virtual channel

C

cammomile

New Member
Joined
Mar 19, 2010
Messages
49
Reaction score
0
Anybody can tell me :

what exactly virtual channel in cochlear implant technologies?

and why did the manufacturer write down their electrode as channel in their brochure, rather than write it as electrode instead?

what's the different between electrode and channel and virtual channel?

and what's the function of each to our hearing?

many thanks!
 
Interesting questions!

The electrode is the device that is actually inserted into one's cochlea.

A channel is a distinct point that can be stimulated by the electrode. Therefore by this definition, an electrode is a series of channels.

A virtual channel is a discrete point that isn't directly stimulated by a channel. By using certain strategies, several channels can stimulate a non-direct point. This makes it appear that there are more channels than actually exist. This way the CI can apply more points to excite on the cochlear nerve to provide better sound perception.

Hope that helps.
 
The device that goes into you cochlear is actually an electrode array.
i.e. a string of independent electrodes - the effect is crudely akin to a piano keyboard in your cochlear with each individual electrode stimulating a particular tone.
Depending on which brand of CI you have the number of electrodes in the array range from 12 to 24..
Each electrode in the array provides a unique "channel" which to your ear will sound like a particular frequency (but It also depends on how the individual electrode is stimulated - pulse rate and things like that).
Thus for a 16 electrode CI system you will presumably have 16 channels.
Channels can be stimulated together (in parallel) giving various effects - much like a chord in music.
However there are complications - stimulating one channel may sound like adjacent channels have been activated (this is called crosstalk) so if we want to activate two adjacent electrodes (channels) it is usually done by sending a pulse to one, then the other but not both at the same time. This is done so fast the user has no idea it is happening.
However, with some clever tinkering it appears that if you stimulate two adjacent electrodes (channels) at the same time in a "special way" it seems that the end nerve stimulation (and therefore tone) appears to be from somewhere between the two electrodes (channels).
So it appears that there is now a new channel between the two provided individually by each of the two adjacent electrodes - this is a "virtual" channel.
An (greatly over-simplified) analogy might be - imagine the colour spectrum ROYGBIV that is 7 colours (Red, Orange, Yellow, Green, Blue, Indigo, Violet).
As you will probably know, the screen on your computer only knows about 3 colours, Red, Green and Blue. However your screen can still show all the colours of the spectrum by simply by activating some of the 3 colours it has in parallel.- so it can display "virtual colour channels" if you like. In fact it can probably display 32000 or more different colours all using the 3 basic colours Red, Green and Blue.
Cochlear implants don't operate anything like that, but as you can imagine, it looks like there is some considerable future in the technology of "CI virtual channels".
 
Back
Top