WO2018208265A2 - A novel method of frequency coding of an electrode to promote spatial selectivity and speech discrimination in cochlear implants - Google Patents

Abstract

The present invention relates to a novel method of frequency coding of an electrode to promote spatial selectivity and speech discrimination in cochlear implants, which ensures changing the basic working principle of devices that operate hearing and hearing aid prosthesis devices that operates with a 60-70% efficiency and cochlear implants in particular and a more efficient operation for said devices.

Description

A NOVEL METHOD OF FREQUENCY CODI NG OF AN ELECTRODE TO PROMOTE SPATI AL SELECTI VI TY AN D SPEECH DISCRIMINATI ON I N COCHLEAR IMPLANTS

TECH N I CAL Fl ELD OF THE I NVENTI ON

The present invention relates to a novel method of frequency coding of an electrode to promote spatial selectivity and speech discrimination in cochlear implants, which ensures changing the basic working principle of devices that operate hearing and hearing aid prosthesis devices with a 60-70% efficiency and cochlear implants in particular and a more efficient operation for said devices.

THE PRI OR ART

Severe sensorineural hearing loss is an extremely widespread condition in societies and it constitutes a significant public health problem (Brand et al., 2014). Routine newborn hearing screening operations are applied to all newborns for early detection of sensorineural hearing losses half of which are congenital and amplifying timely hearing (Ulusoy et al., 2014; Bolat et al., 2009). Some part of the sensorineural hearing losses occur at later ages. Many of these hearing losses are cochlear-type nero sensorineural hearing losses; in other words they are originated from the inner ear diseases. No matter what type of sensorineural hearing losses including congenital and acquired ones, current treatment applied to the bilateral cochlear-type sensorineural hearing losses is performed by means of cochlear implantation (Brand et al., 2014).

Approximately 500 cochlear implantation surgeries per year are performed in our country (Incesulu, 2014). There have been recorded high level of successes in treatment of advanced hearing losses by using cochlear implantation applications that have been implemented in our country since 1987 (Altay and Konrot, 2006). Furthermore, there are some deficiencies to be corrected in relation to cochlear implantations that are currently performed around the world. Prominent ones among these deficiencies are low spatial selectivity of cochlear implants and their related disadvantages in speech discrimination (Zhu et al., 2012; Cullington and Zeng, 2011). The patients with cochlear implants have a difficulty in hearing speech in a noisy environment, in hearing while other people are speaking mutually (in a competitive manner) and in musical hearing (pitch perception) (Wang et al., 2011; Gfeller et al. 2008). Moreover, they have certain challenges in communication in some tonal languages such as Chinese (Wang et al.,2011).

Severe sensorineural hearing loss is an extremely widespread condition in societies and constitutes a significant public health problem. Routine newborn hearing screening operations are applied to all newborns for early detection of sensorineural hearing losses half of which are congenital and amplifying timely hearing. Some part of the sensorineural hearing losses occur at later ages. Many of these hearing losses are cochlear-type nero sensorineural hearing losses; in other words they are originated from the inner ear diseases. No matter what type of sensorineural hearing losses including congenital and acquired ones, current treatment applied to the bilateral cochlear-type sensorineural hearing losses is performed by means of cochlear implantation. In the event of advanced or total hearing losses in other words, that cochlea is not able to process acoustic signals, cochlear implantations process the acoustic signals and transform them into electrical signals and then transmit the same to auditory nerve tissues. Cochlear implantations generally consist of three main parts. These parts are microphone, processor and electrode. The microphone transforms sound waves into electrical signals; the processor modulates the amplitude and frequency of these signals and finally transmits them to the electrodes in order to stimulate the auditory nerve. There have been recorded high level of successes in treatment of advanced hearing losses by using cochlear implantation applications. Furthermore, there are some deficiencies to be corrected in relation to cochlear implantations that are currently performed around the world. Prominent ones among these deficiencies are low spatial selectivity of cochlear implants and their related disadvantages in speech discrimination. The patients with cochlear implants have a difficulty in hearing speech in a noisy environment, in hearing while other people are speaking mutually (in a competitive manner) and in musical hearing (pitch perception). Moreover, they have certain challenges in communication in some tonal languages such as Chinese. There is a need for promoting frequency selectivity and sensitivity of implants in order to overcome the disadvantages in spatial selectivity and speech discrimination of the prior art cochlear implant technology. In the present cochlear implants, the changes that will be made depending on the previous works regarding the related programming for the frequency selectivity and frequency modulations of electrodes will also promote spatial selectivity, speech discrimination and hearing ability in noise. Electrode arrays in cochlear implants in the prior art hearing aid prosthesis devices were prominently arranged according to the travelling wave theory of von BEKESY (travelling wave) that was put forward on frequency selectivity of the cochlea. Recent studies have shown that the aforementioned theory has failed to clearly explain the frequency selectivity of cochlea and cochlea is a bionic mechanic- amplifier that receives and analyses and then transmits sound. Since the travelling wave theory was implemented cadaverously, the fact that cellular formations do not show biological characteristics and cochlea develops linear responses against the stimulant have resulted in incorrect assessments in sound analysis and some technical drawbacks in spatial selectivity, speech discrimination and hearing in noise regarding the frequency selectivity in the auditory system. In the present invention, frequency selectivity is disclosed in accordance with the travelling wave theory. Electrode arrays in cochlear implants are aligned from the high frequency sounds to the low frequency sounds. Design of the electrodes follows an order like high frequencies- medium frequencies- low frequencies.

The present invention relates to a novel method of frequency coding of an electrode to promote spatial selectivity and speech discrimination in cochlear implant, which also aims at overcoming the aforementioned drawbacks and the said invention has a different system relative to the latest prior art applications.

SUMMARY OF THE I NVENTI ON

The present invention relates to a novel method of frequency coding of an electrode to promote spatial selectivity and speech discrimination in cochlear implant with the aim of overcoming the aforementioned problems and ensuring new advantages for the related technical field.

An aim of the present invention is to provide a method which ensures changing the basic working principle of devices that operate hearing and hearing aid prosthesis devices that operate with a 60-70% efficiency and cochlear implants in particular and a more efficient operation for said devices.

The present invention relates to a novel method of frequency coding of an electrode to promote spatial selectivity and speech discrimination in cochlear implant so as to achieve all aims that are discussed above and will be apparent from the following detailed description.

BRI EF DESCRI PTI ON OF DRAW I NGS

FIGURE 1 shows the prior art view of the invention. FIGURE 2 shows electrode array of the cochlear implant.

Definitions of the Components / Portions/ Parts of the I nvention

Parts/portions/components in the figures presented for a better understanding of the invention with the title of the method of frequency coding of an electrode to promote spatial selectivity and speech discrimination in cochlear implant are individually numbered and the description of every related number is presented below.

1 Microphone

2 Processor

3 Electrode

3a A portion for receiving the high-medium-low frequency sound stimulations in the electrode

3b A portion for receiving the high-medium-low frequency sound stimulations in the electrode

3c A portion for receiving the high-medium-low frequency sound stimulations in the electrode

DETAI LED Dl SCRI PTI ON OF THE I NVENTI ON

In this detailed description of the innovation according to the present invention, a novel method of frequency coding of an electrode to promote spatial selectivity and speech discrimination in cochlear implant, without limitation, is disclosed with the help of some examples for a better understanding of the issue.

Referring to Figure 1, the prior art of the present invention is presented. In Figure 1, the prior art components including a microphone (1), a processor (2) and an electrode (3) are shown. Pattern of the frequency array of the electrode (3) is decreasing from the high frequencies to the low frequencies, for example the order is like the following; 8000 Hz-4000 Hz-2000 Hz-1000 Hz-500 Hz-250 Hz.

With reference to Figure 2, the electrode array of cochlear implant of the present invention is presented. In Figure 2, the components including the microphone (1), the processor (2) and the electrode (3) are shown. A portion for receiving the high-medium-low frequency sound stimulations in the electrode is represented with 3a (an exemplary order; 8000 Hz-4000 Hz-2000 Hz-1000 Hz-500 Hz-250 Hz), a portion for receiving the high- medium-low frequency sound stimulations in the electrode is represented as 3b (an exemplary order; 8000 Hz-4000 Hz-2000 Hz-1000 Hz-500 Hz-250 Hz) and a portion for receiving the high-medium-low frequency sound stimulations in the electrode is represented as 3c (an exemplary order; 8000 Hz-4000 Hz-2000 Hz-1000 Hz-500 Hz-250 Hz). Each patient to be subjected to an administration can be provided with individual arrays depending on the numbers of their current electrodes actively acting within the cochlea by individual.

There is need for promoting frequency selectivity and sensitivity of implants in order to overcome the drawbacks regarding spatial selectivity and speech discrimination of the present cochlea implant technology (Zhu et al., 2012). In this respect, laser cochlear implants and intraneural auditory implants which still have need of development are promising (Matic et al. 2013; Middlebrooks and Snyder, 2007). Furthermore, we envisage that some adaptations will contribute to spatial selectivity, speech discrimination and hearing in noise in a positive way depending on our previous studies (Bulut et al. 2012; Bulut et al. 2013) in the related programming of frequency selectivity and frequency modulations of the electrode without making a particular technological innovation for the current cochlear implants.

Our recent three empirical studies (Bulut et al. 2008a, 2008b, 2009a, 2009b) have shown that SOAE stimulating records in the presence of the contra lateral acoustic stimulator in the first stage are modified and outer hair cells show specific activity for frequency and these are recorded (Bulut et al.2008a). In an another study that we carried out, there were obtained some cues in relation to the use of efferent blocker considering that this activity is transferred from the opposing ear though the efferent innervations of the outer hair cells (Bulut et al.2009). The use of apamin as efferent blocker and temporary blockage of the SOAE activity that is formed by contra lateral stimulation following the blockage supported this hypothetical approach. Also we acquired an interesting study environment in our first study due to the fact that the acoustic stimulator of pure tone from right ear was applied so as to cause a hearing loss and pure tone hearing loss was an outcome. In said environment, these frequency-specific outer hair cells would be damaged in the right ear but SOAE would be undamaged in the left ear in which we performed the recording. In such an assembly, acoustic stimulators of pure tone that we transmitted through the right ear resulted in the frequency-specific activity again (Bulut et al. 2008a). In this case, the process of transferring the sound transmitted to the right ear to the left ear should be performed by the activity of inner hair cells in the right ear rather than the activity of outer hair cells. In other words, the sound that is transmitted to either one of the ears is firstly received by the inner hair cells and then transferred to both ipsilateral and contra lateral outer hair cells for frequency analysis. In our study, that we utilized acoustic stimulators of pure tone instead of the narrow band or noise-type acoustic stimulators that are typically used in such studies under normal conditions made possible to reveal that the related frequency information is transferred (Bulut et al. 2008a). In an ultra structural examination after acoustic trauma in our further study, it was shown that frequency-specific acoustic trauma which was generated by pure tone was formed as a segmenting means in different outer hair cell ranges throughout the cochlea (Bulut et al. 2008b) instead of being formed in a specific area (maximum vibration point) as being frequency-specific to which a stimulation was transmitted on basilar membrane in the cochlea in accordance with the travelling wave theory of von Bekesy. In consequence of aforementioned studies (Bulut, 2009b), it has been appreciated that the frequency identification would be directly performed on the outer hair cells and all frequency responses would be ensured for all segments in the cochlea depending on that frequency selectivity in cochlea led to primermotile responses in different outer hair cell groups on cochlea instead of tonotopic distribution in given auditory physiology and frequency distribution which occurs from high-pitched frequency to low- pitched frequency, which is also from basal to apex in cochlea.

Our present invention also provided that high frequency regions in the order on electrodes of the cochlea implant enclosed high-medium-low frequency regions and similarly the other frequency regions comprised high-medium-low frequency regions as well and frequency- specific local order was not observed in cochlea, the part of the cochlea which only enclosed high-frequencies provided responses for high-medium-low frequencies and this frequency order was repeated in all segments throughout the cochlea according to our empirical studies.

All cellular structures in cochlea show frequency-specific different mechanical characteristics and the most prominent and anatomically varying ones among these cellular structures are the outer hair cells. The length of cell is short in the high frequency region and the length of the same in the low frequency region is long. Outer hair cells throughout the cochlea are isolated from each other in other words they are not in contact with each other. If frequency selectivity in cochlea was performed on basilar membrane as stated in the travelling wave theory of von Beksy, outer hair cells would not have to show frequency- specific different anatomical characteristics. Outer hair cells can change the length of cell with a motor protein (Prestin) within the cell membrane. Changes in the length of cell can be performed by both stimulating characteristic of the cell itself and though a system (Olivocochlear System) that can establish neural connections with it. These unique characteristics of outer hair cells made possible for us to assess it as a cell at the center of frequency selectivity and build our studies on this aspect. We put forward a hypothesis regarding that frequency selectivity in cochlea can be performed though the outer hair cells by means of the olivocochlear system. Because the outer hair cells can provide audio frequency i.e. frequency responses with the changes in the length of cell and the olivocochlear system modulate can these responses. This modulation and electromotile responses of outer hair cells can provide response for all audio frequencies to which stimulation is transmitted in every segment of cochlea.

We established a hypothesis on that frequency selectivity in cochlea can be generated though the outer hair cells by means of olivocochlear system and tested said hypothesis by using electrophysiological and ultrastructural studies.

Within the framework of our hypothesis, we firstly assessed cochlea with both electrophysiological tests and in ultrastructural-cellular aspect by generating frequency- specific acoustic damage or audio trauma and pure tone acoustic trauma, which had been never applied in the literature. When we generated frequency-specific acoustic trauma in our electrophysiological measurements, we observed more damages in frequency band particularly to which we generated trauma while the other all frequency bands affected by the damage much less. Devices that we utilized in electrophysiological measurements executed recordings in accordance with the theory of Bekesy and assessments in compliance with the same. Therefore, it was not surprising to see that frequency bands to which acoustic trauma was generated were affected but we also observed that the other frequency bands were affected. This led us to ponder to assess acoustic trauma in cellular aspect. When we carried out an ultrastructural examination in cochlea by using Scanning Electrode microscope based on the damage in the other frequency bands, we observed and assessed the trauma regions that were not compatible with the electrophysiological records in frequency band, expanded through the entire cochlea and were completely distant from the localism principle in frequency selectivity of cochlea. If the theory of Bekesy was true, we would have observed that the outer hair cells had been affected by the frequency-specific acoustic trauma in this region (120 dBSPL at the maximum stimulator magnitude- for 20 minutes) but we actually observed that different regions throughout the entire cochlea were affected. We observed that outer hair cells had an important role in frequency selectivity of cochlea and the cochlea generated frequency responses in the light of the data that we obtained based on our studies. We evaluated that frequency responses that were generated were modulated with the olivocochlear system. Bekesy failed to observe the outer hair cell responses due to his theory that he performed cadaverously and revealed that frequency responses were generated by the basal membrane movement. Furthermore, we suggest that the basal membrane movement that was generated based on the frequency mentioned by Bekesy in his theory was formed by the frequency responses of outer hair cells. Since basal membrane has support cells thereon (they do not show frequency-specific morphological variations) and the support cells have the outer hair cells thereon. Basal membrane here was likely to supporting outer hair cells to be included within a better resonance frequency.

The advantageous and authenticity of our present invention is to change the basic working principle of devices that operate hearing and hearing aid prosthesis devices that operates with a 60-70% efficiency and cochlear implants in particular and to ensure a more efficient operation for said devices.

The present invention relates to a novel method of frequency coding of an electrode to promote spatial selectivity and speech discrimination in cochlear implant, characterized in that the method comprises the following components consisting of; » Outer hair cells to be used for modulation of frequency selectivity, generating frequency responses in cochlea,

• Olivocochlear system for modulating frequency responses in cochlea,

• Cochlear Implant that is required for hearing losses,

• Electrode Array that ensures promoting frequency resolution in auditory system and speech discrimination in different environments and auditory processing in tonal perceptions,

• Frequency selectivity for describing of how audio frequency is analyzed in cochlea,

• Basilar membrane for explaining frequency selectivity in cochlea via basilar membrane with travelling wave theory of Von Bekesy REFERENCES

Altay, B. and Konrot, A. 2006. "History of Cochlear Implant and Its Development in Our Country ", Turkey Clinics, J Surg Med Sci, 2(10), 1-6.

Brand, Y. et al. 2014. "Cochlear implantation in children and adults in Switzerland", Swiss Med Wkly, 4(144), wl3909.

Bolat, H. et al. "National newborn hearing screening program in Turkey: struggles and implementations between 2004 and 2008", Int J Pediatr Otorhinolaryngol, 73(12), 1621-1623.

Bulut E, Ozturk L, Uzun C. 2008. "Frequency Discrimination By Outer Hair Cells: I- Functional Status In Contralateral Pure-Tone Acoustic Trauma", VIII^th Internaitonal Conferences Cholesteatoma&Ear Surgery, Antalya, Mediterranean Journal of Otology, p. 63.

Bulut E, Uzun C, Ozturk L. 2008. "A New Approach to Frequency Selectivity of Cochlear: Active-Effective Coding. II- Electro physiologic and Ultra structural Evidences ", 8th International Congress of Otorhinoiaryngoiogy and Head and Neck Surgery, Ankara.

Bulut E, Ozturk L, Uzun C. 2009. "Spontaneous Otoacustic Emission Records in Medial Efferent System Activation: An Analysis of Cochlear Frequency Bands with Pure- Sound Contra lateral Acoustic Stimulation in Efferent Blocker-Encouraged Subjects", 31'st Turkish National Otorhinoiaryngoiogy and Head and Neck Surgery Congress Abstract Book, p.136, Antalya.

Bulut E. 2009. "Role of outer hair cells in Corti organ frequency selectivity", Ph.D. Thesis, Edirne.

Cullington, H. E. and Zeng, F. G. 2011. "Comparison of bimodal and bilateral cochlear implant users on speech recognition with competing talker, music perception, affective prosody discrimination and talker identification". Ear Hear, 32(1), 16-30. G feller, K. et al. 2008. "Multivariate Predictors of Music Perception and Appraisal by Adult Cochlear Implant Users". J Am Acad Audiol, 19(2), 120-134.

incesulu, A. 2014. (personal interview).

Matic, A. I. et al. 2013. "Behavioral and Electrophysiological Responses Evoked by Chronic Infrared Neural Stimulation of the Cochlea". PLoS ONE, 8(3), e58189.

Middle brooks, J. C. and Snyder, R.L 2007. "Auditory prosthesis with a penetrating nerve array". J Assoc Res Otolaryngol, 8(2), 258-279. Susan, B. et al. 2014. Cochlear Implants (Third Edition). Newyork: Thieme Medical Publisher, Inc.

Ulusoy, S. et al. 2014. "The results of national newborn hearing screening (NNHS) data of 11,575 newborns from west part of Turkey", Eur Rev Med Pharmacol Sci,18(20), 2995-3003.

Wang, W. et al. 2011. "Musical pitch and lexical tone perception with cochlear implants". International Journal of Audiology, 50, 270-278.

Zhu, Z. et al. 2012 "Cochlear-implant spatial selectivity with monopolar, bipolar and tripolar stimulation", Hear Res, 283(1-2), 45-58.

Claims

CLAI MS

The present invention relates to a novel method of frequency coding of an electrode to promote spatial selectivity and speech discrimination in cochlear implants, characterized in that the method comprises the following components consisting of;

• Outer hair cells to be used for modulation of frequency selectivity, generating frequency responses in cochlea,

• Olivocochlear system for modulating frequency responses in cochlea,

• Cochlear Implant that is required for hearing losses,

· Electrode Array that ensures promoting frequency resolution in auditory system and speech discrimination in different environments and auditory processing in tonal perceptions,

• Frequency selectivity for describing of how audio frequency is analyzed in cochlea,

• Basilar membrane for explaining frequency selectivity in cochlea via basilar membrane with travelling wave theory of Von Bekesy.