Automatic and individually optimised fitting of cochlear implants

Lead Research Organisation: University of Manchester
Department Name: Medical and Human Sciences

Abstract

A cochlear implant is a device to help deaf people hear. It translates sounds into electrical impulses applied to the hearing nerve in the ear. It is an important device that allows spoken communication and, for infants, the opportunity to develop spoken language. This project has two broad aims. The first is to develop ways to fit a cochlear implant without having to do lengthy tests involving the patients listening and making judgments about sounds. We will do this by directly measuring the activity of the hearing nerve and the brain in response to sounds. The second broad aim is to understand why different people are more or less successful with the implant, and, armed with this information, how to individually optimise the fitting so that the potential of each person is fully realised. Once again we will measure the responses of the hearing nerve and the brain to sounds, and use these to understand the differences in the way that each person hears with a cochlear implant. We can then find the significance of these differences for speech understanding and work out ways to optimise the settings of the sound processor based on individual characteristics. In summary, it is hoped that the research project will improve speech understanding with a cochlear implant, especially for those who currently do not do as well as their peers. Importantly, it is hoped that good quality fittings can be achieved for infants thus maximising their potential for spoken language development.

Technical Summary

This project has two broad aims: to improve methods of automatic fitting of cochlear implants using objective measures; and to use objective measures to assess individual differences in neural function that may be relevant to selection of optimal sound processing strategies.
We will use a combination of techniques which include psychophysical tests, mathematical modelling of hearing, speech perception tests, and electrophysiological measures of auditory pathways. Hypotheses are tested in cohorts of 20 adult cochlear implantees, and, where appropriate, methods will be further evaluated in a cohort of infants who use a cochlear implant. The objective measures used will be electrically-evoked compound action potential (ECAP), assessing function of the peripheral auditory nerve, long-latency auditory evoked potential (LAEP), including the acoustic change response (ACR) that reflects cortical response to a change in stimulus, and the electrically-evoked stapedial reflex (SR), a middle-ear muscle reflex to loud sounds that involves the brain stem auditory pathways.
The first three experiments aim to develop improved objective measures to determine the range of electrical currents used on each electrode without the use of behavioural data. The first two experiments explore ways of using ECAP and LAEP potentials respectively to determine the electrical current threshold levels on each electrode needed for fitting. In both cases the mathematical loudness model for electrical stimulation of McKay et al. is used in the development of the hypotheses and in the data analysis. The third experiment explores the relationship between the SR threshold and loudness using the same loudness model, and assesses the use of SR to determine the upper limit of electrical current used on each electrode for fitting the implant.
The last two experiments investigate the individual differences in peripheral and central neural response behaviour respectively, and seek relationships between these differences and perceptual ability. In the fourth experiment we test a specific hypothesis that the rate of stimulation which optimises speech understanding is related to the degree of peripheral neural survival or the functional refractory characteristics of the surviving neurons. In the final experiment we explore electrophysiological analogues of perceptual temporal and spectral resolution and determine their importance for speech understanding.
The overall outcome is hoped to be an improved and individually-optimised method of fitting patients using only objective rather than behavioural data. Improved fitting (and earlier fitting in infants) will lead to better outcomes, and hence quality of life, for people with a severe or profound hearing loss.

Publications

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Azadpour M (2014) Estimating confidence intervals for information transfer analysis of confusion matrices. in The Journal of the Acoustical Society of America

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Azadpour M (2013) Place specificity measured in forward and interleaved masking in cochlear implants. in The Journal of the Acoustical Society of America

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Azadpour M (2012) A psychophysical method for measuring spatial resolution in cochlear implants. in Journal of the Association for Research in Otolaryngology : JARO

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McKay CM (2010) Amplitude modulation and loudness in cochlear implantees. in Journal of the Association for Research in Otolaryngology : JARO

 
Description CPD for Australian audiologists
Geographic Reach Oceania 
Policy Influence Type Influenced training of practitioners or researchers
Impact Training for audiologists about the new options for patients suitable for auditory brainstem implants
 
Description workshop for audiological physicians at GOSH
Geographic Reach National 
Policy Influence Type Influenced training of practitioners or researchers
Impact Advice and knowledge of electrophysiological tests for diagnosis and prognosis of infants with auditory neuropathy spectrum disorder who are candidates for cochlear implantation
 
Description Cochlear Europe Ltd. PhD studentship funding
Amount £74,000 (GBP)
Organisation Cochlear Ltd. 
Sector Private
Country Global
Start 09/2010 
End 09/2013
 
Description Flexi Grant
Amount £4,963 (GBP)
Organisation Action on Hearing Loss 
Sector Charity/Non Profit
Country United Kingdom
Start 11/2010 
End 12/2010
 
Description Joint International Projects funding
Amount £10,000 (GBP)
Organisation The Royal Society 
Sector Charity/Non Profit
Country United Kingdom
Start 02/2009 
End 02/2011
 
Description Research Grant/The Help Ear and Allied Research Trust
Amount £17,500 (GBP)
Organisation Manchester University NHS Foundation Trust 
Department The Help Ear and Allied Research Trust (HEAR)
Sector Charity/Non Profit
Country United Kingdom
Start 08/2009 
End 12/2009
 
Description project grant
Amount £106,240 (GBP)
Organisation Advanced Bionics Inc. (AB) 
Sector Private
Country Global
Start 03/2011 
End 04/2012
 
Description project grant
Amount £17,000 (GBP)
Organisation Action on Hearing Loss 
Sector Charity/Non Profit
Country United Kingdom
Start 05/2010 
End 10/2010
 
Description project grant
Amount £20,000 (GBP)
Organisation Cochlear Ltd. 
Sector Private
Country Global
Start 08/2011 
End 09/2012
 
Description veski Innovation Fellowship
Amount $200,000 (AUD)
Organisation State Government of Victoria 
Sector Public
Country Australia
Start 07/2013 
End 09/2016
 
Title New artifact rejection method for electrically-evoked auditory potentials 
Description A new method of rejecting electrical artifact has been developed for us with cochlear implant electrophysiology that uses adaptations of independent component analysis 
Type Of Material Data analysis technique 
Year Produced 2012 
Provided To Others? Yes  
Impact The main impact will be the ability to assess auditory evoked responses for cochlear implants, leading to objective fitting methods and optimised fitting strategies. These will in turn lead to better outcomes and quality of life for hearing impaired people. Further funding has been obtained to apply a similar technique cortical responses for automatic fitting of cochlear implants (veski). 
URL http://doi:10.1016/j.heares.2013.04.005
 
Title New method for assessing place specificity of cochlear implant stimulation 
Description Previous attemptes to develop methods of assessing spatial selectivity of cochlear implant stimulation have all had flaws and have shown to be not useful for investigating reasons for variability in outcome. Our new method, based on psychohysical data, overcomes the problems in previous methods and so gives a valid measure of this factor. 
Type Of Material Physiological assessment or outcome measure 
Year Produced 2009 
Provided To Others? Yes  
Impact too early to have impacts realised, but the potential impact is on a clearer assessment of reasons for variability in outcomes with a cochlear implant, leading to optimised fitting strategies for individuals and better outcomes. 
 
Title New method for determining temporal resolution in cochlear implants 
Description We have showed that the method used in previous research to investigate temporal resolution was seriously flawed and have presented data with our new method that demonstrates significant differences from old data 
Type Of Material Physiological assessment or outcome measure 
Year Produced 2009 
Provided To Others? Yes  
Impact The new mthod is being used by other research groups 
 
Title New method for assessing place specificity of cochlear implant stimulation 
Description Previous attemptes to develop methods of assessing spatial selectivity of cochlear implant stimulation have all had flaws and have shown to be not useful for investigating reasons for variability in outcome. Our new method, based on psychohysical data, overcomes the problems in previous methods and so gives a valid measure of this factor. 
IP Reference  
Protection Protection not required
Year Protection Granted
Licensed No
Impact too early to have impacts realised, but the potential impact is on a clearer assessmment of reasons for variability in outcomes with a cochlear implant, leading to optimised fitting strategies for individuals and better outcomes.
 
Title New method for measuring auditory neural responses in cochlear implants 
Description The new method uses an ICA technique to extract resposne from artefact and avoids the issues with existing methods used in cochlear implant systems that may make the results inaccurate 
IP Reference  
Protection Protection not required
Year Protection Granted 2011
Licensed No
Impact We had confidential talks with an implant company who, in the end, did not consider it financially effective for it to be patented. However, the same company is very interested in the application of a similar technique to use for cortical responses and are interested in co-funding a study to develop this.
 
Description Clinical conference 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Type Of Presentation Paper Presentation
Geographic Reach National
Primary Audience Health professionals
Results and Impact The British Society of Ausiology (BSA) and British Academy of Audiology (BAA) conferences have largely audiology clinical professionals attending (between 100 and 300 delegates)

Clinicians provided feedback as to how my research was relevant to fitting of cochlear implants and counselling of patients
Year(s) Of Engagement Activity 2008,2009,2010,2011
 
Description Continuing Professional Development 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Type Of Presentation Keynote/Invited Speaker
Geographic Reach International
Primary Audience Health professionals
Results and Impact 100 Audiologists in Queensland, Australia heard about how historical and recent research innovations have contributed to the quality of life and communication ability of deaf individuals.

A relationship was formed with the Audiology Society of Australia, in which I am a key contact person for information flow between British and Australian Audiology societies re education and professional development
Year(s) Of Engagement Activity 2012,2013
 
Description consultancy with Phonak 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? No
Primary Audience Public/other audiences
Results and Impact I spent a day with research heads of the hearing aid company Phonak explaining what the issues were with cochlear implant design and fitting, as they were interested in beginning to manufacture cochlear implants

The company has decided to contribute significantly to the implant field and have now bought the major US implant company, Advanced Bionics
Year(s) Of Engagement Activity 2009
 
Description invited international lectures 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Type Of Presentation Keynote/Invited Speaker
Geographic Reach International
Primary Audience Undergraduate students
Results and Impact Lecture tour to China to provide lectures to audiology students about cochlear implants

Possible future PhD students for Manchester and other UK universities.
Year(s) Of Engagement Activity 2011
 
Description public lecture 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Type Of Presentation Keynote/Invited Speaker
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact This was a public lecture in the centre of Melbourne. About 100 people attended, including members of the deaf community, any interested public, and professionals related to hearing health care. It raised interest and awareness in the current and future use of technology to help hearing imparied people. Many questions from the public about the future treatments for deafness.

Awareness from private endowment source of the importance fo our work
Year(s) Of Engagement Activity 2011
 
Description veski events 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? Yes
Type Of Presentation Keynote/Invited Speaker
Geographic Reach International
Primary Audience Media (as a channel to the public)
Results and Impact A combination of media, school teachers, scientists, and government ministers attended the event in which my veski fellowship was announced.

A newspaper article followed from the announcement event, which highlighted my new research programme to the public. Also, a science teacher has organised for me to visit her school to talk about my research and careers in science.
Year(s) Of Engagement Activity 2013
URL http://www.veski.gov.au