Much better explanation of 120 channels.

Here is an amazing posting to the CIHear yahoo forum on this issue:

It takes an understanding of "current steering" technology, which is responsible for the creation of virtual channels, in order to understand how a cochlear implant can produce 120 channels. The unique ICCE electronic architecture of the AB devices dating back to 2001 can do this (so 120 will be immediately backward compatible to folks implanted as far back as 2001 when it comes out!). What's happening is with the simultaneous stimulation but different weighting of adjacent electrodes, the place of neural stimulation is shifted to a point in between the two electrodes. And it constitutes another "channel" because it is focusing the stimulation in a new place on the cochlea in attempt to allow the person to perceive this new place of stimulation as representing a different pitch percept. By varying the weighting of the stimulation on the adjacent electrodes(e.g. 90% on E-10 and 10% on E-11 versus 60% on E-10 and 40% on E-11),the focus of neural stimulation shifts and can create a new pitch percept. By "steering" the current between electrodes in this manner,120 (or more!) channels (or pitch percepts) can be created, all with the stimulation of the same 16 electrodes. Amazing, isn't it! So the strategy doesn;t need to "rove" as you call it, because all the electrodes are stimulated each time. The weighting of the electrode pairs and ultimately where that current is steered, is determined by the characteristics of the incoming sound. So this is potentially a much more precise method of stimulation, providing up to 120 different pitch percepts (if the person's neural survival enables that).

So the concept of 120 being a roving versus fixed strategy is really not an issue here. It's fixed in that all electrodes are stimulated every time, which is a good thing. It's "roving" if you will, because the focus of neural stimulation changes to different places in between the physical electrode contacts. That's different than your device, I know, because since your device does not stim all the electrodes each time, it has to rove up and down picking and choosing which of the 10 or 12 pitches you should hear.

So I wouldn't knock 120 channels if I were you! It's really quite a leap in cochlear implant technology! It's not unrealistic either--I am using it too and can experience the benefits first hand. And because my internal implant enables current steering, I was able to find out through a special software program used in the research studies, that I am able to perceive 284 different pitches! So 120 is a grand leap from 16 or 20, hopefully helping me to make better use of the neural survival I have. I really and truly hope some day you are able to experience something like this.

I have definitely noticed speech in noise improvements--I was at Orogami, a fairly new sushi bar here in Valencia California. All tiled floors and hard wood furniture and walls, tall ceilings--yes, the reverberation was awful! The place was packed, with two tables of 10 surrounding us on both sides where the people were laughing and shouting almost obnoxiously. This was a business dinner and we contemplated going somewhere else where it was quieter so we could readily talk. But I really wanted to try out this restaurant so I made us stay. Low and behold, I was able to carry on a business meeting with my boss in this crazy environment without difficulty! I true CI moment with 120, for sure!

Music at first when I started trying 120 (as part of the in-house clinical trial), sounded not too hot I have to admit. But after two weeks of use, I am hearing instrument combinations that I never knew existed--like the strings playing with the piano and the cymbals playing with the drums. 120 is allowing me to distinguish these for the first time. I mean, I love music with my HiRes programs anyway,but I am now (with 120) just starting to understand some of the many beautiful aspects of music that I have been missing.

It may not happen this way for everyone as we know everyone is unique in what they hear with their CI, but if there is additional potential existing in my auditory system, I sure want to do everything I can to try to make use of it and I really appreciate the fact that AB (and the other companies) don't stop at basic speech understanding in quiet but instead truly want to keep forging ahead to try to allow me to have better and better hearing to not only understand speech, but to enjoy a vast array of listening experiences. thank goodness for research and development!

Sandy
Audiologist and CI user with AB in the BEA