Mechanisms of hearing question
gjohnson at rlc.net
Wed Dec 16 10:08:06 EST 1998
"Didier A. Depireux" wrote:
> First, I apologize for saying "The 7 green books"... 7 was the original
> plan, but by now they are at volume 11... Anyway, these books, in the
> Springer Handbook of Auditory Research series, are the state of the art in
> hearing (and of course many are already outdated!).
> F. Frank LeFever (flefever at ix.netcom.com) wrote:
> : find the time to look systematically at the distinctionns between
> : retina and cochlea that Didier describes, but a nagging question about
> Now, there are differences between the cochlea and the retina, but they may
> not be relevant. As a matter of fact, you can go a long way thinking of the
> cochlea as a one-dimensional retina that looks at the time-windowed Fourier
> transform of the acoustic waveform along a log-frequency axis. That's the
> point of view of our lab, doing recordings in inferior colliculus and
> auditory cortex. I.e., the idea is that once you have gone beyond the
> sensory epithelium, hearing and vision use similar principles to decompose
> and analyze perception (for instance, we use auditory gratings to study
> single units in auditory cortex). The big difference btw cochlea and retina
> is the local iris provided by the outer hair cells, and the timescales
> involved (auditory nerve fibers lock to a stimulus up to 2 kHz, and have
> steady firing rates of up to 200 Hz).
> : to the idea that neural noise enhances detection of extremely
> : weak signals: is this relevant to the point Dider makes about cats
> : detecting signals below the level of Brownian movement? Would this
> : make a sufficiently "non-passive" cochlea?
> I can only say this with certainty: stochastic firing enhancing signal
> detection has only been shown in batracians, where you have the advantage
> that you can change the noise level (by changing the temperature of the
> animal, therefor changing the thermal noise) and therefore study
> transmission as a function of the noise. I don't think (but I don't know
> for sure) that it's been shown in mammals. It could be used.
> However, the point about the OHC is that if you measure the pressure in the
> cochlea at a given frequency (at rest, with no stimulation), you find a
> gaussian type of noise. Nothing exciting there. But once in a while, we
> (mammals) all have these high pitch sounds in one ear, that last about 10
> seconds to a minutes, and that sound like a TV is being turned on. These
> otoacoustic emissions occur all the time, and we don't hear most of them.
> But if you record the pressure at the frequency of one otoacoustic
> emission, you will find a U-shaped distribution of the amplitudes, just as
> you would get from a sinusoidal oscillation. We know that these emissions
> are from the OHC... Draw your conclusions!
The subject emissions may be an active reference signal for an
system for spatial location. Haven't been able to find out much about it, but
Sound, an ultra-high fidelity 3-D sound imaging and recording technique,
includes a pair of reference signals at the ear locations on a human head model
used in recording.
Vestigial Bat Men, perhaps. The nervous system is certainly piggy-backed.
citations. The Holophonic secrets seem to be closely guarded, so maybe not
much is in the
More information about the Neur-sci