Graeme Clark (doctor)

Graeme Milbourne Clark AC (born 16 August 1935) is an Australian doctor. He was a key figure in the research and development of the Bionic Ear – a multiple-channel Cochlear Implant.

Early life

Clark was born in Camden, New South Wales on August 16, 1935. As a young boy, Clark’s father became deaf and this inspired his lifelong mission to help deaf people.

Education

Clark attended Camden Primary School and then Sydney Boys High for one year. The remainder of his secondary education was in Royle House at Scots College in Sydney. He then went on to study medicine at the University of Sydney, graduating in 1957 with a Bachelor of Medicine, Bachelor of Surgery (MBBS) with honours and was top of his year. He continued his studies in 1962, in general surgery at the Royal College of Surgeons in Edinburgh.

Early work

He then he specialised in ear nose and throat surgery at the Royal National Throat Nose and Ear Hospital and obtained a fellowship in 1964 from the Royal College of Surgeons, London. Clark then returned to Australia and became a Fellow of the Royal Australasian College of Surgeons and in 1969 completed his PhD at the University of Sydney on “Middle Ear & Neural Mechanisms in Hearing and in the Management of Deafness”. At the same time, he completed a Master of Surgery thesis on “The Principles of the Structural Support of the Nose and its Application to Nasal and Septal Surgery’.

In 1976 he returned to England to study at the University of Keele, and to learn more about speech science, as this knowledge was also essential for enabling him to work on converting complicated speech signals into electrical stimuli of the hearing nerve.

Development of cochlear implants

Motivated not only by his father’s deafness but inspired by the life works of Louis Pasteur, Clark considered the notion that hearing, particularly for speech, might be reproduced in people with deafness if the damaged or underdeveloped ear were bypassed and the auditory nerve electrically stimulated, to reproduce the coding of sound. His initial doctoral research at the University of Sydney investigated the effect of the rate of electrical simulation on single cells and groups of cells in the auditory brainstem response, the centre where frequency discrimination is first decoded. His study showed the limitation of reproducing speech frequencies using a temporal code. At the completion of his PhD in 1969 he considered that more work was required to decide which signals were of greatest importance in speech perception.

Clark’s research demonstrated that an electrode bundle with 'graded stiffness' would pass without injury around the tightening spiral of the cochlea to the speech frequency region. Until this time he had difficulty identifying a way to place the electrode bundle in the cochlea without causing any damage. A breakthrough was achieved during a vacation at the beach – using a seashell to replicate the human cochlea and grass blades (which were flexible at the tip and gradually increasing in stiffness) to represent electrodes.

Further modifications to his model were made. Clark showed that the electrode bundle had to be free-fitting and the wires terminated with circumferential bands to reduce friction against the outer wall of the cochlea, and so make it easier to pass the required distance. The bands had to be wide enough to minimize the charge density of the electrical current for safety, but narrow enough for localized stimulation of the nerve fibers for the place coding of frequency. In order to satisfy questions about the safety of the device Clark conducted experiments to show that there was a minimal risk of meningitis from a middle ear infection if a fibrous tissue sheath grew around the electrode bundle. The sheath was developed from a connective tissue graft from the person’s own body that was placed around the electrode bundle where it entered the cochlea. The ultimate question however was: could speech be coded with multi-channel stimulation so that it could be understood by a deaf person? and this could only be discovered by operating on a deaf person. When he first started making the Bionic Ear, no one believed that he could do it as the ear was so delicate to operate on.

The First Implant - 1978

The first multi-channel cochlear implant operation was done at the Royal Victorian Eye and Ear Hospital in 1978 by Clark and Dr Brian Pyman. The first person to receive the implant was Rod Saunders who had lost his hearing aged 46.

Breakthrough

After successfully completing the surgery Clark in 1978 discovered with his post-doctoral colleague Yit Chow Tong how multi-channel electrical stimulation of the brain could reproduce frequency and intensity as pitch and loudness in severely-to-profoundly deaf adults who originally had hearing before going deaf. Electrical stimulation at low rates of 50 pulses/s was perceived as a pitch of the same frequency, but at rates above 200 pulses/s what was heard was poorly discriminated and a much higher pitch. This discovery established that the timing of electrical stimuli was important for low pitch when this had been difficult to determine with sound. But discrimination of pitch up to 4000 Hertz is required for speech understanding, so Clark emphasized early in the development of the cochlear implant that place coding through multi-channel stimulation would have to be used for the important mid-to-high speech frequencies. Clark and Tong next discovered that place of stimulation, was experienced as timbre, but without a strong pitch sensation. The patient could identify separate sensations according to the site of stimulation in the cochlea. Furthermore, if the pitch-like sensations from rate and place of stimulation were combined one could influence the other. Thus a lower rate of stimulation on a higher pitched electrode with sharp timbre corresponded to a higher rate on a lower pitched electrode with dull timbre. He next made the very important discovery in 1978 that when individual electrodes were stimulated the sensations not only varied from sharp to dull, but were recognized as vowel-like. The vowels corresponded to those that had second formant frequencies that would excite the same region in a normal hearing person. Formants are concentrations of frequency energy due to vocal tract resonances, and they are important for intelligibility of speech. If pairs of electrodes were stimulated together at a constant stimulus rate the vowel perceived was different from that perceived with single electrode stimuli. When two electrodes were stimulated at different rates a consonant was perceived. The consonant was related to the difference in rate between the stimuli on the electrodes.

Clark and Tong at the end of 1978 then made the ground-breaking discovery - the first speech processing strategy to give open-set speech understanding to severely-to-profoundly deaf people using electrical stimulation alone, and in combination with lipreading. The speech processing strategy coded the second formant as place of stimulation along the cochlear array, the amplitude of the second formant as current level, and the voicing frequency as pulse rate across the formant channels.

Clark in December 1978 arranged that his audiologist present open-set words to his first patient, who was able to identify several correctly. Clark realized then that this was the breakthrough in providing speech understanding that everyone had been hoping for. To quote from Clark’s autobiography (Sounds from Silence Allen & Unwin, 2000) “it was the moment I had been waiting for. I went into the adjoining room and cried for joy.”

This discovery was established by Clark with objective audiological tests in 1979. The open-set speech test results on this patient were the first time that speech recognition for electrical stimulation alone had been demonstrated, under standardized conditions. Previously single-channel strategies had only shown a small improvement when electrical stimulation was used as a lip reading aid, but no speech understanding for electrical stimulation alone.

As a result Clark went on to operate on a second patient who had been deaf for 17 years. He was able to show that the speech coding strategy was not unique to one person’s brain response patterns, and that the memory for speech sounds could persist for many years after the person became deaf.

Industrial Development -1979

Clark recognized the importance of the research being developed industrially to benefit many people, and he played a key role in facilitating the negotiations with the pacemaker firm Telectronics. The Australian government underwrote its industrial development. By August 1981 the company was listed on the Australian stock market as Nucleus Limited, which subsequently floated the subsidiary Cochlear Pty Ltd. This company was responsible for conducting the commercial development, and did so through a close relationship with the research led by Clark.

The successful development of the cochlear implant was confirmed when it gained approval from the Food and Drug Administration (FDA) in the United States. In 1982 Clark supervised the initial clinical studies mandated by the agency, and in 1985 after a world trial the FDA granted approval for the cochlear implant for adults 18 and over who had hearing before going deaf. It thus became the first multi-channel cochlear system to be approved as safe and effective by the FDA or any health regulatory body for giving speech understanding both with lip reading and for electrical stimulation alone in people who had hearing before going deaf.

Research

Clark led the research to discover how speech was coded by the brain through electrical stimulation of the auditory nerve, and how he could improve the strategy so that most deaf people could achieve near perfect speech perception. Clark and Tong discovered that the frequency glides of importance for coding the plosive sounds in speech e.g. /b/, /d/, /g/, are best coded by changes in place of stimulation rather than rate of stimulation, over the short durations required for these consonants. They discovered that rate of stimulation was perceived as voicing in the appropriate speech context, and voicing was recognized for rate of stimulation across the spatial frequency channels. They discovered that electrical stimulation of two electrodes could be perceived with two components, but were fused into one speech percept. This indicated that a speech processor that presented two or more formants or frequency bands, instead of one, should provide better speech perception. This was shown to be the case by Clark and team. As a result of these and later related discoveries by Clark and team a majority of severely-to-profoundly deaf people who have had hearing before going deaf can achieve approximately 60% speech understanding without help from lipreading, and nearly 100% understanding with the aid of lipreading. Clark also discovered that his formant extraction scheme provided excellent speech understanding for an adult using a tonal language e.g. Mandarin. However, hearing speech in noise can be difficult and the sounds of music are not ideal. Research is needed to improve these outcomes.

Research into speech perception in deaf children

In 1985, Clark as the surgeon-in-charge performed the cochlear implant surgery on the first children along with Drs Pyman and Webb. The first child was 10 years old and the second was 5 years old. From 1985 to 1990 Clark and the members of his Cochlear Implant Clinic at the Eye and Ear Hospital in Melbourne, followed by other clinics world wide, found that the formant extraction speech coding strategies developed by Clark and team resulted in up to 60% of children being able to understand significant numbers of words and sentences with electrical stimulation alone without help from lipreading. With a strategy that also extracted a band of high frequencies there were increased numbers of children with improved speech perception, speech production and language scores.

In 1990 the FDA announced that the 22-channel cochlear implant was safe and effective in enabling deaf children from ages two through 17 years to understand speech both with and without lipreading. It was the first cochlear implant to be approved by any world regulatory body for deaf children. It is thus the first major advance helping severely-to-profoundly deaf children to communicate in the last 200 years since Sign Language of the Deaf was developed by l’Abeé de l’Épée at the Paris Deaf School and Speech Reading by Heineke in Germany.

Further research led by Clark’s team showed there was a trend for better speech perception the younger the child. For this reason, Clark undertook additional biological safety research to ensure that there was no adverse effect from head growth, and that pneumococcal middle ear infection could be prevented from spreading to the cochlea to help avoid the risk of meningitis. It was only after the safety studies were complete, and showed minimal risk that Clark carried out operations on young children.

Clark with Dowell and colleagues then found that children operated on under four years of age have phoneme, word and sentence recognition scores that are similar to those for deaf adults who had hearing before going deaf. At the same time Clark and Busby discovered that more basic perception skills that included the ability to discriminate electrode place of stimulation were worse if there was a long period of hearing loss, or the child was implanted at an older age. The research also suggested that exposure to sound or electrical stimulation during the “plastic” phase of brain development is required for this perceptual skill to develop, and this is important for good speech perception.

In addition, it was shown that the ability of children to rank the pitch of electrodes with the electrode place of stimulation (rather than discriminate electrode place) is an important requirement for speech perception. But not all children who could rank electrode pitch had good speech perception suggesting the development of neural connectivity for place discrimination or pitch ranking is not the only factor for learning speech. Other factors could be temporal processing or the development of language.

The Benefits of Binaural Hearing with an Implant in Each Ear or an Implant in One Ear and a Hearing Aid in the Other -1995.

Once Clark established the benefit of a cochlear implant in one ear he commenced research to determine the value of bilateral implants, and an implant in one ear and a hearing aid in the other. His aim was to reproduce the benefits of two ears. These benefits are: a) the ability to localize the direction of a sound (due to differences in the intensity as well as the time of arrival and phase of the sound at each ear); b) hearing speech in noise in each ear due to central neural mechanisms that partially remove the noise, but not the signal (squelch effect or binaural release from masking), c) hearing speech on one side with competing noise in the opposite ear (the head shadow effect) d) loudness summation. He first undertook psychophysical studies with colleague van Hoesel in 1995. They showed that interaural intensity differences could be readily detected to give good sound localization, but differences in the interaural time of stimulation were more poorly detected. When sound localization was tested with a series of free-field speakers the average detection was 15.50 compared to 10-20 for normal hearing. When the cues were isolated, the interaural temporal differences for electrical stimulation were similar for sound at 50 pulses/s (150 μs), but not at higher rates. The average interaural intensity difference perceived was 0.3 decibels(dB) for electrical stimulation, and this was approximately three times that for normal hearing.

To investigate the head shadow as well as the “squelch” effect, it was necessary to present the noise separated in space from speech. The head acts as an acoustic barrier that attenuates the signal on the far side of the head compared to the near side. The effect is greater for high frequencies, and is approximately 7 dB in the speech frequency range. Firstly, the signal-to-noise ratio was determined for the reception of speech with the speech and noise presented from directly in front. The noise source was then separated and moved to say the left ear and the signal-to-noise ratio adjusted for speech reception. It would then be expected that on the left side the noise would have to be reduced when testing the left ear to achieve the same speech reception threshold. When testing the right side, the speech signal intensity could be reduced to achieve the same speech reception threshold. In the binaural case it could be reduced even further suggesting that not only was there a head shadow effect, but a “squelch” effect. When the data on four subjects were analyzed there was a very significant head shadow effect of 4-5 dB. A “squelch” effect was marginally significant at 1-2 dB.

The University of Melbourne’s Department of Otolaryngology & The Bionic Ear Institute

In 1970 Clark was appointed as the Foundation Professor of Otolaryngology (Ear, Nose, and Throat Surgery) at the University of Melbourne, and then in 2000 he was made one of the first Laureate Professors at the University for his international recognition of scientific achievement. He held this position till he retired in 2004. He led most of the pioneering cochlear implant research while Head of the Department of Otolaryngology. His research was funded initially by an appeal through a Telethon, and then a Public Interest Grant from the Australian government. His ongoing research to understand the functioning and improve the cochlear implant was through his grants from the National Health and Medical Research Council of Australia, the Australian Research Council, The US National Institutes of Health, and The Cooperative Research Centre program. He was also able to coordinate the basic with clinical studies as the head of cochlear implant clinic at the Eye and Ear Hospital (the first public hospital based cochlear implant clinic in the world). In 1983 the Bionic Ear Institute was founded by Clark, as an independent, non-profit, medical research organization. The goal of the Bionic Ear Institute was: “to give deaf children and adults the opportunity to participate as fully as possible in the hearing world and to find new ways to restore brain function”. It has been an important means of supporting Clark’s efforts to provide effective hearing for most deaf people through the bionic ear (multi-channel cochlear implant.

After 34 years as the Foundational Professor of Ear, Nose and Throat Surgery at the University of Melbourne, and 20 years as the Founding Director of the Bionic Ear Institute Clark retired from these positions. He was then appointed as the first Distinguished Professor at La Trobe University in Melbourne, and is involved in the development of the Graeme Clark Centre for Bionic Ear and Neurosensory Research. The centre is within the School of Psychological Science, and is coordinating research in neurophysiology, electrochemistry, materials science, psychology of speech and language, and signal processing. Its aim is to facilitate cross-disciplinary fundamental research, and its application to the development of treatments for hearing loss and other neurosensory disorders. In particular its aim is to develop bionic ears that provide high fidelity hearing for better perception and music appreciation.

Charity foundations

In 2002 The Graeme Clark Cochlear Scholarship Foundation was established in honor of Graeme Clark for his lifelong commitment to finding a solution for people with hearing loss, and his pioneering work in the field of cochlear implant technology. Awarded by Cochlear Limited, scholarships are presented to cochlear implant recipients around the world to help defray the costs of their higher education consisting of financial assistance towards a college degree at an accredited university for up to four years).

In recognition of Clark’s contributions to the welfare of deaf people, The Graeme Clark Charitable Foundation, a charitable foundation has been established to firstly enable individuals with deafness and other sensory disorders develop their potential through appropriate biomedical, technological and educational measures.

The Graeme Clark Centre for Innovation in the Sciences-2009

The Scots College, a private school in Sydney, has built a new science building named the Graeme Clark Centre for Innovation in the Sciences. It is a state-of-the-art facility, designed to promote in the hearts and minds of students a love and appreciation of the sciences so they may make a key contribution to Australia’s future.

Selected Honours

2007 Australian Father of the Year award

2006 Senior Australian of the Year

2005 National Australia Day Council, Australian Achiever’s Award

1999 Companion of the Order of Australia (AC)

1997 Officer of the Order of Australia (AO)

1985 Prime Minister's Prize for Science

Academic

2004 Fellow of the Royal Society of London

2003 Honorary Fellow, The Royal Society of Medicine, London

1998 Fellow of the Australian Academy of Science

Personal Named Distinctions

2008 The Graeme Clark Centre for “Innovation in the Sciences” at The Scots College, (a leading secondary school), Sydney

2008 The Graeme Clark Foundation, (The Graeme Clark Foundation was established to help disadvantaged people with sensory disorders develop their true potential. It also aims to give opportunities to talented scientists to develop their research to restore vital senses).

2008 The Inaugural Graeme Clark Research Outcomes Forum. (the Australian Research Council’s Forum highlights the ways in which quality research can translate into important benefits for the community). The Inaugural Keynote address was given by Graeme Clark.

2008 The Graeme Clark Annual Oration, for Australia’s Information and Communications Technology (ICT) Research Centre of Excellence for Life Sciences, The Inaugural Oration was given by Graeme Clark

2003-04 The Graeme Clark Cochlear Implant Workshop for Japanese Surgeons organized by the Cooperative Research Centre for Cochlear Implant and Hearing Aid Innovation

2002 The Graeme Clark Cochlear Scholarship, awarded annually, was established in Australia and the United States to assist people with cochlear implants to undertake tertiary studies.

2002 The Graeme Clark Room, the Ear Foundation, Nottingham, UK

Academic Leadership

1984-2005 Founder and Director, The Bionic Ear Institute, East Melbourne, Australia

1970-2004 Foundation Professor of Otolaryngology and Chairman, Department of Otolaryngology, The University of Melbourne, Australia

1988-1996 Director, The Australian Research Council’s Special Research Centre the Human Communication Research Centre, East Melbourne, Australia

A Selected Bibliography of the Most Important Publications

Books

Clark GM. (2003) Cochlear Implants: Fundamentals and Applications. Springer-Verlag, New York. (The first textbook on the cochlear implant, a major 800 page work written solely by Clark)

Clark GM. (2000) Sounds from Silence. Allen & Unwin, Sydney. (Clark’s Autobiography)

Patents

Hearing Prosthesis - Improvements in Prosthesis

Inventors: G.M. Clark, J. Patrick, I. Forster, Y.C. Tong, R.C. Black. (1977)

Countries & Patent Nos.: Australia - 519,851 (3.11.77); Europe - 78.300567 (France, West Germany, The Netherlands, United Kingdom); Denmark - 78.4902; Japan - 1529582; U.S.A. - 4,267,410; Canada - 1,100,189.

(The first patent of a receiver-stimulator designed to stimulate the auditory nerve and for speech understanding)

Hearing Prosthesis - Speech Processor

Inventors: G.M. Clark, J. Patrick, J. Millar, P.M. Seligman, Y.C. Tong (1979)

Countries & Patent Nos.: Australia - 535,489 (19.12.79); Europe - 80901001.0 (U.K, West Germany, France, Sweden, Italy, The Netherlands); Japan - Application No. 55-501189; U.S.A. - 4,441,202; Canada - 1,165,884.

(The first patent of the second formant/voicing speech processor for speech recognition in profoundly deaf people)

Improvements in Speech Processor, Inventors

G.M. Clark, J. Patrick, J. Millar, P.M. Seligman, Y.C. Tong (1980)

Countries & Patent No.: Australia - 541,248; Canada - 391,699; Denmark - 549,881; Europe - 813,058,377; Japan - 19,874,081; U.S.A. - 4,515,158.

(The first patent for the second and first formant/voicing speech processor)

Improved Sound Processor for Cochlear Implants

DB Grayden, GM Clark (2006) (differential rate speech processor)

Countries & Patent No.: DE 60025735

Emphasis of Short Duration Transient Speech Features, Inventors

A Vandali and GM Clark (Transient Emphasis speech processor)

Countries & patent No: US 7444280, (28.10.2008)

See also

• Cochlear Limited

External links

1."Professor Graeme Clark." 06 May 2007. 8 Nov 2008 http://www.quazen.com/Reference/Biography/Professor-Graeme-Clark-.24425

2.Sounds from Silence: Autobiography by Graeme Clark http://books.google.com/books?hl=en&id=qeuUoRlvJOYC&dq=sounds+from+silence:+graeme+clark&printsec=frontcover&source=web&ots=XJvVi1I8Qu&sig=gkccUH3AMnEtqUFOG2zWVGib7os&sa=X&oi=book_result&resnum=1&ct=result

3.Cochlear Implants : Fundamentals and Applications: by Graeme Clark: (written by the “father” of the multiple-channel cochlear implant, this comprehensive text and reference gives and account of the fundamental principles underlying cochlear implants and their clinical application. It thus discusses work in all relevant disciplines. http://catalogue.nla.gov.au/Record/1009944

4.The University of Melbourne Find an Expert (Graeme Clark): http://www.findanexpert.unimelb.edu.au/researcher/person15904.html

5.National Library ASAP entry: http://www.asap.unimelb.edu.au/bsparcs/archives/P001420a.htm

6.National Library Graeme Clark papers: http://www.nla.gov.au/ms/findaids/8696list.html

7.National Library Pandora Graeme Clark Web archive: http://pandora-search.nla.gov.au/apps/textsearch/action/searchget?query=Graeme+Clark&x=38&y=4

8.Graeme Clark research and development process: http://www.powerhousemuseum.com/hsc/cochlear/research.htm

9.About Graeme Clark – Cochlear: http://www.cochlear.com.au/Corp/Company/179.asp

10.Graeme Clark Cochlear Scholarship: http://www.cochlear.com.au/Corp/Press/236.asp and http://www.cochlear.com.au/Community/600.asp and http://www.cochlearamericas.com/Support/168.asp

11."The Bionic Ear Institute." People in Our Group. 8 Nov 2008 http://www.bionicear.org/people/clarkg/

12.Senior Australian of the Year award: http://www.australianoftheyear.org.au/pages/page116.asp

13.Boyer lectures (Graeme Clark): http://catalogue.nla.gov.au/Record/4274036

14."Boyer Lectures." ABC Radio National. 8 Nov 2008 http://www.abconline.net.au/rn/boyerlectures/stories/2007/about/

15.The Graeme Clark Charitable Foundation: http://graemeclarkfoundation.org/default.htm

16.Inaugural Graeme Clark Oration: http://ict4lifesciences.org.au/inaugural-graeme-clark-oration.html and

17.Inaugural Graeme Clark Oration http://nicta.com.au/__data/assets/pdf_file/0017/18035/NICTA_News_Iss16_Final_Art.pdf

18.Graeme Clark Forum Australian Research Council, Canberra: http://www.research-outcomes.com.au/article.php?article=5,101

19.Graeme Clark Centre for Innovation in the Sciences- Scots College, Sydney: http://www.tsc.nsw.edu.au/docs/user/1324.pdf

20.The Graeme Clark Centre for Bionic and Neurosensory Research: http://www.latrobe/news/articles/2009/article/bionic-ear-launch