Аустралиялық отоларинголог ғалымы Грэм Милборн Кларк туралы

Australian professor of otolaryngology

Graeme Milbourne Clark (born 16 August 1935) is an Australian Professor of Otolaryngology at the University of Melbourne. Worked in ENT surgery, electronics and speech science contributed towards the development of the multiple channel cochlear implant. His invention was later marketed by Cochlear Limited.

Clark was born in Camden, New South Wales, to parents Colin and Dorothy Clark. He has one younger sister. Clark was educated at Carey Baptist Grammar School, where he was later honoured with the ‘Carey Medal’ in 1997. Clark was educated at The Scots College and studied medicine at Sydney University. He specialized 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 returned to Australia where he became a Fellow of the Royal Australian 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 learn more about speech science.

Clark hypothesized 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 stimulation on single cells and groups of cells in the auditory brain stem response, the centre where frequency discrimination is first decoded. 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. He achieved a breakthrough during a vacation at the beach; he conceptualized using a seashell to replicate the human cochlea, and grass blades (which were flexible at the tip and gradually increasing in stiffness) to represent the electrodes. Clark showed that the electrode bundle had to be free fitting, and the wires needed to be terminated with circumferential bands to reduce friction against the outer wall of the cochlea; as to make it easier to pass the required distance. The bands had to be wide enough to minimize the charge density of the electric current for safety, but narrow enough for localized stimulation of the nerve fibres for the place coding of frequency. In order to address issues about the safety of the device, Clark conducted experiments to show that there was 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 first cochlear implant was invented and developed by Dr. William F. House. House's device was a single electrode configuration, compared to the multiple electrode device developed by Clark. Clark's 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. Less than one year later, a second patient was implanted. George Watson, an Australian World War II veteran, had lost his hearing after a bomb blast thirteen years earlier. An audiologist working on Clark's team at the time described the team's first two patients as, "guys who'd put up with anything and continue to keep coming in and support the work.". After successfully completing the surgery in 1978, with his post doctoral colleague, Yit Chow Tong, Clark discovered 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 (50 pulses/sec) was perceived as a pitch of the same frequency, but at rates above 200 pulses/sec, 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 Hz is required for speech understanding, so Clark emphasized early in the development of his 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. At the end of 1978, Clark and Tong made the discovery that 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. in December 1978, Clark arranged that his audiologist present open set words to his first patient, who was able to identify several correctly. 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. In 1982 Clark supervised the initial clinical studies mandated by the Food and Drug Administration (FDA) and in 1985, after a world trial, the FDA granted approval for his multi channel 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 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. After a detailed analysis of results the FDA announced in 1990 that the 22 channel cochlear implant was safe and effective for deaf children from two to 17 years of age in understanding speech both with and without lip reading. 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 worldwide, 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 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 until he retired in 2004. He led 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 Center program. 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". The Bionic Ear Institute renamed itself the Bionics Institute in 2011 due to an expansion of its aims to not just improve the bionic ear, but to develop a bionic eye and devices capable of deep brain stimulation.

In 2002 The Graeme Clark Cochlear Scholarship Foundation was established in honour 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.