The future of Cochlear Implants……..

April 15, 2010 at 12:17 pm | Posted in Cochlear Implants | 4 Comments
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Read this aloud and your inner ear, by itself, will be carrying out at least the equivalent of a billion floating-point operations per second, about the workload of a typical game console. The inner ear together with the brain can distinguish sounds that have intensities ranging over 120 decibels, from the roar of a jet engine to the rustle of a leaf, and it can pick out one conversation from among dozens in a crowded room. It is a feat no artificial system comes close to matching.

But what’s truly amazing is the neural system’s efficiency. Consuming about 50 watts, that game console throws off enough heat to bake a cookie, whereas the inner ear uses just 14 microwatts and could run for 15 years on one AA battery. If engineers could borrow nature’s tricks, maybe they could build faster, better, and smaller devices that don’t literally burn holes in our pockets. The idea, called neuromorphic engineering, has been around for 20 years, and its first fruits are finally approaching the market.

The likely first application is bionics–the use of devices implanted into the nervous system to help the deaf, blind, paralyzed, and others. There are two reasons for this choice: the biological inspiration crosses over to the application, and the premium on energy efficiency is particularly important.

Bionic ears are a case in point. Today’s device, called a cochlear implant, consists of an implanted electrode array; a bulky, power-hungry digital-signal processor worn outside the ear; and a wireless link that conveys data and power to the implanted electrodes. In the near future, these devices will be fully implanted inside the body so that deaf people will be indistinguishable from everyone else in both appearance and, we hope, ability to hear. In the past year, a lab at the Massachusetts Institute of Technology has completed work on a bionic-ear processor that does the job of the digital-signal processor, is small enough to be implanted, and could run on a 2-gram battery needing a wireless recharge only every two weeks [see illustration, “Mimicking the Ear“]. As the best batteries currently available can be recharged about 1000 times, this device is the first to permit 30-year operation without surgery to replace the battery.

Neuromorphic engineering and, more generally, biologically inspired electronics are still in their infancy, but practitioners have already accomplished amazing things. These include the attempt to understand biological systems, such as the retina of the human eye and the sonar systems of bats, by modeling them in microchips. Some of the lessons learned have been turned to practical purposes–for instance, applying the principles of vision in the housefly to the control of robotic motion and designing radio-frequency spectrum analyzers that mimic the architecture of the human inner ear. Some devices now measure oxygen saturation in the blood with sensors and processors inspired by the photoreceptors in our eyes; others employ pattern-recognition circuits that rely on the mix of analog and digital features found in the brain.

One of biology’s big power-saving secrets is that it relies on the physics of special-purpose structures, such as ears and eyes, to do a lot of analog computing. Ears, for example, are complex structures that by their inherent physics alone perform filtering, frequency-spectrum analysis, and signal compression–all before the signals are transmitted to the brain. Many of the initial insights into biology’s computing efficiency originated with Carver Mead, professor emeritus at the California Institute of Technology, in Pasadena–the founding father of neuromorphic engineering.

But ears, eyes, and even individual brain cells also have a digital aspect. Brain cells, or neurons, can be viewed as special-purpose analog-to-digital converters. They recognize particular patterns of voltage inputs from other neurons, integrate these signals in an analog manner, and then output a digital-like signal, a voltage spike (1) or its absence (0). Output spikes from one neuron act as inputs to the next neuron. And this simple process, amplified and repeated by billions of interconnected neurons, leads to movement, hearing, thought, and everything else under our brain’s control.

Analog devices in the ear, such as the eardrum and the cochlea, process sound. The ear then digitizes the processed sound signal by encoding it as spikes of voltage that travel down the auditory nerve to the brain, which interprets the spikes to distinguish a jazz tune from an oncoming train or a whisper. Because the ear has already done a great deal of analog computation on the sound, the information it provides the brain is more compact and far better suited than raw sound to human tasks, such as understanding what a child is whispering in a crowded movie theater. This scheme of low-power analog processing followed by digitization is one of the most important lessons biology has to teach designers of electronics.


Graham’s Sudden Sensorineural Hearing Loss Journey

January 27, 2010 at 10:21 pm | Posted in Cochlear Implants | 3 Comments
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My story starts around 10 years ago (Its been so long I cant remember exactly) when I woke up one morning and I couldn’t hear out of either ear.  I had a slight cold and assumed it was wax or congestion so popped off to the chemist.  I wasn’t worried at first because I didn’t feel unwell and assumed a few drops in my ears would solve the problem.

One ear returned gradually over the day to its full capacity but the other one didn’t.

I went to my Dr’s and explained the situation and was told it was glue ear caused by my ‘slight cold’ and go away and keep pinching my nose and blow through my ears.  He assured me it would clear up eventually.  Well, I had no reason not to believe him so I went away happy in the knowledge that it would come back again.

6 months later after a few more visits to the Dr and being told the same story I pushed to see a specialist.

I had been managing with the one ear as well as possible.  It’s amazing how quickly you adjust to situations……..but more on that later!

I went for CT scans and MRI scans and was told that I had suffered nerve damage and it would never return.

Sounds a bit blunt but that is exactly what I was told.  No explanations, no cures, no help no nothing!!

Well, being only 26 years old and told that I was going to have to survive with one ear was at the time devastating.  I remember walking out of the Specialists office in tears.  I mean……….up to that point I had always assumed that my full hearing would always return.

Well, my life didn’t end there.  Yes life was different.  I couldn’t hear where sounds were coming from.  I had to position myself with everyone to my left (my good ear) in social situations so I could join in the conversations.  (For meals that generally meant sitting at the end of the table………..not so good as I always seemed to be presented with the bill at the end of the night!!). Confused

I became so well practiced in coping that when I met new friends they were always surprised to find out that I only had one good ear.

Fast forward 10 years……………….

April 2009……….We had my Sister and my Niece staying with us and due to lack of space my niece, Victoria, was to sleep on a bed on our bedroom floor.  I had a slight cold so decided to take some decongestant just in case a snored and woke her up.  Well, I woke up the next morning and couldn’t hear anything.  Total panic………….Oh no, what do I do?  Because of my history with my hearing loss before I had always been told to get straight over to A&E and get seen as soon as possible…………….so that’s what I did.  After being seen by assessor and having had great trouble communicating with him he went off to speak to the ENT consultant on duty.  The assessor came back and told me that the ENT consultant didn’t need to see me and that it was just congestion and to go home and wait till it improved!!  I was amazed!!  Even with my history of hearing loss the ENT consultant wouldn’t even see me to tell me themselves.  What ever I said wouldn’t change their mind and so I left feeling, well words couldn’t describe how I felt!!  I went home and got my sister to phone my Dr’s who saw me very quickly.  And you know what they did?  They called ENT and told them about me and I was promptly sent straight over back to were I had just been!!  Amazing!!  4 hrs wasted!!

Luckily, by the time I was seen I could feel my hearing starting to improve.  I had the day at hospital doing hearing tests etc and by the time I got home my hearing had returned to normal.  What a relief!  Maybe I shouldn’t have panicked so much I thought.  Maybe the original consultant was right.  Maybe.

July 2009……….I came down with a virus.  Not sure if it was swine flu but the symptoms matched so had a course of Tamiflu.  This did absolutely nothing.  After about two weeks I eventually started to feel better.  It was a Saturday night and I went to bed as normal.  I woke up with a cough in the middle of the night.  Assuming that was just the last of my virus getting out of me I got up to go downstairs.  (Our house is very noisy and I didn’t want to wake our youngest up, as she still wasn’t sleeping right through the night).  Anyway………as I was going down stairs I realised that I had lost a bit of hearing in my good ear.  Assuming it was a bit of congestion like I had been led to believe back in April 2009 I took a decongestant and went off to sleep on the sofa.  3 hours later I woke up and couldn’t hear anything!!  Now as this had happened earlier in the year to me and it returned over a period of 12 hours or so I didn’t panic.  I spent the day with the family waiting for my hearing to return but by 6pm that evening nothing had improved and I decided to go straight to hospital.

They put me straight on steroids, anti-virals and oxygen and kept me in hospital for a week doing all sorts of hearing tests and blood tests and more blood tests and more blood tests.  According to the Dr’s although I was feeling better from the virus I was still actually quite ill.  My BP was up, my resting heart rate was over 100bpm and my temperature was up around 39.

After a week in hospital it was becoming increasing clear to me that my hearing was not likely to return and I was going to live the rest of my life as a deafened adult.

My family’s life and mine had suddenly been turned upside down in an instant.  I had been given a hearing aid to boost what little hearing I had left but that only allowed me to hear voices close up and I could only understand what was being said if they talked slowly to me and I could see the lips too.

How was I going to cope?

How was my wife going to cope, especially with two young children to cope with?

How will I cope with never being able to hear my children’s voices?

How would it affect my marriage?

How would it affect my social life and friendships?

How was I going to continue my business when my main requirement was good communication skills?

How will I cope at home and work without being able to talk over the phone?

So many questions…………..and at the same time trying to cope with the emotion of actually being totally deaf!

I have no skills usually associated with deafness but I am learning slowly.

My lip reading with the little noise I get from my hearing aid has improved quite quickly and my hearing therapist believes that I have probably been lip reading a bit without knowing to help when I lost the hearing in just one ear.

My favourite programme at the moment is CBB’s Something Special.  Brilliant.  It teaches children and now me and my wife simple signing.  Now we can tell each other if we saw a Tiger or a Giraffe Open-mouthed

It took me a few weeks to come to terms with my deafness and I was getting used to the hearing aid and the noises that it produced when…………..roll on Monday 19th October 2009………I woke up and put my hearing aid in and I couldn’t hear anything other than a buzz when my wife spoke.  Was my hearing aid broken?  It didn’t seem to be.  This time I gave it 2 hrs to improve and promptly went over to hospital AGAIN!  Straight on to the steroids and anti-virals.  I don’t feel unwell and it has become rather tiresome all this dashing around to try and save what little hearing I do have left.

I had another hearing test and it showed another drop in hearing quality!!  As if it could get any worse!!  I have been sent home with a more powerful hearing aid and I am now trying to readjust to my hearing being even worse and more and more relying on lip reading alone.

I feel that this week could be a tough one…………more to follow.

Today is the 21st October 2009 and I am now off for a coffee!!!

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