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|The origins : Volta's experimentation
Interest in stimulating hearing with electricity began in the 18th country with Count Volta, an Italian physicist who developed the electric battery. In 1800, he connected batteries to two metal rods that he inserted in his ears. He described that he received a 'jolt in the head' and then a sound 'a kind of crackling, jerking or bubbling as if some dough or thick stuff was boiling' (Epstein:1989: 34). Not surprisingly, it was quite uncomfortable and Volat did not repeat the experiment !
Fifty years after Volta, a Frenchman, Duchenne of Boulogne, tried using an alternating current to stimulate his hearing and heard what he described as a sound like an insect trapped between a glass pane and a curtain.
Stimulating the auditory nerve
The first direct stimulation of the auditory nerve in a human was performed during an operation by Lundberg in 1950 – the patient became aware of noise. In 1957, Djourno and Eyries implanted an electrode attached to an induction coil in the head of a deaf person. They were able to transmit a signal to the electrode via a radio antenna on the outside of the body. The person heard sounds resembling the chirping of a grasshopper or cricket. He was also able to recognise simple words like mama, papa, and allo. This experiment inspired many investigators about the possibilities of using implanted prostheses to enable deaf people to hear.
An important trial with multiple electrodes stimulating the cochlea was successfully performed by American surgeons, John M Doyle, William F House and an electronic engineer, James Doyle. In 1964 Dr F Blair Simmons of Stanford University Medical School, with his team, implanted six electrodes with success. The recipient could recognise simple tunes. This research increased the knowledge of how the brain coded frequencies and responded to electrical stimulation.
There was much more work done in the 1960s and 70s to increase knowledge of how the cochlea functions and how speech is perceived. Studies led to the idea that the best way for a profoundly deaf person to hear speech is by stimulating the auditory nerve using a multiple electrode device. Research in electrical and mechanical technologies, progress in materials technology and experiments with pacemaker implants also increased the opportunities to advance with cochlear implants.
For more information on hearing experiments: http://www.medoto.unimelb.edu.au/info/history2.htm
Cochlear: an Australian innovation success
An Australian, Graeme Clark, was greatly inspired by Dr F Blair Simmon's work with multiple electrode implants. Graeme Clark's father was hearing impaired, and had sensori-neural deafness. He was a pharmacist and often had to ask his customers to speak up about their medical problems, which embarrassed him and them. This background made Clark very aware of the deaf people's problems.
In 1967 Clark embarked on a long journey towards fulfilling his dream of helping deaf people hear the spoken word again. As a PhD student at the University of Sydney, Graeme Clark reviewed the available research to 'investigate whether a single or multiple-channel (electrode) cochlear implant would be possible for the management of a profound hearing loss.'
He believed that implants on humans should not be done until basic research on animals had solved some of the problems. For ten years his research into electrical stimulation of the auditory nerve via an implant into the cochlea struggled along on animal experiments and university grant funding.
Funding the project
In 1974 a telethon on Channel 10 in Melbourne generated enough funds to take his work to the prototype stage and in 1978 to test it in a human patient, Rod Saunders. The cochlear implant worked: Rod could perceive sound again.
This demonstration encouraged the federal government to finance commercialisation of the cochlear implant. The financing of the cochlear implant became a remarkably successful joint venture to manufacture and market the product. A three-way partnership was begun between researchers at the University of Melbourne, the Federal government and a medical equipment exporter called Nucleus. The researchers provided the scientific expertise, Nucleus contributed experience in making and selling advanced medical equipment and the government provided project management and over a million dollars in grants.
This partnership led to the formation of a string of Cochlear enterprises in the US, Japan and Switzerland including Cochlear Ltd in Australia. And permitted to Pr. Clark to build the first ear processor – quite big ! – for cochlear implant in 1980, followed by the first public release of cochlear implant in 1982, with the Nucleus® 22, which was a 22 channel implant.
By the early 1990s Cochlear Ltd was making a profit and Professor Clark was earning royalties.
Since then the Australian cochlear implant system has been used by over 30 000 people in 50 countries. It is the world's most widely used cochlear implant system.
In Australia, Cochlear Ltd design its products in accordance with the Implantable devices standard and the European Cochlear implant standard.
Features of the Nucleus® 22 Cochlear Implant System include:
- Internal implant with 22 channels for more stimulation. More channels give more flexibility in programming, more pitch information and improved hearing in noisy situations.
- SPEAK speech coding strategy, designed to improve speech comprehension, especially in noise.
- A long history of speech processor upgrades including the Spectra, a lightweight, powerful body worn speech processor and ESPrit 22, a compact, ear level speech processor. (Cochlear, 2001)
Nucleus® 24 Contour, introduced in 1999 uses a pre-curved electrode. The electrode is made with the curved shape of the cochlea, improving the sound quality and simplifying surgery. The design won the Australian Design Award™ of the Year 2000.
The Freedom ear processor followed in 2005, compatible with the inner implants presented supra, gave more flexibility to users by functioning either with rechargeable batteries or piles. It was also lighter than the Esprit 22, and had a little screen to see what hearing program is selected.
The new Nucleus® 5 had just been released in 2010, and seems to be a big technical improvement in the field of ear processors. To have a look on its detailed presentation, see on Cochlear Ltd site : Nucleus 5
Information source : Powerhousemuseum.com