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		Graeme M. Clark AC FAA FTSE FRS FAAS FAIMBE MB, BS, MS, PhD (Sydney), FRCS (Edinburgh), FRCS (England), FRACS Hon. MD (Hannover), Hon. MD (Sydney), Hon. DSc (Wollongong), Hon. DEng (CYC Taiwan), Hon. LLD (Monash), Hon. FAudSA, Hon. FRCS (England) Founder and Director Emeritus, The Bionic Ear Institute Laureate Professor Emeritus, The University of Melbourne Professor, The University of Wollongong The Centre for Clinical Neuroscience and Neurological Research St. Vincent’s Hospital P.O. Box 2900, Melbourne VIC 3065, Australia Tel:  +61 3 9288 3564, Fax: +61 3 9288 3350 E-mail: gclark@bionicear.org Professor Graeme Clark, who was born in Camden, New South Wales, pioneered the multiple-channel cochlear implant (bionic ear). It is the first cochlear implant to reliably give speech understanding to severely-to-profoundly deaf people, as well as spoken language to children born deaf. These people can thus communicate in a world of sound. In so doing it became the first neural prosthesis to effectively and safely bring electronic technology into a direct physiological relationship with the brain and human consciousness. In addition, Clark showed the multiple-channel implant was safe and had no greater risk of meningitis than for the general community, if appropriately designed. He also developed surgical and diagnostic procedures that were the basis for its regular clinical use. Graeme Clark was motivated to embark on his scientific journey by his father’s deafness, as well as being inspired by the life and work of Louis Pasteur. He came to the view that hearing, particularly for speech, might be reproduced in deaf people if the damaged or undeveloped inner ear was bypassed and the auditory nerve stimulated electrically to partly reproduce the coding of sound. Clark met considerable opposition in reaching his goal as most scientists thought speech sounds could not be reproduced with electrical stimulation of the auditory nerve because the cochlea (inner ear) (fig.1) is innervated by 10,000 to 20,000 neurons in a complex manner (fig.2). In the 1960s the general scientific climate of opinion is typified by this statement by a leading scientist who said that: “Direct stimulation of the auditory nerve fibres with resultant perception of speech was not feasible”. Clark’s first research was at the University of Sydney from 1967 to 1969, and indicated that a cochlear implant with single-channel (electrode) stimulation of the auditory nerves in the inner ear to reproduce the temporal coding of frequency would not lead to speech understanding in deaf people. Multiple-channel stimulation of different frequency regions of the cochlea on a place coding basis would be required (fig.3). Then Clark initiated and led the research that showed multiple-channel electrical stimulation of the auditory nerves with electrodes inserted into the cochlea was safe and effective. Clark’s biomedical research first demonstrated that an electrode bundle with graded stiffness would pass without injury around the tightening spiral of the cochlea to the speech frequency region. He first established this principle on a sea shell which is a replica of the human cochlea using blades of grass that were flexible at the tip and gradually increasing in stiffness (fig.4). This finding was subsequently confirmed on both human temporal bones and with mathematical modelling studies of the mechanical properties of the electrode bundle. He also showed that the bundle had to be free-fitting and the electrode wires terminated with circumferential bands to reduce friction against the outer wall of the cochlea to make it easier to pass the required distance. The width of the bands had to be wide enough to minimize the charge density of the electrical current to make it electrically safe, but narrow enough for localized stimulation of nerve fibres for the place coding of frequency. Furthermore, his animal experimental studies demonstrated there was minimal risk of meningitis from middle ear infection if a fibrous tissue sheath grew around the electrode bundle (fig.4). The development of the sheath was facilitated with a connective tissue graft from the person’s own body placed around the electrode bundle where it entered the cochlea. The prototype cochlear implant was initially implanted at the Royal Victorian Eye and Ear Hospital on 1st August 1978 in a laminar flow of filtered air to reduce the risk of infection (fig.5). Professor Graeme Clark next discovered together with Dr Yit Chow Tong that subjects could perceive rate of stimulation as pitch, but only discriminate changes in rate of stimulation up to about 300 pulses/s, which is just high enough to discriminate voiced sounds such as /b/ from /p/. Place of stimulation had a different quality of sound, and was not perceived as pitch but as timbre. However, this proved appropriate for discriminating different sites of stimulation, and thus the place coding of frequency (fig.6). The cochlear implant was nevertheless a “bottle-neck” at the interface between the world of sound and the auditory central nervous system (fig.6). Clark and colleagues then discovered that a multiple-channel cochlear implant with a speech processing strategy that selects frequencies (formants) of special importance for intelligibility (in particular the second and then the first formants) could transmit information through the "bottle-neck" (fig.7), and provide significant understanding of speech for severely-to-profoundly deaf children and adults, and good spoken language for deaf children. Formant frequencies are due to resonances from changes in the shape of the vocal tract just as the length of organ pipes determines its resonant frequency. The energy for the formants was used to stimulate electrodes in the inner ear that lie near the appropriate frequency regions. In addition the voicing frequency determined the rate of stimulation for each electrode (fig.7). Graeme Clark not only led the research to develop the multiple-channel cochlear implant (fig.8), but personally played the key role in seeking its industrial development. He also took responsibility for and supervised the initial clinical studies required for the US Food and Drug Administration (FDA). Approval of the implant was given by the FDA in 1985 for adults who had hearing before going deaf. It was the first multiple-channel cochlear implant to be approved for adults who had hearing before going deaf. His personal efforts from 1967 to 1985 and those of government and industry made the implant developed by Cochlear a commercial reality. This story is outlined in: “Sounds from Silence: Graeme Clark and the Bionic Ear Story” published by Allen and Unwin, 2000. Clark’s continued research, and clinical skills then next led to the trial of the multi-channel implant for the FDA for severely-to-profoundly deaf children. This commenced in 1985 when Clark as the surgeon-in-charge operated on the first children at the Eye and Ear Hospital in Melbourne. Then, as principal investigator for a National Health and Medical Research Council program grant and Head of an Australian Research Council Centre of Excellence, he led the research that showed the benefit of the multi-channel implant for young children and what factors resulted in the best speech results. The world trial was then extended to major centres and it was approved as safe and effective for children over two years of age by the FDA. This made it the first cochlear implant of any type to be approved by a world regulatory body, and it thus became the first major advance in helping severely-to-profoundly deaf children to communicate in the last 200 years since Sign Language of the Deaf was introduced at the Paris Deaf School. Further research that Graeme Clark initiated has demonstrated that bilateral and bimodal cochlear implants could enable people with an aid in one ear and an implant in the other as well as people with bilateral cochlear implants to localize sound and hear more effectively in noise. Clark is continuing his research in Nano-bionics through an Australian Research Council’s centre of excellence to develop an electrode interface to the auditory system that could achieve high fidelity sound. This requires the use of intelligent polymers, nerve growth factors and carbon nanotubes. He is extending his research in Electrophonics to use electrical stimulation of the cochlea to excite both residual hair cells in the organ of Corti and auditory nerve fibres. His research in Mechatronics is to study how to produce a “steerable” electrode to place in the optimal location for these strategies. Clark is also expanding his research in auditory neuroscience to develop the discipline of Medical Bionics. This incudes research for infection control with implanted devices, the correction of nerve and spinal cord injuries, and the treatment of drug resistant epilepsy. In addition, Clark has played a key role in the development of the Automatic Brainwave Audiometer, the first method for objective accurate measurement of hearing thresholds for low and high frequencies in infants and young children, and the “Tickle Talker”, a device enabling deaf children to understand speech through electro-tactile stimulation of the nerves of the fingers. Australian Research Council's Graeme Clark Research Outcomes Forum (pdf) Frequently Asked Questions (pdf) Summary of Graeme Clark's Cochlear Implant Discoveries Curriculum Vitae 20 Most Significant Peer-reviewed Research Papers Complete list of Scientific Publications Citations Research Funding Patents Illustrated Lectures: A partnership in Research Leading the Bionic Ear and Beyond 2008: The ICT Life Sciences Graeme Clark Oration 2008, Melbourne, Australia The cochlear implant: a model for bio-medical innovation and industrial development, Australian Research Council's Graeme Clark Research Outcomes Forum 2008, Canberra, Australia The multiple – channel cochlear implant: The sensory interface between the world of sound and human consciousness. Graeme Clark, A principal speaker, Frontiers in Medicine at Nobel Forum: Cochlear Implants from Bench to Bedside, Karolinska Institutet. Speech understanding with the multiple – channel cochlear implant: interfacing electronic technology to human consciousness. Plenary address, Interspeech 2005 – Eurospeech conference, Lisbon Cochlear implants: climbing new mountains. The Graham Fraser Memorial Lecture, The Royal Society of Medicine, London, February, 2001 Recent Publications: The multiple-channel cochlear implant: the interface between sound and the central nervous system for hearing, speech, and language in deaf people - a personal perspective, Graeme M. Clark, Philosophical Transactions of the Royal Society B 2006. (1.1Mb pdf) Cochlear Implants: Fundamentals and Applications, Graeme Clark, AIP Series in Modern Acoustics and Signal Processing, Springer-Verlag, New York, 2003. ISBN 0-387-95583-6
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