochlea 140 via the bottom cochlear incision 164. However, it should be appreciated that the bottom electrode assembly 158 can also be inserted through the circular window 161 or the oval window 163.

[0060] exist FIG. 2BAlso shown in FIG. 1 is an extra-cochlear electrode (ECE) 153 configured to be implanted within a recipient outside of the recipient's cochlea 140. In this example, the extra-cochlear electrode 153 is connected to the stimulator unit 147 via one or more leads (not shown in FIG. 1) that extend through the lead 159. FIGS. 2A-2C

[0061] The stimulator unit 147 includes stimulation circuitry 155 configured to generate stimulation (current) signals for delivery to the recipient via one or more of, e.g., the tip electrodes 154(1)-154(5), the electrodes 162(1)-162(22), etc. As described further below, the stimulation signals electrically stimulate the recipient's auditory nerve fibers in a manner that causes the recipient to perceive captured / received audio signals. Although not shown in FIG. 2, the stimulator unit 147 can also include recording circuitry configured to perform electrical measurements via electrodes implanted in or near the cochlea 140, such as via the tip electrodes 154(1)-154(5), the electrodes 162(1)-162(22), and the extra-cochlear electrode 153.

[0062] As noted, the cochlear implant 100 includes an external coil 107 and an implantable coil 145. The coils 107 and 145 are typically wire antenna coils that each include multiple turns of electrically insulated single or multi-stranded platinum or gold wire. Typically, a magnet fixed relative to each of the external coil 107 and the implantable coil 145 facilitates operational alignment of the external coil with the implantable coil. This operational alignment of the coils 107 and 145 enables the external component 101 to transfer data and possibly power to the implantable component 103 via a tightly coupled wireless link formed between the external coil 107 and the implantable coil 145. For example, the tightly 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 can be used to transfer power and / or data from the external component to the implantable component, and thus, FIG. 2B Only one example arrangement is shown.

[0063] ​As noted above, the processing block 149 includes a sound processing module 151. The sound processing module 151 (e.g., one or more processing elements implementing firmware, software, etc.) is generally configured to convert input sound signals into stimulation control signals 137 for use in stimulating the recipient's first ear (i.e., the sound processing module 151 is configured to perform sound processing on input sound signals received at the one or more input devices 133 to generate signals 137 representative of electrical stimulation for delivery to the recipient). The input sound signals that are processed and converted into stimulation control signals can be audio signals received via the microphone 111 or any other input device 133.

[0064] In FIG. 2B In embodiments, the stimulation control signals 137 are provided to the RF transceiver 131, which transcutaneously transmits the stimulation control signals 137 (e.g., in an encoded manner) to the implantable component 103 via the external coil 107 and the implantable coil 145. The control signals 137 are received at the RF interface circuit 127 via the implantable coil 145 and provided to the stimulator unit 144. The stimulator unit 144 is configured to utilize the stimulation control signals 137 to generate electrical stimulation signals (e.g., current signals) that are delivered to the recipient's cochlea via the tip electrode assembly 150 and / or the base electrode assembly 158 (as described further below). In this manner, the cochlear implant 100 electrically stimulates the recipient's auditory nerve fibers, bypassing missing or defective hair cells that would normally transduce acoustic vibrations into neural activity in a manner that causes the recipient to perceive one or more components of the input audio signals.

[0065] FIG. 2A And FIG. 2B A general arrangement is shown in which the external component 101 includes a sound processing unit 113 and a separate external coil 107. In this example, the sound processing unit 113 is a behind-the-ear (BTE) sound processing unit. However, it should be appreciated that this arrangement is merely illustrative, and the embodiments presented herein can be implemented with other external component arrangements. For example, in an alternative embodiment, the external component 101 can include an over-the-ear (OTE) sound processing unit in which the external coil, microphone, and other elements are integrated into a single housing / unit that is configured to be worn on the recipient's head.

[0066] It should also be appreciated that, FIG. 2A And FIG. 2BAn arrangement is shown in which the cochlear implant 100 includes external components. However, it should be appreciated that embodiments of the present application can be implemented in cochlear implants having alternative arrangements. For example, elements of the sound processing unit 113 (e.g., such as processing blocks 149, power sources, etc.) can be implanted in the recipient.

[0067] It will be further appreciated that individual components referenced herein, e.g., microphone 111, auxiliary input 129, processing blocks 149, etc., can be distributed across more than one prosthesis, e.g., across two cochlear implants 100, and indeed across more than one type of device, e.g., across a cochlear implant 100 and a consumer electronics device or remote control for the cochlear implant 100.

[0068] Cochlear implants have been successfully used to treat sensorineural hearing loss for many years. Traditionally, a base electrode assembly is inserted into a recipient's cochlea via an opening in the basal region of the cochlea and extends from there a certain distance into the cochlea. Base electrode assemblies of different lengths have been proposed and implanted in recipients, and thus the insertion distance of the base electrode assembly can vary. However, as noted above, due to the at least partially conical spiral structure of the cochlea (i.e., the spiral shape) and the delicate anatomy of the cochlea, the base electrode assembly has a maximum insertion distance with the distal-most electrode being in the very short apical region of the cochlea. As a result, the base electrode assembly only directly stimulates the higher frequency tonotopic region of the cochlea (e.g., higher frequency auditory nerve fibers). For example, certain studies have shown that even the topmost electrode in a standard electrode array of a base electrode assembly stimulates auditory nerve fibers with best frequencies above 2 kHz most of the time.

[0069] However, we believe that the cochlea has the best temporal precision in the frequency topographic region of the cochlea's response to low frequencies, such as frequencies below 1 kHz. As such, this low frequency region can be expected to represent information in difficult listening situations, such as speech in noise, music, etc., and can better capture binaural timing cues than the high frequency region. Conventional cochlear implants lack access to these low frequency regions, which can result in common problems with conventional cochlear implants, such as speech-in-noise difficulty, music perception and binaural timing perception, and frequency-shift perception of sound.

[0070] FIGS. 2A-2C The arrangement shown in FIG. 1C shows an enhancement to a conventional cochlear implant in which the apical electrodes 154(1)-154(5) provide the ability to directly stimulate the apical region 138 of the cochlea (e.g., the low frequency around-patch) and thus directly activate the around-patch of the cochlea 140 in response to low frequencies (e.g., around-patches associated with frequencies below 1 kHz). In FIGS. 2A-2CIn the arrangement, at the frequency topological region of the cochlea 140 that responds to high frequencies, the stimulation provided by the top electrodes 154(1)-154(5) can be combined with and supplement the stimulation from the electrodes 162(1)-162(22).

[0071] In particular, as described elsewhere herein, direct stimulation of the apical region 138 of the cochlea 140 via the apical electrodes 154(1)-154(5) is used in coordination with stimulation delivered via electrodes 162(1)-162(22). That is, the apical cochlear implant 100 (e.g., the sound processing module 151) is configured to execute / implement a "full spectrum coordinated stimulation strategy" to directly stimulate the high frequency region of the cochlea 140 (e.g., the region that maps to frequencies above 1 kHz in frequency topology) as well as the low frequency region of the cochlea 140 (e.g., the region that maps to frequencies below 1 kHz in frequency topology) in order to optimally evoke perception of received sound signals. The cochlear implant 100 is said to execute a "full spectrum coordinated stimulation strategy" because the cochlear implant can directly stimulate the high frequency region of the cochlea 140, the low frequency region of the cochlea 140, the ultra-low frequency region of the cochlea 140, and possibly directly or indirectly stimulate the mid-frequency region of the cochlea 140.

[0072] A cochlear implant according to the embodiments presented herein, which is configured to perform a full spectrum coordinated stimulation strategy that includes direct stimulation of the apical periapical process of the recipient's cochlea, can provide many benefits over cochlear implants that utilize conventional bottom electrode assemblies alone to directly stimulate only the high frequency region. These benefits can include, for example, better initial speech understanding, no or perceived reduced frequency shift, etc. It can also be expected that direct stimulation of the apical periapical process of the cochlea will have a significant impact on recipients suffering from unilateral deafness, for which frequency shift (frequency offset) is unlikely to be overcome - given the unchanging acoustic reference at the same frequency topological location in the contralateral ear. These and other benefits will be obtained by accessing the low frequency periapical processes that are associated with better time encoding. Thus, it is expected that direct stimulation of these low frequency periapical processes will help encode speech in noise and music. In addition, it is known that the low frequency pathway is important in the processing of binaural auditory time difference cues.

[0073] Due to the frequency topological mapping of the cochlea 140, different parts of the received sound signal are delivered as stimulation signals to different target locations / sites of the cochlea 140 via different stimulation channels. As used herein, a stimulation channel is formed by one or more electrodes that are used to deliver a stimulation signal (current) to the cochlea 140 at a given time instance, thereby inducing stimulation at a specific target location / site of the cochlea. Therefore, FIGS. 2A-2CApical cochlear implant 100 includes low frequency (apical) stimulation channels provided by apical electrodes 154(1)-154(5), as well as high frequency (basal) stimulation channels provided by electrodes 162(1)-162(22). The stimulation channels can be formed by a single electrode or multiple electrodes that operate together to deliver stimulation to the recipient. As such, apical electrodes 154(1)-154(5) and electrodes 162(1)-162(22) can be used together to form different numbers of stimulation channels.

[0074] According to embodiments presented herein, full-spectrum coordinated stimulation strategies can be implemented in a variety of different ways to leverage different stimulation channels in a manner that optimizes speech understanding for a particular recipient. Provided below are further details regarding embodiments of full-spectrum coordinated stimulation strategies that can be implemented according to examples presented herein.

[0075] Referring first to FIG. 4 , a functional block diagram of a signal processing path 166 of a cochlear implant, such as cochlear implant 100, is shown in accordance with embodiments presented herein. As noted, apical cochlear implant 100 includes one or more input devices 133. In FIG. 4 the example, the one or more input devices include two microphones 111 and at least one auxiliary input 119 (e.g., an audio input port, a cable port, a telecoil, etc.). If not already in electrical form, sound input devices 133 convert received / input sound signals into electrical signals 167 (referred to herein as electrical input signals) that represent the received sound signals. As FIG. 4 indicated, electrical input signals 167 are provided to a pre-filter bank processing module 168.

[0076] Pre-filter bank processing module 168 is configured to combine electrical input signals 167 received from sound input devices 133 as needed, and prepare these signals for subsequent processing. Pre-filter bank processing module 168 then generates pre-filtered output signals 169, which are the basis for further processing operations as further described below. Pre-filtered output signals 169 represent the collective sound signals received at sound input devices 133 at a given point in time.

[0077] Apical cochlear implant 100 is generally configured to perform sound processing and encoding to convert pre-filtered output signals 169 into stimulation control signals 137 that represent electrical stimulation for delivery to the recipient via apical electrode assembly 150 and / or basal electrode assembly 158. As such, sound processing path 166 includes a filter bank module (filter bank) 170, a post-filter bank processing module 172, a channel selection module 174, and a channel mapping and encoding module 176.

[0078] In operation, the pre-filtered output signal 169 generated by the pre-filter bank processing module 168 is provided to the filter bank module 170. The filter bank module 170 generates a suitable set of bandwidth limited channels or frequency bins, each comprising a spectral component of the received sound signal. That is, the filter bank module 170 includes a plurality of bandpass filters that separate (bandpass filter) the pre-filtered output signal 169 into a plurality of components / channels (bandwidth limited channels), each carrying a single frequency sub-band of the original signal (i.e., a frequency component of the received sound signal).

[0079] The channels created by the filter bank module 170 are sometimes referred to herein as sound processing channels, and the sound signal components within each of the sound processing channels are sometimes referred to herein as bandpass filtered signals or channelized signals. The bandpass filtered or channelized signals created by the filter bank module 170 are processed (e.g., modified / adjusted) as they pass through the sound processing path 166. As such, the bandpass filtered or channelized signals are variously referenced at various stages of the sound processing path 166. However, it should be appreciated that references herein to bandpass filtered signals or channelized signals can refer to spectral components of the received sound signal at any point (e.g., pre-processing, processing, selection, etc.) within the sound processing path 166.

[0080] As noted above, the apical cochlear implant 100 is characterized in that stimulation signals can be delivered via the apical electrodes 154(1)-154(5) and / or via the electrodes 162(1)-162(22). The presence of the apical electrodes 154(1)-154(5) that can directly stimulate the apical region 138 can introduce variations into the bandpass filtering process relative to cochlear implants that utilize only a traditional basal electrode assembly.

[0081] For example, the filter bank module 170 can include bandpass filters corresponding to low frequencies (e.g., below 1 kHz) that have varying spectral widths and / or spectral widths that are different than (i.e., narrower in spectrum than) the spectral widths of the bandpass filters corresponding to high frequencies. In other words, the filter bank module 170 can include bandpass filters (e.g., implemented as part of a Fast Fourier Transform (FFT)) having different or variable spectral widths such that the resulting bandwidth limited channels have different or variable spectral widths. For example, the spectral width of a bandwidth limited channel associated with low frequencies of the cochlea can be narrower than the spectral width of a bandwidth limited channel associated with high frequencies of the cochlea (e.g., the bandwidth limited channel corresponding to low frequencies has a narrower spectral width than the bandwidth limited channel corresponding to high frequencies of the sound signal). In certain embodiments, the spectral widths of the bandpass filters of the filter bank module 170 can depend on the associated frequency topological location of the cochlea 140 (e.g., the bandwidth limited channel corresponding to low frequencies has a narrower spectral width than the bandwidth limited channel corresponding to high frequencies of the sound signal). Thus, the filter bank module 170 is configured to bandpass filter the received sound signal with a plurality of bandpass filters to generate a set of bandwidth limited channels, each channel including spectral components of the received sound signal. In certain embodiments, the plurality of bandpass filters have non-uniform spectral widths.

[0082] The use of spectrally narrower bandpass filters for low frequencies FIG. 4 The arrangement of the's can facilitate the delivery of more acoustic information / detail at the apical region 138, which is most critical for speech / sound perception. Similarly, the use of spectrally wider bandpass filters for high frequencies enables the cochlear implant 100 to deliver less acoustic detail in other regions of the cochlea 140, where the acoustic detail can not be needed and / or is not critical for sound perception.

[0083] Returning to FIG. 4 At the output of the filter bank module 170, the channelized signal is initially referred to herein as a pre-processed channelized signal 171. The number of channels "m" and the pre-processed channelized signal 171 generated by the filter bank module 170 can depend on a number of different factors, including but not limited to implant design, number of active electrodes, coding strategy, and / or recipient preference(s).

[0084] The pre-processed channelized signal 171 is provided to a post-filter bank processing module 172. The post-filter bank processing module 172 is configured to perform a number of sound processing operations on the pre-processed channelized signal 171. These sound processing operations include, for example, channelized gain adjustments (e.g., gain adjustments to one or more discrete frequency ranges of the sound signal) in one or more channels for hearing loss compensation, noise reduction operations, speech enhancement operations, and so on. After performing the sound processing operations, the post-filter bank processing module 172 outputs a plurality of processed channelized signals 173.

[0085] In FIG. 4 particular arrangements of FIG. 4 the channel selection module 174 selects a subset "n" of the "m" processed channelized signals 173 for use in the generation of electrical stimulation for delivery to the recipient (i.e., the sound processing channel count is reduced from "m" channels to "n" channels). In one particular example, the "n" largest amplitude channels (maxima) are derived from the "m" available combined channel signals / masking signals, where "m" and "n" are programmable during initial fitting and / or operation of the prosthesis. It should be appreciated that different channel selection methods can be used and are not limited to maxima selection.

[0086] In FIG. 4 embodiments of

[0087] It should also be appreciated that in certain embodiments, the channel selection module 174 can be omitted. For example, certain arrangements can use continuous interleaved sampling (CIS), CIS-based hybrid of channel selection and F0 derivation coding, or other non-channel selection sound coding strategies.

[0088] The sound processing path 166 also includes a channel mapping module 176. The channel mapping module 176 is configured to map the amplitudes of the selected signal 175 (or the processed channelized signals 173 in embodiments that do not include channel selection) to a set of stimulation control signals (e.g., stimulation commands) 137 that represent the properties of the electrical stimulation signals to be delivered to the recipient in order to evoke a perception of at least a portion of the received sound signal. This channel mapping can include, for example, threshold and comfort level mapping, dynamic range adjustment (e.g., compression), volume adjustment, and so on, and can encompass the selection of various sequential and / or simultaneous stimulation strategies.

[0089] InFIG. 4 In an embodiment, a set of stimulation commands representing electrical stimulation signals are encoded for transcutaneous transmission (eg, via an RF link) to the implantable component 104 ( FIG. 1A and FIG. 1B ).exist FIG. 4 In the specific example of , the encoding is performed at the channel mapping module 176. As such, the channel mapping module 176 is sometimes referred to herein as a channel mapping and encoding module and operates as an output block configured to convert the plurality of channelized signals into the plurality of stimulus control signals 137.

[0090] As noted above, the apical cochlear implant 100 implementing a full spectrum coordinated stimulation strategy according to embodiments presented herein can exploit direct access to peripheral processes (particularly in the apical region 138) through the use of filters of varying spectral bandwidths at the filter bank module 170. In some embodiments, the apical cochlear implant 100 can also or alternatively exploit direct access to peripheral processes of the apical region 138 through a physical electrode spacing in the apical electrode assembly 150 that is different than the physical electrode spacing in the basal electrode assembly 158 (e.g., electrodes 154(1)-154(5) having a smaller spacing than electrodes 162(1)-162(26)).

[0091] Additionally or alternatively, the apical cochlear implant 100 can exploit direct access to peripheral processes in the apical region 138 by using various stimulation resolutions (eg, using different electrode configurations).

[0092] Electrical stimulation of nerve cells operates by causing excitation / activation of selected groups of nerve cells. In order for nerve cells to excite, the nerve cells must first obtain a membrane voltage that is higher than a critical threshold. The number of nerve cells excited in response to electrical stimulation affects the "resolution" of the electrical stimulation. As used herein, the resolution of electrical stimulation or "stimulation resolution" refers to the amount of acoustic detail (i.e., the spectrum and / or temporal details from (one or more) input acoustic sound signals) delivered by the implanted electrodes in the cochlea and then received by the primary auditory neurons (spiral ganglion cells). As further described below, electrical stimulation has many characteristics / attributes that control the resolution of the stimulation. These attributes include, for example, the spatial attributes of the electrical stimulation, the temporal attributes of the electrical stimulation, the instantaneous spectral bandwidth attributes of the electrical stimulation, and the like.

[0093] The spatial properties of electrical stimulation control the width of the region of activated neural cells along the frequency axis (i.e., along the basilar membrane) in response to the delivered stimulation, and are sometimes referred to herein as the "spatial resolution" of the electrical stimulation. The temporal properties refer to the temporal encoding of the electrical stimulation, such as the pulse frequency, and are sometimes referred to herein as the "temporal resolution" of the electrical stimulation. The instantaneous spectral bandwidth property refers to the proportion of the analyzed spectrum delivered via the electrical stimulation, such as the number of channels stimulated out of the total number of channels in each stimulation frame.

[0094] The spatial resolution of electrical stimulation can be improved, for example, by using different electrode configurations for a given stimulation channel to activate regions of nerve cells of different widths. For example, monopolar stimulation is an electrode configuration in which, for a given stimulation channel, current is "sourced" via one of the electrodes within the cochlea, but current is "sourced" via the extracochlear electrodes, such as 153 ( FIG. 1A ) is “sunk” by far-field electrodes such as . Monopolar stimulation typically exhibits a large degree of current spreading (i.e., a wide stimulation pattern) and, therefore, has low spatial resolution. Other types of electrode configurations, such as bipolar, tripolar, focused multipolar (FMP) (also known as “phased array” stimulation), etc., typically reduce the size of the stimulated neural population by “providing” current via one or more electrodes within the cochlea, while also “sunk” current via one or more other electrodes that are close to (or adjacent to) the current-providing electrode. Bipolar, tripolar, focused multipolar and other types of electrode configurations that provide and sink current via electrodes are generally and collectively referred to herein as “focused” stimulation. Focused stimulation typically exhibits a smaller degree of current spreading (i.e., a narrow stimulation pattern) than monopolar stimulation and, therefore, has a higher spatial resolution than monopolar stimulation. Similarly, other types of electrode configurations, such as two-electrode modes, virtual channels, wide channels, defocused multipolar, etc., typically increase the size of the stimulated neural population by “providing” current via multiple adjacent electrodes.

[0095] Again, as noted, the apical cochlear implant 100 can exploit direct access to the surrounding processes in the apical region 138 by using various stimulation resolutions. For example, in certain embodiments presented herein, the apical cochlear implant 100 can use focused stimulation within the apical region 138 so that stimulation signals delivered via the apical electrodes 154(1)-154(5) stimulate only a narrow region of neurons, thereby minimizing overlap in the resulting neural responses from adjacent stimulation channels. This strategy can better mimic natural hearing and enable better perception of detail in the sound signal (i.e., better control of the current to produce discernible pitch).

[0096] FIG. 5A and FIG. 5BA focused channel configuration is shown in which in-ear compensation currents are added to reduce the spread of the current along the frequency axis of the cochlea (i.e., one or more of the apical electrodes provide / deliver current and one or more of the apical electrodes return / draw current). The polarity of the delivered compensation current is opposite to the polarity of the primary / current. Generally, the more compensation current at nearby electrodes, the more focused the resulting stimulation pattern (i.e., the less the width of the stimulation pattern is increased, and thus the higher the spatial resolution). That is, spatial resolution is increased by introducing increasing amounts of compensation current on the electrodes surrounding the center electrode with positive current.

[0097] More specifically, in FIG. 5A , a positive stimulation current 178(A) is delivered via electrode 154(3), and a stimulation current 180(A) of opposite polarity is delivered via adjacent electrodes, i.e., electrodes 154(1), 154(2), 154(4), and 154(5). The in-ear stimulation currents 178(A) and 180(A) generate a stimulation pattern 181(A), as shown, which is spread only over electrodes 154(2)-154(4). In FIG. 5B , a positive stimulation current 178(B) is delivered via electrode 154(B), while a stimulation current 179(B) of opposite polarity is delivered via adjacent electrodes 154(2) and 154(4), and a second stimulation current 180(B) of opposite polarity is also delivered via electrodes 154(1) and 154(5). The stimulation currents 178(B), 179(B), and 180(B) generate a stimulation pattern 181(B), as shown, which is generally located in the spatial region adjacent to electrode 154(3).

[0098] FIG. 5A And FIG. 5B the difference in the stimulation patterns 181(A) and 181(B) in and, respectively, is due to the magnitude (i.e., weighting) of the opposite polarity currents delivered via adjacent electrodes 154(1), 154(2), 154(3), and 154(4). In particular, FIG. 5A A partially focused configuration is shown in which the compensation current does not completely cancel the primary current on the center electrode, and the remaining current goes to far field extra-cochlear electrodes (not shown). FIG. 5B is a fully focused configuration in which the compensation current completely cancels the primary current on the center electrode 154(4) (i.e., no far field extra-cochlear electrodes are needed). It should be appreciated that in FIG. 5A and FIG. 5B the two focused stimulation patterns shown in and, respectively, are merely illustrative, and as noted above, the focused stimulation delivered via apical electrodes 154(1)-154(5) can take many different arrangements.

[0099] According to embodiments presented herein, the use of focused stimulation in apical region 138 (e.g., delivered via apical electrodes 154(1)-154(5)) can be combined with focused stimulation being delivered to high frequency regions of cochlea 140 (e.g., via electrodes 162(1)-162(22)). Alternatively, the use of focused stimulation in apical region 138 (e.g., delivered via apical electrodes 154(1)-154(5)) can be combined with diffuse or monopolar stimulation being delivered to high frequency regions of cochlea 140 (e.g., via electrodes 162(1)-162(22)). Thus, according to embodiments presented herein, apical cochlear implant 100 can be configured to employ different electrode configurations at each of apical electrode assembly 150 and basal electrode assembly 158 (e.g., one electrode configuration for a direct low frequency stimulation channel and another different electrode configuration for a direct high frequency stimulation channel).

[0100] It will be appreciated that, in addition to or as an alternative to focused stimulation, and for current steering, apical electrodes 154(1)-154(5) can use non-focused electrode configurations. For example, in certain embodiments, apical electrodes 154(1)-154(5) can each operate as independent stimulation channels to stimulate portions of apical region 138. In these embodiments, one or more of electrodes 162(1)-162(22) and / or extra-cochlear electrode 153 can be used as a current return electrode.

[0101] As noted, increased spatial resolution is one technique that can be employed by apical cochlear implant 100 for delivering stimulation signals to apical region 138. In further embodiments, apical cochlear implant 100 can utilize different temporal resolutions (e.g., different pulse rates) at each of apical electrode assembly 150 and basal electrode assembly 158 (e.g., one pulse rate for a direct low frequency stimulation channel and another different pulse rate for a direct high frequency stimulation channel).

[0102] In a conventional cochlear implant having only a basal electrode assembly, monopolar stimulation includes delivering a current signal via one of the electrodes. Current is then drawn / returned via an extra-cochlear electrode. According to certain embodiments presented herein, apical electrodes 154(1)-154(5) can be used as current returns (current draws) for electrical stimulation being delivered via electrodes 162(1)-162(22) of basal electrode assembly 158. The use of electrodes 154(1)-154(5) as current returns can sharpen monopolar stimulation via a given electrode 162(1)-162(22).

[0103] More specifically, FIG. 6Ais a plot 682(A) in which the vertical (y) axis shows the threshold amplitude (in dB re 2000 μA) and the horizontal (x) axis shows the angular cochlear depth (in degrees), where zero degrees corresponds to the location of the round window. FIG. 6A Also included are six (6) traces showing the threshold amplitude of monopolar stimulation delivered via each of the electrodes in a standard electrode assembly (i.e., where the electrodes are located in the high frequency region of the cochlea). In FIG. 6A , trace EL1 corresponds to the most basal / proximal electrode, while trace EL22 corresponds to the most apical / distal electrode. In FIG. 6A , all of the stimulating current is drawn via the extra-cochlear electrodes. As can be seen in FIG. 6A , drawing all of the current via the extra-cochlear electrodes results in a most apical response at approximately 440 degrees, and a relatively broad response (e.g., the evoked spread evokes a wide range of nerve fibers).

[0104] FIG. 6B is a plot 682(B) in which, similar to FIG. 6A , the vertical axis shows the threshold amplitude, while the horizontal axis shows the angular cochlear depth in degrees. FIG. 6B shows an apical cochlear implant arrangement that includes a basal electrode assembly having a plurality of electrodes placed in the high frequency portion of the cochlea, and an apical electrode assembly having a plurality of electrodes placed in the frequency portion of the cochlea (i.e., the portion below 1000 kHz).

[0105] FIG. 6B Also included are six (6) traces showing the threshold amplitude of biphasic stimulation delivered via the electrodes of the basal electrode assembly. Again, trace EL1 corresponds to the most basal / proximal electrode, while trace EL22 corresponds to the most apical / distal electrode. In FIG. 6B , all of the stimulating current delivered via the basal electrode assembly is drawn via one or more of the electrodes of the apical electrode assembly (i.e., the electrodes located in the low frequency portion of the cochlea).

[0106] As can be seen in FIG. 6B , drawing the return current in this manner results in a sharper (narrower) result than the monopolar arrangement of FIG. 6A (e.g., the evoked spread evokes a smaller range of nerve fibers than FIG. 6A ), but a large number of neurons at the apex are activated at 4 dB re 200 μA. FIG. 6B Also shown is an undesirable second site of stimulation (e.g., at approximately 750 degrees), sometimes referred to as a diplophonic pitch perception.

[0107] FIG. 6C is a plot 682(C) in which, similar toFIG. 6A The vertical axis shows the threshold amplitude, while the horizontal axis shows the angular cochlear depth in degrees. FIG. 6C A top-end cochlear implant arrangement is shown that includes a bottom-end electrode assembly having a plurality of electrodes placed in a high frequency portion of the cochlea, and a top-end electrode assembly having a plurality of electrodes placed in a frequency portion of the cochlea (i.e., the portion below 1000 kHz).

[0108] FIG. 6C Also included are six (6) traces showing the threshold amplitude of a partial bipolar stimulation delivered via the electrodes of the bottom-end electrode assembly. Again, trace EL1 corresponds to the bottom-most / proximal electrode, while trace EL22 corresponds to the top-most / distal electrode. In FIG. 6C , a portion of the stimulation current is drawn via the extra-cochlear electrode, while another portion is drawn by one or more of the electrodes of the top-end electrode assembly (i.e., the electrodes located in the low frequency portion of the cochlea). In particular, the current return is split substantially between the extra-cochlear electrode and the one or more of the electrodes of the top-end electrode assembly (e.g., +1.0 current is delivered via the bottom-end electrode assembly, the extra-cochlear electrode receives / draws -0.5 and the one or more of the electrodes of the top-end electrode assembly receives / draws -0.5). As can be seen in FIG. 6C , this splitting of the return current in this manner results in a higher threshold than the monopolar arrangement of FIG. 6A . In addition, the response is narrower than those of FIG. 6A (e.g., the evoked dispersion evokes a smaller range of nerve fibers than FIG. 6A ), but not as narrow as those in FIG. 6B . In other words, FIG. 6C shows a sharpened response without producing the undesirable bipolar pitch perception.

[0109] FIGS. 6A-6CCollectively, it is shown that splitting between current return (e.g., relative amount of current drawn therefrom) among the cochlear extra-electrode and one or more of the apical electrodes can optimize / shaping the evoked pattern induced by the basapical stimulation channel. The amount of current returned / drawn via the cochlear extra-electrode and each of the one or more apical electrodes can be adjusted, for example, during a fitting session based on recipient-specific attributes. The amount of current returned / drawn via the cochlear extra-electrode and each of the one or more apical electrodes can also be different for different electrodes in the basapical electrode assembly, and the optimal proportion can be a variable that varies with electrode location. For example, more basapical electrodes can require a larger proportion of current through the apical electrodes of the apical electrode assembly to achieve the desired frequency response shift. More apical electrodes of the basapical electrode assembly can require a lower proportion of current through the apical electrodes of the apical electrode assembly as they are closer to the apex and thus more sensitive to current there.

[0110] As noted above, the full-spectrum coordinated stimulation strategy in accordance with the embodiments presented herein can be implemented in a number of different ways. In certain examples, the full-spectrum coordinated stimulation strategy can include a specific sound encoding technique to optimize speech / sound understanding through the use of the apical electrode assembly. FIGS. 7-12 More details of an example sound encoding technique are shown that utilizes the placement of the apical electrodes to directly stimulate the apical region (i.e., in conjunction with stimulation via the electrodes of the basapical electrode assembly, electrically stimulating the low frequency periphery via the apical electrodes of the apical electrode assembly to utilize apical placement and direct low frequency channel).

[0111] Referring first to FIG. 7 , a functional block of a sound processing module 751 of an apical cochlear implant is shown for optimizing speech / sound understanding through the use of the apical electrode assembly. The sound processing module 751 is configured to perform a fundamental frequency (F0) imparting / encoding process to provide enhanced pitch cues within a stimulation signal delivered to the apical periphery of the cochlear implant via the apical electrodes of the apical electrode array (i.e., adjust an initial stimulation strategy based on the fundamental frequency and channel energy to provide enhanced pitch cues at the apical stimulation channel).

[0112] It will be appreciated that FIG. 7 such logical arrangement is merely illustrative, and FIG. 7 the operations represented in FIG. 7 may be performed in a number of different ways and can be split over different functional elements and in certain examples over different devices. It will also be appreciated that the sound processing module 751 can perform other operations that have been omitted from

[0113] InFIG. 7 In embodiments of the sound processing module 751, among other elements, includes a fundamental frequency (F0) extractor 782, a pitch amplitude function 784, a channel energy detector 786, a strategy determination module 788, an F0 application module 790, and an arbiter 792. As described further below, FIG. 7 An embodiment is shown in which F0 extraction and energy detection are used to adjust the initial / primary stimulation strategy.

[0114] More specifically, in the example of FIG. 7, the sound processing module 751 receives a pre-processed channelized signal 771 (e.g., similar to the pre-processed channelized signal 171 generated by the filter bank module 170 in FIG. 1). The pre-processed channelized signal 771 is provided to the F0 extractor 782, the channel energy detector 786, and the strategy determination module 788. Although the operations are described with reference to using the processed channelized signal 771, it should also be appreciated that the operations can be performed at least in part using other versions of the received sound signal (e.g., an electrical input signal received from a sound input, a pre-filtered output signal, etc.). FIG. 7 FIG. 4 The pre-processed channelized signal 771 is provided to the F0 extractor 782, the channel energy detector 786, and the strategy determination module 788. Although the operations are described with reference to using the processed channelized signal 771, it should also be appreciated that the operations can be performed at least in part using other versions of the received sound signal (e.g., an electrical input signal received from a sound input, a pre-filtered output signal, etc.). FIG. 7 The F0 extractor 782 is configured to extract the fundamental frequency (F0) of the received sound signal (i.e., the signal used to generate the processed channelized signal 771). The output of the F0 extractor 782 is the fundamental frequency 783 and a measure of the confidence 785 that the fundamental frequency is present. The measure 785 (sometimes referred to as "pitch salience") provides an indication of the harmonicity of the received sound signal. The fundamental frequency limit (F0_limit) can be specified by characterizing the impulse following ability (e.g., psychoacoustic, electrophysiological, etc.) of the recipient. For example, the fundamental frequency limit can be 500 Hz, although this value is merely illustrative.

[0115] The fundamental frequency 783 and the pitch salience 785 are provided to the pitch amplitude function 784. The pitch amplitude function 784 is configured to determine whether the fundamental frequency 783 is a correct estimate or likelihood (i.e., determine how tonal-like the signal in the lowest frequency bin is). The pitch amplitude function 784 outputs a pitch amplitude 787. In certain examples, the pitch amplitude 787 is a function of (based on) the pitch salience (e.g., a step function if the pitch salience crosses a certain level, or a sigmoidal function for a gradual application). Alternatively, the pitch amplitude 787 is a function of the pitch salience and the fundamental frequency (e.g., including a multiple of a negative sigmoidal function of F0 such that the pitch amplitude weakens as F0 rises above F0_limit).

[0116]

[0117] ​​As noted, the pre-processed channelized signal 771 is provided to a channel energy detector 786. The channel energy detector 786 is configured to determine the energy in the lowest frequency channel, regardless of whether the signal is harmonic / regular, and output a pitch channel energy (PCE) 789. In one example, the channel energy detector 786 extracts the energy in the wideband signal (e.g., the electrical input signal 167 received from the sound input device 133 or the pre-filtered output signal 169) to drive the apical stimulation channel(s) (i.e., the F0 application electrode(s) placed around the apex). In another example, the channel energy detector 786 extracts only the energy in the low frequency range / band (e.g., below 800 Hz). The low frequency range can be adjusted to match the frequency tonotopy and determine the appropriate frequency breakpoints on a per recipient basis, for example, by measuring the acoustic pitch in the contralateral ear related to the apical electrode and the next electrode.

[0118] The F0 application module 790 receives the pitch amplitude 787, the fundamental frequency 783, and the pitch channel energy 789. The F0 application module 790 is configured to analyze these values and determine pulse control parameters 791 (e.g., pulse amplitude and timing) to encode the fundamental frequency. FIG. 8 and FIG. 9 Further details of two example implementations of the F0 application module 790 are provided.

[0119] The strategy determination module 788 is configured to generate pulse control parameters 793 (e.g., pulse amplitude and amplitude timing) according to an initial predetermined / preset strategy. That is, the strategy determination module 788 uses the initial strategy to determine the pulse control parameters 793 that are configured to apply sound information included in the received sound signal other than the fundamental frequency information. The initial strategy used to generate the pulse control parameters 793 can be, for example, a continuous interleaved sampling (CIS) strategy, a high-level combined encoder (ACE) strategy, a 500 pps strategy, and the like. In certain examples, a lower update rate strategy can be used that will supplement the F0 application electrodes.

[0120] Pulse control parameters 791 encoding the fundamental frequency are provided to an arbitrator 792. In addition to these pulse control parameters 791, the arbitrator 792 receives pulse control parameters 793 from a strategy determination module 788. The arbitrator 792 analyzes the pulse control parameters 791 and the pulse control parameters 793 to generate a stimulation control signal 737 representing electrical stimulation for delivery to the recipient via the apical electrode assembly and / or the basal electrode assembly of the cochlear implant. In certain examples, the F0 application electrode(s) (e.g., one or more apical electrodes implanted in the apical region) will have a high weight in the arbitration decision. In certain embodiments, lower amplitude of pulse energy on the lowest frequency (pitch) channel can reduce the arbitration weight, but generally it will take more control relative to other channels. That is, the arbitration decision can be configured to be faithful to the low frequency timing, so when the arbitration process determines the stimulation control signal 737, the arbitration process favors the low frequency channel.

[0121] FIG. 8 is a functional block diagram illustrating further details of one example embodiment of an F0 application module in accordance with the embodiments presented herein. In FIG. 8 the example, the pulse rate is used to apply / encode the fundamental frequency in the low frequency stimulation signal.

[0122] More specifically, the functional blocks of a sound processing module 851 for optimizing speech / sound understanding by using the apical electrode assembly are illustrated in FIG. 8 It will be appreciated that FIG. 8 this logical arrangement is merely illustrative, and FIG. 8 the operations represented in FIG. 8 can be performed in a number of different ways and can be split over different functional elements and in certain examples over different devices. It will also be appreciated that the sound processing module 851 can perform other operations, which have been omitted from for ease of illustration.

[0123] FIG. 7 Similar to the sound processing module 751 of FIG. 7 , the sound processing module 851 includes, among other elements, a fundamental frequency (F0) extractor 782, a pitch amplitude function 784, a channel energy detector 786, and a strategy determination module 788, each of which is implemented as described above with reference to

[0124] As noted above, the F0 extractor 782 is configured to extract the fundamental frequency (F0) of the received sound signal and output the fundamental frequency 783 and the pitch significance 785. The fundamental frequency 783 and the pitch significance 785 are provided to the pitch magnitude function 784, which outputs the pitch magnitude 787. As noted above, the channel energy detector 786 is configured to determine the energy in the lowest frequency channel regardless of whether the signal is harmonic / regular and output the pitch channel energy (PCE) 789.

[0125] The F0 application module 890 receives the pitch amplitude 787, the fundamental frequency 783, and the pitch channel energy 789. The F0 application module 890 includes a pulse energy block 794 and a pulse rate block 795. FIG. 8 In the example of FIG, the F0 application module 890 is configured to apply the fundamental frequency via a pulse rate. Specifically, the fundamental frequency determines the pulse frequency, and the pulse amplitude is determined by the pitch channel energy 789 and the pitch amplitude 787. Therefore, the F0 application module 890 determines and outputs pulse control parameters 891 (e.g., pulse amplitude and timing) to encode the fundamental frequency. The pulse control parameters 891 are provided to the arbitrator 892.

[0126] As noted above, strategy determination module 788 is configured to generate pulse control parameters 793 (e.g., pulse amplitude and amplitude timing) according to an initial predetermined / preset strategy and provide the parameters to arbitrator 892. Arbitrator 892 can operate similarly to arbitrator 792 to analyze pulse control parameters 891 and pulse control parameters 793 to generate stimulation control signals 837 representing electrical stimulation for delivery to a recipient via the top electrode assembly and / or the bottom electrode assembly of the cochlear implant.

[0127] It should be understood that FIG. 8 In the example of , the phase / timing cues can be restored to the F0 application process by additional signal analysis methods (e.g., zero crossing or peak picking). Such methods can preserve the interaural time difference cues.

[0128] FIG. 9 is a functional block diagram showing further details of an example embodiment of the F0 application module according to the embodiments presented herein. FIG. 9 In the example of , envelope modulation is used to impose / encode the fundamental frequency in the low frequency stimulation signal.

[0129] More specifically, in FIG. 9 FIG. 1 shows a functional block diagram of a sound processing module 951 of a top cochlear implant for optimizing speech / sound understanding using a top electrode assembly. It will be appreciated that FIG. 9 This logical arrangement is merely illustrative andFIG. 9 The operations described in connection with FIG. 9 can be performed in a variety of different ways and can be split over a variety of different functional elements and in some examples over different devices. It should also be appreciated that the sound processing module 951 can perform other operations, which have been omitted from FIG. 9 for ease of illustration.

[0130] Similar to the sound processing module 751, the sound processing module 951 includes, among other elements, a fundamental frequency (F0) extractor 782, a pitch amplitude function 784, a channel energy detector 786, and a strategy determination module 788, each of which is implemented as described above with reference to FIG. 7 FIG. 7. The sound processing module also includes an F0 imposition module 990 and an arbiter 992. FIG. 7

[0131] As noted above, the F0 extractor 782 is configured to extract the fundamental frequency (F0) of a received sound signal and output a fundamental frequency 783 and a pitch salience 785. The fundamental frequency 783 and the pitch salience 785 are provided to the pitch amplitude function 784, which outputs a pitch amplitude 787. As noted above, the channel energy detector 786 is configured to determine the energy in the lowest frequency channel regardless of whether the signal is harmonic / regular and outputs a pitch channel energy (PCE) 789.

[0132] The F0 imposition module 990 receives the pitch amplitude 787, the fundamental frequency 783, and the pitch channel energy 789. The F0 imposition module 990 includes a modulation depth block 996 that is configured to determine a modulation depth as a function of the pitch amplitude 787, where the greater the pitch amplitude, the greater the modulation depth. The F0 imposition module 990 also includes an envelope block 997 that determines a modulation rate based on the fundamental frequency 783. Additionally, the F0 imposition module 990 includes a carrier energy block that is configured to determine a carrier energy based on the pitch channel energy 789. A pulse amplitude is determined based on the modulation rate, the pitch channel energy 789, and the pitch amplitude 787. The pulse train rate can be, for example, 1200 pps, 1800 pps, etc. In this way, the F0 imposition module 990 imposes the fundamental frequency via envelope modulation of a high-rate pulse train.

[0133] Accordingly, the F0 imposition module 990 determines and outputs pulse control parameters 991 (e.g., pulse amplitude, modulation depth, rate, etc.) to encode the fundamental frequency. The pulse control parameters 991 are provided to the arbiter 992.

[0134] ​As noted above, the strategy determination module 788 is configured to generate pulse control parameters 793 (e.g., pulse amplitude and amplitude timing) in accordance with an initial predetermined / preset strategy and provide the parameters to the arbiter 992. The arbiter 992 can operate similarly to the arbiter 792 to analyze the pulse control parameters 991 and the pulse control parameters 793 to generate a stimulation control signal 937 representative of electrical stimulation for delivery to the recipient via the apical electrode assembly and / or the basal electrode assembly of the cochlear implant.

[0135] It will be appreciated that, in FIG. 9 the example, the phase / timing cues can be restored to the F0 application process by an additional signal analysis method (e.g., zero-crossing or peak picking). Such a method can preserve the interaural time difference cues.

[0136] FIG. 10 is a functional block of a sound processing module 1051 of the apical cochlear implant for optimizing speech / sound understanding by using the apical electrode assembly. The sound processing module 1051 is configured to perform a fundamental frequency (F0) application process to provide enhanced pitch cues within a stimulation signal delivered to the apical cochlear nucleus via the apical electrodes of the apical electrode array (i.e., adjust an initial stimulation strategy based on the fundamental frequency and channel energy to provide enhanced pitch cues at the apical stimulation channels). In this example, the fundamental frequency is applied / encoded via a peak selection (peak picking) process / technique.

[0137] It will be appreciated that, FIG. 10 the logical arrangement of FIG. 10 the operations represented in FIG. 10 may be performed in a number of different ways and can be split over different functional elements and, in certain examples, different devices. It will also be appreciated that the sound processing module 1051 can perform other operations that have been omitted from for ease of illustration.

[0138] In FIG. 10 the embodiment, the sound processing module 1051 includes, among other elements, a peak selector 1099, a channel energy detector 1086, a strategy determination module 1088, an F0 application module 1090, and an arbiter 1092. In FIG. 10 the example, the sound processing module 1051 receives a pre-processed channelized signal 1071 (e.g., similar to the pre-processed channelized signal 171 generated by the filter bank module 170 in FIG. 4 ). The pre-processed channelized signal 1071 is provided to the F0 extractor 1082, the channel energy detector 1086, and the strategy determination module 1088. While the pre-processed channelized signal 1071 is described with reference to the pre-processed channelized signal 171 inFIG. 10 It will also be appreciated, however, that the operations can be performed at least in part using other versions of the received sound signal (e.g., the electrical input signal received from the sound input, the pre-filtered output signal, etc.).

[0139] The peak detector 1099 is configured to use the lowest frequency channel or a wideband region to determine the pulse timing 1002 (e.g., pulse energy determined from energy in the same region as the peak picker or from energy in other regions). The limit on the update rate can be determined by a base frequency limit (F0_limit). The base frequency limit can be 500 Hz, but this value is merely exemplary. The pulse timing 1002 is provided to the F0 application module 1090.

[0140] As noted, the pre-processed channelized signal 1071 is provided to the channel energy detector 1086. The channel energy detector 1086 is configured to determine the energy in the lowest frequency channel regardless of whether the signal is harmonic / regular and outputs the pitch channel energy (PCE) 1089. In one example, the channel energy detector 1086 extracts energy in the wideband signal (e.g., the electrical input signal 167 received from the sound input device 133 or the pre-filtered output signal 169) to drive the apical stimulation channel(s) (i.e., the F0 application electrode(s)). In another example, the channel energy detector 1086 extracts energy only in the low frequency range / band (e.g., below 800 Hz). The low frequency range can be adjusted to match the frequency tonotopy and determine the appropriate frequency breakpoints on a per recipient basis, for example, by measuring the acoustic pitch in the contralateral ear related to the apical electrode and the next electrode.

[0141] The F0 application module 1090 receives the pulse timing 1002 and the pitch channel energy 1089. The F0 application module 1090 is configured to analyze these values and determine the pulse control parameters 1091 (e.g., pulse amplitude and timing) to encode the base frequency.

[0142] The strategy determination module 1088 is configured to generate the pulse control parameters 1093 (e.g., pulse amplitude and amplitude timing) according to an initial predetermined / preset strategy. That is, the strategy determination module 1088 uses the initial strategy to determine the pulse control parameters 1093 that are configured to apply sound information included in the received sound signal other than base frequency information. The initial strategy used to generate the pulse control parameters 1093 can be, for example, a CIS strategy, an ACE strategy, a 500 pps strategy, etc. In certain examples, a lower update rate strategy can be used that will supplement the F0 application electrodes.

[0143] Pulse control parameters 1091 encoding the fundamental frequency are provided to an arbiter 1092. In addition to these pulse control parameters 1091, the arbiter 1092 receives pulse control parameters 1093 from the strategy determination module 1088. The arbiter 1092 analyzes the pulse control parameters 1091 and the pulse control parameters 1093 to generate a stimulation control signal 1037 representing electrical stimulation for delivery to the recipient via the apical electrode assembly and / or the basal electrode assembly of the cochlear implant. In certain examples, the F0 application electrode(s) (e.g., one or more apical electrodes implanted in the apical region) will have a high weight in the arbitration decision. In certain embodiments, lower amplitude of pulse energy on the lowest frequency (pitch) channel can reduce the arbitration weight, but generally it will take more control relative to other channels. That is, the arbitration decision can be configured to be faithful to the low frequency timing, so when the arbitration process determines the stimulation control signal 1037, the arbitration process favors the low frequency channel.

[0144] In FIG. 8 and FIG. 10 examples, with an F0 application process involving rate pitch via fundamental extraction FIG. 8 ) or directly via peak picking FIG. 10 , the rate on the lowest frequency channel (one or more apical electrodes of the apical electrode assembly) will follow the associated fundamental frequency. Such an example pulse train is shown in FIG. 11 , where the pitch channel (EL1) represents 387 Hz at a rate of 387 pps (black at the bottom). The other channels are presented at a rate of 500 pps. The average rate per channel is 486 pps.

[0145] In FIG. 9 examples, with an F0 application process involving modulation, the lowest frequency channel will apply the pitch cues. Such an example pulse train is shown in FIG. 12 , where the sinusoidal amplitude modulation occurs at a high rate (500 Hz) and is reasonably represented by a 1500 pps carrier presented to the apical channel, which will not be on the other lower rate channels. In this example, the average rate per channel is 625 pps.

[0146] In one example of the embodiment of FIG. 9 , the result can be a CIS-like stimulation on the lowest frequency channel with a carrier frequency of 1500 pps, and another 8 maxima on the electrodes operating at 500 pps ACE. Alternatively, the result can be ACE-like stimulation on the lowest frequency channel, but can be stimulated more frequently.

[0147] Table 1 below shows potential example rates in accordance with certain embodiments presented herein. For eight (8) maximum presentation sets, even with one higher rate on one channel, the average rate will remain low. Note that the lowest frequency channel (EL1) at 1500 pps when mixed with 500 pps is still a low rate (equivalent to 8 maximum at 625 pps per channel).

[0148] Table 1:

[0149]

[0150] Generally, FIGS. 7-12 Embodiments of a full-spectrum coordinated stimulation strategy are generally shown, in which a fundamental frequency (F0) of a received sound signal can be encoded into a stimulation signal that is delivered via one or more of the direct low frequency channels (i.e., one or more of the apical electrode assemblies). It should be appreciated that the encoding of the fundamental frequency is one example, and other embodiments of the full-spectrum coordinated stimulation strategy can encode other or additional frequencies (e.g., second harmonics, third harmonics, etc.) into the stimulation signal that is delivered via one or more of the direct low frequency channels. The fundamental frequency can also be provided to more than one electrode.

[0151] FIG. 13 is a high-level flow diagram of a method 1300 in accordance with certain embodiments presented herein. The method 1300 begins at 1302, where one or more sound input devices of a cochlear implant receive a sound signal. The cochlear implant includes an apical electrode assembly including a plurality of apical electrodes and a basal electrode assembly including a second plurality of electrodes.

[0152] At 1304, the cochlear implant generates a plurality of stimulation signals representative of the sound signal. At 1306, the cochlear implant directly delivers a first subset of the plurality of stimulation signals to a first frequency topological region of the cochlea via one or more of the plurality of apical electrodes. The first frequency topological region is associated with acoustic frequencies below a predetermined threshold frequency. At 1308, the cochlear implant directly delivers a second subset of the plurality of stimulation signals to a second frequency topological region of the cochlea via one or more of the second plurality of electrodes of the basal electrode assembly.

[0153] Individuals suffer from different types of hearing loss (e.g., conductive and / or sensorineural) and / or different degrees / severities of hearing loss. However, many cochlear implant recipients now retain some residual natural hearing (residual hearing) after receiving a standard cochlear implant with only a base electrode assembly. For example, incremental improvements in the design of base stimulation components, surgical implantation techniques, tools, and the like have enabled atraumatic surgical procedures that preserve at least some of the recipient's delicate inner ear structures (e.g., cochlear hair cells) and natural cochlear function - particularly in the low frequency region of the cochlea.

[0154] Due at least in part to the ability to preserve residual hearing, not all recipients can initially be candidates for a tip cochlear implant by insertion of a tip electrode assembly, as recipients with residual hearing typically benefit from acoustic stimulation in addition to electrical stimulation. In these recipients, acoustic stimulation adds a more "natural" sound on top of the electrical stimulation signal.

[0155] However, over time, these recipients who initially retained some residual hearing can partially or completely lose this low frequency residual hearing. Accordingly, in accordance with certain embodiments presented herein, a tip cochlear implant can be an upgrade for recipients who previously had acoustic hearing in the low frequency region of the cochlea but have lost it. For example, when the low frequency hearing is lost, a tip electrode assembly can then be inserted and used as described elsewhere herein. In certain such examples, the tip electrode assembly can be added to a previously implanted cochlear implant (e.g., via some form of connector mechanism). In other examples, the tip electrode assembly can be placed in the recipient at the same time as a standard base electrode assembly (or a short base electrode assembly), but in a manner such that the tip electrode assembly is in an inactive state and positioned outside of the cochlea (e.g., placed along the skull). Other embodiments are also possible. Regardless, once it is determined that the recipient's low frequency hearing has been lost or dropped below an acceptable threshold level, the tip electrode assembly can be inserted into the apical region of the cochlea.

[0156] A tip cochlear implant in accordance with certain embodiments presented herein can also be an upgrade for recipients of only a standard base electrode assembly (or a short electrode assembly) who experience suboptimal device results. For example, if a recipient does not experience acceptable hearing performance with its base electrode assembly, a tip electrode assembly can be subsequently implanted to provide access to lower frequencies, eliminate frequency off-setting, and the like.

[0157] It should be appreciated that the above embodiments are not mutually exclusive and that various embodiments can be combined in various ways and arrangements.

[0158] The scope of the application described and claimed herein is not limited to the specific embodiments disclosed, as such embodiments are intended as illustrations of several aspects of the application. Any equivalents to the embodiments disclosed herein are intended to be within the scope of the application. Indeed, various modifications of the application, in addition to those shown and described herein, will become apparent to those skilled in the art from the foregoing description. Such modifications are intended to fall within the scope of the appended claims.

Claims

1. A method comprising: delivering a stimulation signal to an apical region of a cochlea of ​​a recipient of the implantable medical device via at least one electrode of a tip electrode assembly of the implantable medical device, wherein the tip electrode assembly is configured to be located at the apex of the cochlea; and At least a first portion of the stimulation signal is extracted via a bottom electrode assembly, wherein the bottom electrode assembly includes a plurality of electrodes and is configured to be implanted into the cochlea of ​​a recipient via a basal region of the cochlea.

2. The method of claim 1, wherein the tip electrode assembly comprises a plurality of electrodes.

3. The method according to claim 2, wherein the method comprises: delivering the stimulation signal via at least one electrode of the plurality of electrodes of the tip electrode assembly; as well as extracting at least a second portion of the stimulation signal via one or more of the plurality of electrodes of the tip electrode assembly, wherein the one or more electrodes are different from the at least one electrode.

4. The method according to claim 3, further comprising: The stimulation signal is delivered via the at least one electrode using a focused electrode configuration, wherein two or more of the plurality of electrodes of the tip electrode assembly draw the at least a second portion of the stimulation signal.

5. The method according to claim 1, further comprising: The first portion of the stimulation signal is drawn via two or more electrodes of the plurality of electrodes of the bottom electrode assembly.

6. The method according to claim 1, further comprising: At least a second portion of the stimulation signal is extracted via an extracochlear electrode implanted in the recipient outside of the recipient's cochlea.

7. The method of claim 1, wherein the top electrode assembly is physically separated and disconnected from the bottom electrode assembly.

8. The method according to claim 1, further comprising: receiving an acoustic signal at one or more acoustic input devices of the implantable medical device; as well as The stimulation signal is generated based on the sound signal.

9. The method according to claim 8, further comprising: generating an additional stimulation signal based on the sound signal; delivering the stimulation signal to evoke perception of a first frequency range of the sound signal; as well as The additional stimulation signal is delivered to the cochlea via at least one electrode of the plurality of electrodes of the bottom electrode assembly to evoke perception of a second frequency range of the sound signal.

10. The method according to claim 9, further comprising: At least a portion of the additional stimulation signal is drawn via the tip electrode assembly.

11. The method according to claim 9, further comprising: The sound signal is bandpass filtered via a bandpass filter to generate a set of bandwidth-limited channels, each of which includes a spectral component of the sound signal, wherein the bandpass filter has a non-uniform spectral width.

12. The method of claim 8, wherein generating the stimulation signal based on the sound signal comprises: The sound signal is processed to encode a fundamental frequency of the sound signal into the stimulation signal delivered via the at least one electrode of the tip electrode assembly.

13. The method of claim 12, wherein processing the sound signal so as to encode a fundamental frequency of the sound signal into the stimulation signal comprises: A pulse rate of the stimulation signal delivered via the at least one electrode of the tip electrode assembly is set to encode the fundamental frequency of the sound signal.

14. The method of claim 12, wherein processing the sound signal to encode a fundamental frequency of the sound signal into the stimulation signal comprises: Envelope modulation of the stimulation signal delivered via the at least one electrode of the tip electrode assembly is configured to encode the fundamental frequency of the sound signal.

15. The method of claim 12, wherein processing the received sound signal so as to encode a fundamental frequency of the sound signal into the stimulation signal comprises: A peak selection process is performed such that the stimulation signal delivered via the at least one electrode of the tip electrode assembly encodes the fundamental frequency of the sound signal.

16. The method of claim 1 , wherein delivering the stimulation signal to the apical region of the cochlea comprises: The stimulation signal is delivered to a frequency topographic region of the cochlea associated with acoustic frequencies below approximately 2 kHz.

17. The method of claim 1 , wherein delivering the stimulation signal to the apical region of the cochlea comprises: The stimulation signal is delivered to a frequency topographic region of the cochlea associated with acoustic frequencies below about 1 kHz.

18. The method of claim 1, further comprising: forming a cochlear incision in the inner ear of the recipient, proximal to the apical region of the cochlea; inserting the tip electrode assembly through the cochlear incision in the inner ear; as well as The bottom electrode assembly is inserted into the cochlea through an opening in the inner ear, wherein the opening in the inner ear is distinct from the cochlear incision.

19. A method comprising: providing a first current via a tip electrode of a plurality of tip electrodes of a tip electrode assembly, wherein the tip electrode assembly includes a first carrier member in which the plurality of tip electrodes are disposed; and A second current is provided via a bottom electrode of a plurality of bottom electrodes of a base electrode assembly including a second carrier member physically separate and disconnected from the first carrier member, the plurality of bottom electrodes being disposed in the second carrier member.

20. The method according to claim 19, comprising: The second current is drawn via at least one additional tip electrode of the plurality of tip electrodes of the tip electrode assembly.

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