There’s a lot of talk about a coming future of ‘bionic’ devices, aiding those with sensory and motor disabilities.
In reality ‘bionic’ sensory devices have already been with us for over 30 years in hundreds of thousands of people. The cochlear implant is a ‘bonic ear’ that enables many deaf people to hear.
They’ve advanced to the point that even tiny kids get them now.
It’s great to watch videos of cochlear implant switch-ons. (You can view some in the Switching on section below.)
The idea of the cochlear implant is remarkable, really.
A semi-circular cut is made behind the ear. A wire is threaded into the cochlear, the fluid-filled spiral-shaped organ in our inner ear lined with hair cells. The wire from the device sends electronic signals to the auditory nerve that the wearer learns to recognise as sound.
The wire leads from a small unit that is placed sealed under the skin. The person wears a device looking like a behind-the-ear hearing aid that is wired to a magnet that is placed on the skin above the internal unit, like in the infant above.
The external magnet is attracted to the internal unit, holding it in place, and the signal is transmitted through the skin as a radio frequency signal that is received by an induction loop in the internal device. The internal device is powered by this transmission.
There is no wire through the skin, as some of the early (single-channel) devices had — these were prone to being a route for infection, one of the many challenges overcome in developing the cochlear implant.
The hearing aid unit has the usual microphones, battery and a digital signal processing chip, that transforms the original microphone signal according to the parameters set by the audiologist as they adapt the device to the wearer. It isn’t a case of instant speech recognition as the device is turned on, but a process of learning to associate the signals with sounds.
The electrode inserted into the cochlear has several wires, or channels that aim to replicate the frequency-to-place information the cochlear provides to the auditory nerve. In this short video Dr. Douglas Backous, Medical Director of the Center for Hearing and Skull Base Surgery explains what a cochlear implant is,
Cochlear implants are still mostly implanted into one ear, but there is an increased trend to implant both ears giving bi-aural hearing that benefits the wearer.
In New Zealand cochlear implants are funded through Ministry of Health, prioritised to children. A brief introduction is also available on the Hearing Association of NZ cochlear implant information card (PDF file).
This video offers a breakdown of the components of a typical cochlear implant,
This year’s Lasker-DeBakey Clinical Medical Research Award was awarded to Ingeborg Hochmair, Graeme Clark, and Blake Wilson for their work developing the cochlear implant. It‘s one measure of the cachet of these prizes that 83 Lasker awardees have gone on to win Nobel Prizes.
There’s an excellent brief account of main players who developed the modern cochlear implant in an open-access piece for The Lancet, including Dr. House who died last year. (The reference to the modern cochlear implant is no doubt to distinguish the more successful multi-channel devices that are now used and House’s earlier single-channel device.)
(An historic aside – a 1974 video from the House Ear Institute.)
It’s good to see recognition of Wilson’s speech processing work in the Lasker-DeBakey Clinical Medical Research Award. (Compare this, for example, with the wikipedia entry for the cochlear implant, which at the time of writing doesn’t mention him by name at all although it mentions that “the signal processing algorithm is also another important block”. Presumably that will be put right with his name being associated with this award. It is, perhaps another useful reminder of the limitations of wikipedia.)
Cochlear implants are a fine example of how research draws on skills from disparate sources.
Developing these devices draws on a mix of audiological knowledge, neuroscience and anatomy, surgery techniques, engineering hardware (on several levels), finding the best way of delivering the electrical signals so that they might be perceived by the patient as speech and so on.
Switching on (and parents’ thoughts)
Videos of cochlear implant switch-ons are popular on YouTube. You could spend hours viewing them. I’ve selected a few below. (I can’t show some, like how young Allie holds the plastic coin as if it is sending her the sounds, as some people have chosen to disable embedding. Similarly I would like to have offered some parents’ views as they provide a different perspective.) The first has over 19 million views! –
This woman tries her hearing playing a xylophone after her CI activation:
Some babies, like Solomon, understandably react with surprise and confusion:
This 8 month old baby is way too adorable not to include:
This is a segment of the New Zealand current affairs program, Campbell Live (from 2007?)
I’m offering Annabelle’s activation for a little balance as it’s easy to think of CIs as ‘instant’ successes:
A titbit: in New Zealand there are three official languages, English, Maori and NZ Sign Language (NZSL).
1. As someone whose hearing loss is much more pronounced on one side compared to the other I can (anecdotally) testify to the impact of this, especially in noisier settings like most social situations. Even small gatherings quickly become surprisingly complex to follow. (Most deaf or hard-of-hearing people need lip-reading to help ‘fill in’ the portions where other noise dominates over the person they are trying to listen to.)
2. The Lasker Foundation offers four awards recognising “major advances in the understanding, diagnosis, treatment, cure, and prevention of human disease”. The awards cover basic science, clinical medical research, an achievement in medical science award and a public service award. It’s often said that Lasker Awards signal possible future Nobel Prizes and that’s been the case for 83 of the Lasker awardees thus far.
3. Although House is attributed with the development of the first CIs, wikipedia gives an unsupported (“citation needed”) account of Djourno and Eyriès developing a CI in the mid 1950s,
The first attempt to develop a clinical CI was in 1957 by Djourno and Eyriès. A recipient was implanted with a single channel device. Unprocessed sounds were transmitted via a pair of solenoid-like coils. The link was therefore transcutaneous; it did not require a break in the skin after implantation. This device failed after a short time and another device was implanted. After this second device failed, Eyriès refused to implant a third device. He urged Djourno to collaborate with an industry partner to build a more reliable device. Djourno refused because he believed that academia should not be tainted by commerce. Djourno found another surgeon, Roger Maspétiol, who implanted a second patient in 1958. Although these recipients were unable to understand speech with the device alone, it helped with lipreading by providing the rhythm of the speech.
5. It can be an useful starting point, but you need to verify claims and, as in this case, there can be missing material that is relevant.
6. As you might expect there is a lot of research and development on these devices and the brief accounts on-line make for fascinating reading. There is, apparently, work trialing the use of fibre optics to stimulate the auditory nerve and entirely internal CIs, for example. (It’s another example of that thing that if you had endless time you’d read all sorts of things, but the reality is each niche area has it’s large volume of background to absorb before you have an in-depth appreciation of developments.)
7. I have to admit I find this frustrating and I’m left wondering what the benefit to blocking embedding these particular videos are.
There is a large literature on cochlear implants, both academic and for those who just want to read personal accounts or a less formal account. I have two minds about offering those listed below as they are now fairly old (and there are likely to be better books available), but I hope they encourage some readers to try their local libraries. The ones listed are just what happen to be on my shelves. (Aside from general interest, for a while I toyed with taking up computational biology aspects of deafness as an alternative research area.)
Sounds from Silence: Graeme Clark and the Bionic Ear story.
Professor Graeme Clark
ISBN 1 86508 302 X, Allen & Unwin, 2000.
This is an autobiographical account of Prof. Clark’s work on the Australian cochlear implant device.
Wired for sound: a journey in hearing
ISBN 1-895579-32-5, Trifolium Books Inc., 1998.
This personal account of losing hearing, then later regaining (some) hearing is now 15 years old — perhaps a testimony to how long cochlear implants have been around. There are many newer personal accounts and this one is very likely out of print.
ISBN 0 330 32090 4, Picador, 1991.
Oliver Sacks is, of course, renown in science communication circles for his personable accounts of neurological conditions. Here is delves into deafness. The ‘Seeing voices’ of the title refers to either lip-reading or sign language – communication by sight rather than sound. (This reminds me of something I’ve long meant to blog, that native sign language is processed directly in the language area of the brain (Broca’s area), despite that the input source is different to most people, who hear language.) Sack’s book tends to deal more with the capital-D deaf community. (There’s a political distinction between the Deaf and the deaf, maddening as it might seem to outsiders.)
Deaf young people and their families
Susan Gregory, Juliet Bishop and Lesley Sheldon
ISBN 0 521 42998 6, Cambridge University Press, 1995.
This book is a personal choice – it presents the results of a longitudal study of deaf children growing up over an 18 year period.
Other articles on Code for life: