the computational neurophysics of perception

StpNrrs@aol.com wrote:
> robert bristow-johnson wrote:
> 
>>in article 1130629424.117822.102680@f14g2000cwb.googlegroups.com,
>>maestro@ultrapiano.com at StpNrrs@aol.com wrote on 10/29/2005 19:43:
>>
>>
[...]
> 
> "this known neural bottleneck".  Do you mean the disparity in the
> amount of information that the ear sends the brain, at most a few
> thousand haircells firing ten times per second, compared to the
> 44100*16 bits per second required for high-fidelity digital audio
> sound?  The same 'known neural bottleneck' occurs in the eyes - about
> 1000000*3*25 bits per second when your're looking at your computer
> monitor.
> 

Try this. Fill your monitor with approximately 8 point text, and see how
much you can read with your peripheral vision. Not much, eh?

Bryan Hackney wrote:
> StpNrrs@aol.com wrote:
> > robert bristow-johnson wrote:
> >
> >>in article 1130629424.117822.102680@f14g2000cwb.googlegroups.com,
> >>maestro@ultrapiano.com at StpNrrs@aol.com wrote on 10/29/2005 19:43:
> >>
> >>
> [...]
> >
> > "this known neural bottleneck".  Do you mean the disparity in the
> > amount of information that the ear sends the brain, at most a few
> > thousand haircells firing ten times per second, compared to the
> > 44100*16 bits per second required for high-fidelity digital audio
> > sound?  The same 'known neural bottleneck' occurs in the eyes - about
> > 1000000*3*25 bits per second when your're looking at your computer
> > monitor.
> >
>
> Try this. Fill your monitor with approximately 8 point text, and see how
> much you can read with your peripheral vision. Not much, eh?

I was being ironic...

In fact I agree with you, there is obviously hardly any information
going from the eyes and ears into the brain, compared with the number
of bits/sec of digital sound and video.

"robert bristow-johnson" seems to think that the auditory nerves are
rather like internet broadband connections into the inner brain, and
claims that this must cause an information bottleneck.  He proposes the
theory that the ears discard so much information from the original
audio signal that the resultant input into the brain is very lossy and
therefore noisy, and claims that the inner brain is using
noise-reduction techniques on this input to produce the perception of
hi-fi audio.  The idea is basically nonsense, and I pointed out that
the same situation is 1000s of times worse for the optical system, and
therefore unworkable (as you also realise).

It is misleading to think that a sound 'is' the 41000 16-bit samples
per second of digital audio (and that visual information 'is' the
1000000 RGB pixels at 25 frames per second of digital video).  The
sense of sound occurs in the brain - if a tree falls in a forest, it
causes pressure variations in the air but it does not itself make the
sound.

The ears sense variations in air-pressure, and when the brain
recognises features and patterns in that information, it can identify a
sound as similar to something it has heard before.  The vast amount of
understanding of sounds stored in the brain's memory is gained from a
lifetime's experience of hearing, and compensates for the apparently
'low quality signal' that the ears give the brain.

steve sulis wrote:
> FWIW, I recently suffered some inner-ear damage due to a virus ?
> specialists don't definitively know yet. At 1st I was completely deaf
> in the left ear. Gradually the sound is coming back. I now get the
> following properties in my perception of sound :-
> Low freqs(<1000Hz) + High freqs(>3KHz) are ok ( well, as good as they
> ever were)
> Mostly silence from 1KHz -> 2.2KHz, but strong peaks of response at a
> few spot frequencies.

Cochlear implants are sometimes effective in treating cases like yours.
 The damaged area of the ear is connected to the auditory system with
miniature wires, and although the connections are initially random, the
ear learns to make sense of them after a while.  The brain's ability to
compensate for internal damage is remarkable - stroke victims can often
re-learn how to use their limbs if the part of the brain that deals
with them has been damaged.

> The weidest thing is hearing the same pure sinewave a different
> frequencies depending on whether I use the right ear or left ear. The
> difference is like C to F# in the same octave.
> The above figures are not exact, but are roughly what I get.

There are several possible reasons for that, perhaps the rate that the
haircell synapses are firing, or the time it takes for the synapses to
'recharge their batteries', has been affected by the virus and is
different in your damaged ear.

> I had always imagined that perception of frequency would be invarient
> from left to right ear, but now I know better.

The following experiment gives a quite amazing result: take two simple
tunes, the first consisting of ascending notes and the second
consisting of descending notes.  Make two further tunes, each
consisting of alternate notes from the original tunes - these both
sound like a sequence of random ups and downs without any meaningful
'tune' to either of them.  If these two 'non-tunes' are played to the
ears through stereo head-phones, the brain magically sorts them out and
hears the two original melodies, and the listener hears the ascending
tune as coming from one earphone and the descending tune as coming from
the other!  Furthermore, if the stereo head-phones are then reversed
left/right, the listener hears the two melodies in the same ears (left
or right) as before - the brain has learnt to sort out the sound in
that particular way on the first hearing, and interprets what might
otherwise be confusing information the same way on subsequent hearings.


I suppose its something to do with the brain's response to perceiving
two threatening noises simultaneously, one on the left and the other on
the right.  The brain seems to correctly decide where the sounds are
coming from at a higher priority than correctly identifying what the
sounds 'are'.

in article sx69f.38759$5e4.24448@tornado.texas.rr.com, Bryan Hackney at
no@body.home wrote on 10/30/2005 11:29:

> StpNrrs@aol.com wrote:
>> robert bristow-johnson wrote:
>> 
>>> in article 1130629424.117822.102680@f14g2000cwb.googlegroups.com,
>>> maestro@ultrapiano.com at StpNrrs@aol.com wrote on 10/29/2005 19:43:
>>> 
>>> 
> [...]
>> 
>> "this known neural bottleneck".  Do you mean the disparity in the
>> amount of information that the ear sends the brain, at most a few
>> thousand haircells firing ten times per second, compared to the
>> 44100*16 bits per second required for high-fidelity digital audio
>> sound?  The same 'known neural bottleneck' occurs in the eyes - about
>> 1000000*3*25 bits per second when your're looking at your computer
>> monitor.
>> 
> 
> Try this. Fill your monitor with approximately 8 point text, and see how
> much you can read with your peripheral vision. Not much, eh?

listen, man, i'm within 3 months of AARP eligibility.  i'm lucky if i even
read the approximately 8 point text.  i sure as hell can't read street names
in most maps.  i used to be 20/15 but am close to getting reading glasses.

-- 

r b-j                  rbj@audioimagination.com

"Imagination is more important than knowledge."

robert bristow-johnson wrote:

   ...

> listen, man, i'm within 3 months of AARP eligibility.  i'm lucky if i even
> read the approximately 8 point text.  i sure as hell can't read street names
> in most maps.  i used to be 20/15 but am close to getting reading glasses.

Go to it, big boy! I'm 20/30 without my bifocals and 20/15 with them.

Jerry
-- 
Engineering is the art of making what you want from things you can get.
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