Cochlear implants and methods for operating cochlear implants

Abstract

This invention provides a cochlear implant and a method for operating the cochlear implant to provide the user with more natural sound. [Solution] A cochlear implant comprising an electrode array including multiple stimulating electrodes for electrically stimulating helical ganglion cells corresponding to different frequencies, comprising: a voice processor that collects sound, analyzes the frequency (T) and sound pressure of the sound, and generates a control signal for the electrode array; a transmitter that transmits the control signal from the voice processor; and a receiver that receives the control signal transmitted from the transmitter and drives the stimulating electrodes according to the control signal. The control signal generated by the voice processor is a control signal that electrically stimulates helical ganglion cells corresponding to the received frequency (T) and simultaneously electrically stimulates helical ganglion cells corresponding to at least one integer fraction of the frequency (T / n).

Description

Technical Field

[0001] The present invention relates to a cochlear implant and a method for operating a cochlear implant.

Background Art

[0002] The cochlea of the inner ear is an important organ for perceiving sound. Inside the cochlea, there is a sensory epithelium strip that converts sound input as vibrations from the incus into electrical signals. The electrical signals generated in the sensory epithelium strip are transmitted to the auditory center via the spiral ganglion cells and are perceived as sound. The sensory epithelium strip has different reaction locations for each frequency of the input sound, and the difference in the reaction locations transmits the difference in the pitch of the sound.

[0003] Malfunctions of the sensory epithelium strip are one of the causes of hearing loss. However, when the spiral ganglion is functioning even if there is a malfunction in the sensory epithelium strip, it becomes possible to perceive sound by directly applying an electrical signal to the spiral ganglion cells. A device for applying an electrical stimulus corresponding to external sound to the spiral ganglion cells of a user to make the user perceive sound is a cochlear implant.

[0004] Current cochlear implants use an electrode array implanted in the cochlea to apply an electrical stimulus to the spiral ganglion cells. The cochlear implant includes an audio processor as a means for generating a control signal for the electrode array. The audio processor collects and computationally processes the sound around the user and generates a signal including frequency, intensity, generation timing, and the like.

[0005] Various voice processing technologies have been developed to address the usage environment and user needs of cochlear implants. For example, a continuous interleaved sampler method is known to prevent inappropriate current interactions. Furthermore, Patent Document 1 discloses a technique in which, within a signal frame with a predetermined sampling period, voice information is filtered and separated by frequency band, channel information for the corresponding frequency band is added to the voice information, the number of stimulation pulses is adjusted to a frequency permissible for one channel by retaining voice information with a high signal level for each channel, and then the number of stimulation pulses is adjusted to a frequency permissible for all channels overall by retaining voice information with a high signal level, and finally the voice information is sent to electrodes corresponding to the channels to generate stimulation pulses. However, there have been very few attempts to perform voice processing by focusing on the structure of the cochlea itself. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] International Publication No. 2005 / 013870 [Overview of the project] [Problems that the invention aims to solve]

[0007] Sounds that can be perceived through cochlear implants are still said to be unnatural compared to sounds that enter the ear from the normal external environment. In particular, distinguishing between high and low notes, such as musical scales, is said to be difficult.

[0008] This invention has been made in view of the current situation, and aims to solve the problem of providing a cochlear implant and a method for operating the cochlear implant in order to provide users with more natural sound. [Means for solving the problem]

[0009] The present invention relates to a cochlear implant. The cochlear implant of the present invention is a cochlear implant comprising an electrode array including a plurality of stimulating electrodes that electrically stimulate helical ganglion cells corresponding to different frequencies. The cochlear implant of the present invention comprises a voice processor that collects sound, analyzes the frequency (T) and sound pressure of the sound, and generates a control signal for the electrode array; a transmitter that transmits the control signal from the voice processor; and a receiver that receives the control signal transmitted from the transmitter and drives the stimulating electrodes according to the control signal. In the cochlear implant of the present invention, the control signal generated by the voice processor is characterized in that it electrically stimulates helical ganglion cells corresponding to the received frequency (T) and simultaneously electrically stimulates helical ganglion cells corresponding to at least one integer fraction of the frequency (T / n).

[0010] In the cochlear implant receiver of the present invention, it is preferable to generate current pulses on a stimulating electrode corresponding to the frequency (T), a stimulating electrode corresponding to half the frequency (T / 2), and a stimulating electrode corresponding to one-third the frequency (T / 3).

[0011] The electrical stimulation intensity of the stimulation electrode of the cochlear implant of the present invention is such that the intensity corresponding to half the frequency (T / 2) and one-third of the frequency (T / 3) is at least 20 dB lower than the intensity corresponding to the frequency (T). preferable.

[0012] The present invention also provides a method for operating a cochlear implant comprising an electrode array including a plurality of stimulating electrodes that electrically stimulate helical ganglion cells corresponding to different frequencies. The method for operating a cochlear implant of the present invention comprises the steps of: a voice processor collecting sound, analyzing the frequency (T) and sound pressure of the sound, and generating a control signal for the electrode array; a transmitter transmitting the control signal including frequency information; and a receiver receiving the control signal and driving the stimulating electrodes according to the control signal. In the method for operating a cochlear implant of the present invention, the control signal generated by the voice processor is characterized in that it electrically stimulates helical ganglion cells corresponding to the received frequency (T) and simultaneously electrically stimulates helical ganglion cells corresponding to at least one integer fraction of the frequency (T / n). [Effects of the Invention]

[0013] The cochlear implant and method of operating the cochlear implant of the present invention generate electrical stimulation based on the actual sound reception mechanism of the cochlea. Therefore, by electrically stimulating not only the spiral ganglion cells corresponding to the received frequency (T) but also the spiral ganglion cells corresponding to at least one integer fraction of the frequency (T / n), the accuracy of sound reproduction is higher than that of conventional cochlear implants, allowing the user to perceive more natural sounds and musical scales.

[0014] The cochlear implant and the method of operating the cochlear implant of the present invention have simple signal processing, which reduces the load on the voice processor and suppresses power consumption. [Brief explanation of the drawing]

[0015] [Figure 1] Figure 1 shows a human being wearing a cochlear implant. [Figure 2] Figure 2 shows the components that are placed inside the womb when using a cochlear implant. [Figure 3] Figure 3 shows a human being wearing a cochlear implant. [Figure 4] Figure 4 is a schematic diagram showing the structure of the cochlea in the inner ear. [Figure 5]Figure 5 shows the results of measuring the vibration of the sensory epithelial band of the hook part. [Figure 6] Figure 6 shows the results of measuring the vibration of the sensory epithelial band of the hook part. [Figure 7] Figure 7 shows the results of measuring the vibration of the sensory epithelial band of the hook part. [Figure 8] Figure 8 shows the results of measuring the vibration of the sensory epithelial band. [Figure 9] Figure 9 shows the results of measuring the vibration of the sensory epithelial band. [Figure 10] Figure 10 shows the results of measuring the vibration of the sensory epithelial band. [Figure 11] Figure 11 shows the results of measuring the vibration of the sensory epithelial band. [Figure 12] Figure 12 is a diagram schematically showing an example of the sound reception mechanism of the basilar plate of the cochlea. [Figure 13] Figure 13 is a diagram showing an example of the location where the current pulse of the stimulating electrode in the artificial inner ear of the present invention is generated. [Figure 14] Figure 14 is a diagram showing the location where the current pulse of the stimulating electrode in a conventional artificial inner ear is generated.

Mode for Carrying Out the Invention

[0016] The inventors measured the vibration of a part called the hook part in the cochlea of the inner ear in an animal (guinea pig) experiment, and found that in addition to the frequency (hereinafter also referred to as the optimal frequency) at which the sensory epithelial band of the cochlea shows the largest amplitude for the same intensity of input, the sensory epithelial band also vibrates at harmonics that are integer multiples of this optimal frequency, and thus arrived at the present invention. Hereinafter, the results of the vibration measurement of the cochlea with respect to sound will be described, and then the artificial inner ear of the present application and the operation method of the artificial inner ear will be described.

[0017] Sound entering the ear is transmitted as vibrations from the eardrum through the ossicles to the cochlea in the inner ear. The structure of the cochlea 20 is schematically shown in Figure 4. The cochlea 20 is a spiral-shaped organ, and inside the cochlea are the outer hair cells, the basilar plate, and the sensory epithelium 21 which contains the inner hair cells. Each of the spiral rings is called the basal turn 23, the middle turn 24, and the apical turn 25. The tip of the basal turn 23, which is the entrance to the cochlea 20, is called the hook 22.

[0018] When sound vibrations enter the cochlea 20, specific locations on the basal lamina of the sensory epithelial zone 21 vibrate, and the sensory hairs of the outer and inner hair cells also vibrate. The vibration of the sensory hairs of the inner hair cells generates electrical signals, so sound is converted into electrical signals here. The electrical signals generated by the inner hair cells are transmitted to the auditory center via spiral ganglion cells and afferent nerves, where they are perceived as sound. The sensory epithelial zone 21 vibrates in response to higher frequencies as you move from the apical rotation 25 to the basal rotation 23.

[0019] Figures 5 to 7 show the measurement results of the vibration of the hook portion 22 in response to sound input. Figure 5 shows the relationship between the distance (μm) from the entrance of the cochlea 20 and the amplitude (nm) for each frequency of the input sound. The input sound frequency was changed in 5kHz increments from 35kHz to 130kHz, and measurements were taken at three levels of loudness: 35dB, 45dB, and 55dB. The measurement results showed that the frequency at which the amplitude was largest for the same intensity input at the hook portion was 45kHz.

[0020] Here, vibrations were confirmed at the same hook location for the second and third harmonics at 45kHz and the surrounding 10kHz. The measurement results are shown in Figure 6. The measurement results confirmed that the same location that vibrated at 45kHz vibrated in response to the input sound. Figure 7 shows the relationship between the frequency (Hz) and amplitude (nm) of the input sound at the hook.

[0021] The hook section was found to vibrate significantly not only at a frequency of 45 kHz, but also at twice that frequency, 90 kHz, and three times that frequency, 135 kHz. However, the amplitude for the harmonics was only about 1 / 10 of the amplitude at 45 kHz, indicating a small response.

[0022] The results of this measurement suggest that when a sound vibration of a single frequency is input to the cochlea, in addition to the vibration of the sensory epithelium at a specific location that responds to the input frequency, the sensory epithelium at a location that vibrates in response to half the input frequency and the sensory epithelium at a location that vibrates in response to one-third of the input frequency also vibrates.

[0023] Furthermore, the relationship between the measurement location and vibration was measured when a specific frequency of sound was applied to the sensory epithelial zone of guinea pigs at location 26 (see Figure 4). The results are shown in Figures 8 to 11. The distance on the horizontal axis is the distance from a specific location at the bottom of the sensory epithelial zone (distance 0) to the measurement location at the top, expressed in units of μm.

[0024] The measured frequencies of 23kHz–26kHz and 46kHz–50kHz are both considered to be within the audible range for guinea pigs. The measurement results confirmed that the same area of ​​the sensory epithelium that vibrated at 23kHz–26kHz also vibrated at 46kHz–50kHz.

[0025] The measurement results confirmed that the sensory epithelium vibrates not only at frequencies previously considered to be perceptible as sound (24-25 kHz), but also at integer multiples of that frequency (48-50 kHz). Furthermore, similar to the vibration measurement results of the guinea pig hook portion 22 (results for vibrations at the fundamental frequency of 45-50 kHz and its second and third harmonics), it was confirmed that when a sound of a single frequency is input, the base plate at multiple locations vibrates.

[0026] When vibrations of sound within the audible range are input to the cochlea, it is thought that in addition to the vibration of the sensory epithelium at specific locations that respond to the input frequency, the sensory epithelium at locations that vibrate in response to half the input frequency and the sensory epithelium at locations that vibrate in response to one-third of the input frequency also vibrate.

[0027] Figure 12 schematically illustrates an example of the sound reception mechanism of the basilar plate of the cochlea 20, as confirmed by the above measurements. Figure 12 schematically shows the state in which vibrations of the cochlea and electrical signals are transmitted when an 18 kHz sound is input. For ease of understanding, the cochlea is shown unfolded and in a linear fashion in this figure. That is, in Figure 12, the left side is the basal rotation 23 side, and the right side is the vertex rotation 25 side.

[0028] When an 18kHz vibration is transmitted through the stapes, specific points on the basilar plate react and vibrate strongly, generating an electrical signal. Additionally, points that normally vibrate strongly in response to 9kHz and 6kHz vibrations also vibrate simultaneously, generating electrical signals. The amplitude of the vibration is typically largest at the points that vibrate in response to the 18kHz vibration, and therefore generates a strong electrical signal. The amplitudes at the points that respond to 9kHz and 6kHz vibrations are smaller, and the corresponding electrical signals are also smaller. These electrical signals are transmitted via afferent nerves to the auditory center and are perceived as sound.

[0029] Based on our understanding of the cochlea's response to sound, this embodiment of the cochlear implant is characterized by simultaneously transmitting electrical signals not only to spiral ganglion cells that transmit electrical signals corresponding to the frequency (T) of the input sound, but also to spiral ganglion cells that transmit electrical signals corresponding to an integer fraction of the input sound frequency (T) (T / n, where n is a natural number greater than or equal to 2). In particular, by generating current pulses on stimulating electrodes corresponding to frequency (T), half the frequency (T / 2), and one-third the frequency (T / 3), it is possible to generate electrical signals that are closer to how humans perceive sound with their ears and transmit them to the auditory center, thereby enabling the perception of highly reproducible sound. The following describes the form of the cochlear implant embodying this invention.

[0030] Figures 1 to 3 show an overview of the cochlear implant of this embodiment. The cochlear implant 1 comprises a voice processor 11, a transmitter 12, a receiver 13, an electrode array 14, and a standard electrode 15. The receiver 13 is implanted in the temporal region of the user. The electrode array 14 is an array of electrodes in which approximately 22 stimulating electrodes 14a are arranged in a row, and is implanted in the cochlea 20.

[0031] The operation of the cochlear implant of the present invention will now be described. The voice processor 11 collects sound generated around the user using its built-in microphone, analyzes the frequency, sound pressure, generation timing, etc., and generates a control signal to control the stimulating electrode 14a of the electrode array 14. The generated control signal includes the position of the stimulating electrode 14a that generates the current pulse, as well as the intensity and generation timing of the current pulse.

[0032] The audio processor 11 of this embodiment generates a control signal to simultaneously generate pulsed currents not only to the stimulating electrode 14a that electrically stimulates the spiral ganglion cells corresponding to the frequency (T) received by the microphone, but also to the stimulating electrode 14a that electrically stimulates the spiral ganglion cells corresponding to half the frequency (T / 2) and the stimulating electrode 14a that electrically stimulates the spiral ganglion cells corresponding to one-third of the frequency (T / 3).

[0033] The control signal generated by the voice processor 11 is sent to the transmitter 12, which in turn is sent to the receiver 13 inside the user's body. The receiver 13, in accordance with the received control signal, sends a signal to the target stimulating electrode 14a at the intensity and timing specified in the control signal to generate a pulsed current, thereby electrically stimulating the spiral ganglion cells that transmit electrical signals corresponding to the information of the stimulating electrode 14a frequency.

[0034] Figure 13 shows examples of the locations where the cochlear implant 1 of this embodiment generates current pulses on the stimulating electrode 14a when 18kHz, 9kHz, and 6kHz sounds are input.

[0035] In response to an 18kHz input sound, the audio processor 11 generates control signals to simultaneously stimulate spiral ganglion cells that respond to 18kHz, 9kHz, and 6kHz. At this time, the current value of the pulse current generated by the stimulating electrode 14a that stimulates the spiral ganglion cells that respond to 18kHz, the same frequency as the input sound, is adjusted to be at least 20dB louder in terms of volume compared to the current values ​​of the pulse currents generated by the stimulating electrodes that stimulate the spiral ganglion cells that respond to 9kHz and the spiral ganglion cells that respond to 6kHz.

[0036] For a 9kHz input sound, the audio processor 11 generates a control signal to simultaneously stimulate spiral ganglion cells that respond to 9kHz, 4.5kHz, and 3kHz. For a 6kHz input sound, the audio processor 11 generates a control signal to simultaneously stimulate spiral ganglion cells that respond to 6kHz, 3kHz, and 2kHz.

[0037] If the location of the spiral ganglion cells to be electrically stimulated is misaligned with the location of the stimulating electrode 14a, it is preferable to apply the necessary electrical stimulation by generating pulsed currents on both stimulating electrodes 14a. Alternatively, it is possible to apply the stimulation by generating pulsed currents only on the stimulating electrode closest to the spiral ganglion cells to be electrically stimulated. In either case, by electrically stimulating not only the spiral ganglion cells that respond to the same frequency as the input sound, but also the spiral ganglion cells corresponding to half and one-third of the input frequency, it is possible to perceive a more natural sound that is closer to the input sound.

[0038] As a comparative example, Figure 14 shows the generation points of current pulses generated at specific frequencies by the simplest cochlear implant's audio processor. The comparative audio processor generates a control signal that stimulates spiral ganglion cells that respond to 18kHz in response to an 18kHz input sound. When a 9kHz sound is input, it generates a control signal that stimulates spiral ganglion cells that respond to 9kHz. When a 6kHz sound is input, it generates a control signal that stimulates spiral ganglion cells that respond to 6kHz. While such signal processing has the advantage of being fast and having little interference, it has the disadvantage of making it difficult to reproduce complex sound information such as musical scales.

[0039] In contrast, the cochlear implant and the method of operating the cochlear implant of the present invention operate the electrode array in a manner that mimics the natural sound-receiving mechanism of the cochlea of ​​the inner ear, thus enabling the perception of sounds that are closer to natural sounds. [Explanation of Symbols]

[0040] 1 cochlear implant 11. Voice Processor 12 Transmitter 13 Receiving Unit 14 electrode arrays 14a stimulation electrode 20 Cochlea 21 Sensory epithelium 22 Hook section

Claims

1. A cochlear implant comprising an electrode array containing multiple stimulating electrodes that electrically stimulate spiral ganglion cells corresponding to different frequencies, A sound processor that collects sound, analyzes the sound frequency (T) and sound pressure, and generates control signals for the electrode array, A transmitter that transmits the control signal of the voice processor, A receiver that receives the control signal transmitted from the transmitter and drives the stimulating electrode according to the control signal, It is equipped with, The cochlear implant is characterized in that the control signal generated by the voice processor is a control signal that electrically stimulates helical ganglion cells corresponding to the received frequency (T) and simultaneously electrically stimulates helical ganglion cells corresponding to at least one integer fraction of the frequency (T / n).

2. The receiver, A stimulating electrode corresponding to the received frequency (T), A stimulating electrode corresponding to half the frequency (T / 2) of the aforementioned frequency, A stimulating electrode corresponding to a frequency that is one-third of the aforementioned frequency (T / 3) is used. The cochlear implant according to claim 1, characterized by generating an electric current pulse.

3. The intensity of the electrical stimulation from the aforementioned stimulating electrode is The cochlear implant according to claim 2, characterized in that the intensity corresponding to half the frequency (T / 2) and one-third of the frequency (T / 3) is 20 dB or less less than the intensity corresponding to the frequency (T).

4. A method for operating a cochlear implant comprising an electrode array containing multiple stimulating electrodes that electrically stimulate spiral ganglion cells corresponding to different frequencies, The process involves an audio processor collecting audio, analyzing the audio frequency (T) and sound pressure, and generating a control signal for the electrode array. The process involves the transmitter transmitting the control signal, which includes the frequency information, The receiver receives the control signal and drives the stimulating electrode according to the control signal, It is equipped with, A method for operating a cochlear implant, characterized in that the control signal generated by the sound processor is a control signal that electrically stimulates a spiral ganglion cell corresponding to a received frequency (T) and simultaneously electrically stimulates a spiral ganglion cell corresponding to at least one integer fraction of the frequency (T / n).

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