Re: Is there considerable phase locking up to 6 kHz? (jan schnupp )

Subject: Re: Is there considerable phase locking up to 6 kHz?
From:    jan schnupp  <jan.schnupp(at)PHYSIOL.OX.AC.UK>
Date:    Wed, 17 Mar 2004 10:40:34 +0000

Richard F. Lyon wrote:

> Now that I've read Eckard Blumschein's note about how maybe "Pitch
> apparently relates to a kind of autocorrelation that is not based on
> phase locking," I think I need to clarify Jan Schnupp's answer in
> relation to Hi Cheng-Gia's question.
>
> It is fair to say that "most auditory physiologists would be very
> surprised if any mammal was found to phase lock appreciably to
> frequencies above 4 kHz."  But this should NOT be interpreted to mean
> that auditory neurons with a CF above 4 kHz will not show accurate
> synchrony to high-frequency complexes with a lower pitch.  No phase
> locking to frequencies above 4 kHz should be re-phrased as no phase
> locking to sine waves above 4 kHz.
>
Richard is of course absolutely correct about this. If you were to play,
say, an 8kHz carrier tone that was amplitude modulated at 100 Hz then
you would get the 8kHz CF fibres in the auditroy nerve happily phase
locking to the 100 Hz modulator. I'm not sure whether that helps us with
Cheng-Gia's original problem though, as, if I remember correctly, all
three of his tone complexes should have 400 Hz beat frequencies, and
while these beat frequencies should be encoded through temporal (phase
locking) features, the fundamental beat frequency should stay the same.

Jan