🚀 go-pugleaf

On 25 Sep 2006 22:06:45 -0700, "Radium" <glucegen1@excite.com> wrote:

>Hi:
>
>I have read about the neurophone which claims to produce auditory
>perception through nerve stimulation. Something to do with electric
>signals of certain frequencies being sensed as sound by the brain.
>
>Science proves that temporal bone vibration can be used to cause
>auditory pseudohallucinations.
>
>Check out: http://www.priory.com/halluc.htm#pseudo
>
>"Radio-reception. A 35 year old Vietnam combat, veteran (32) started
>to complain of depression, headaches, and hearing blurred voices and
>music. Skull X-rays showed shrapnel metallic densities in the soft
>tissues and cranial bones of the left parieto-occipital region. His
>perception of voices and music were matched with stations in the AM
>broadcast band, and consistently identified the same station in the
>560 Khz range. His radio- reception involved the metal implant diode
>rectification of the radio signal, and its bone transmission to the
>auditory apparatus. Other cases of broadcast reception due to dental
>work have been reported as well."
>
>The above pseudohallucination is no surpise to me and not at all
>fascinating.

>Cochlear implants stimulate the peripheral auditory nerve-endings in
>the cochlea. Electric signals excite these nerve endings. The
>neurophone is said to work differently -- by using electric signals on
>any nerve in the body. At a specific frequency this is supposed to
>stimulate the auditory cortex of the brain. This, according to
>Flantech, causes a perception of sound. Isn't this too good to be true,
>given the state of today's technology?
>
>Links about neurophone:
>
>1. http://www.neurophone.com/home.htm
>
>2. http://www.worldtrans.org/spir/neuro.html
>

Thanks for these links.  This is a fascinating area for
me, since I spent most of my professional career in
hearing research.  But I think the neurophone is
really pseudo-science.  Here's why:

Hearing is a *parallel channel* system.  Each
individual frequency that we can resolve is 
sent from the cochlea on its own individual nerve.
There is a very narrow band of frequencies that
each nerve will respond to at peak sensitivity,
though the band widens out with louder sounds.

Nevertheless, the frequency discrimination is all
done in the cochlea, by electro-mechanical means.
By the time a sound is turned into nerve impulses,
you have to look at the whole array of nerves to
get a picture of the spectrum of the sound. 

A single electrode placed anywhere after the cochlea
can not provide the sensation of frequency, except
in the crudest sense.  You'd only perceive the *envelope*
of the sound, and you'd think that it was at a frequency
corresponding to whatever nerve was stimulated.
(There are several thousand nerves from the cochlea
to handle full range of frequencies we perceive.)

So a gross single electrode is going to sound like
"BUZZbuzzbuzzBUZZbuzBUZZBUZZbuzzbuzz"
That's what patients of the earliest cochlear implants
heard... crude, but a heck of a lot better than nothing.
And it turned out it corresponded well with vowel sounds,
which are hard to pick up from lip-reading, so that a
patient with one of these who could also see the lips
of a speaker could read lips *much* better.  But it was
hopelss for telephone use, for example.

The newer multi-electrode designs can stimulate several
frequency bands at once.  (Even though there are 22
or more electrodes, you get maybe 8 effective ones after
the initial testing.)  Many patients can indeed learn to use
the telephone after practice, but music is pretty lame.

So what's going on with the neurophone?  I am dubious
that it has really helped any patient with cochlear ("nerve") 
deafness, except as a crude lip-reading aid.  There is
simply no way to encode frequency individually to all
of the thousands of nerves... or even to 2 of them!

However, there are some "electrophonic" effects that
have been known as curiosities for about 100 years.
By proper voltage application to tissue, you can actually
make the tissue vibrate, creating regular old acoustic
sound which can then be heard by a normal ear.

I have experimented with this, and it's pretty fiddly.
But anyone who wants to can try this:  Get a good
bench-type osciallator that can drive a 50 ohm load.
(Not sure how important that is, but it worked for me.)
Bend up a paper clip and clamp it under the binding
post of the hot lead of the output, so the wire is 
dangling in the air, sorta springy.  Then set the level
to maybe 10 V or so at frequencies in the 1k-4k
range and *gently* stroke the wire with your fingertip
in a very quiet room. You may or may not want to 
touch the ground post at the same time.  This whole
thing was so unpredictable that I never pursued it
farther (nor, apparently, did anyone else!), but it
*did* produce occasional faint sound, and yes, it
could be heard by skeptical witnesses.

Hope this helps!




Bob Masta
dqatechATdaqartaDOTcom
 
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