Reformulated question

[Annemarie Seither-Preisler <preisler@xxxxxxxxxxxxxxx>]

Dear List,

two days ago I put a question on the list that was formulated in quite a
misleading way. Thanks to all who tried to answer it in the way they
understood it. To make the point clear, I want to reformulate it here
again.

I had in mind the study by Steinschneider et al., JASA, 104 (5), 1998,
2935 ff. who found that at the level of the primary auditory cortex
phase locked responses occured only at sites with high best frequencies
up to about 200 Hz (stimuli: alternating polarity click trains), while
spectral information seemed not to be represented at all. On the
contrary, in "low frequency channels" the spectrum of the stimulus was
encoded, but
no phase locking occurred.
The question is, what may be the significance of these results.
Does that mean that the temporal code might not play a role at all in
the low frequency channels or is it more likely that phase locking had
been transformed into a rate-place code before the A1 (perhaps in the
midbrain)? And, if such a transformation had occurred, why did it only
affect the low frequency channels ?
Therefore I wondered if there might be any experiments demonstrating
that a pure place or a pure phase locking code is sufficient to convey
pitch information in the low frequency channels.
I guess while it is easy to demonstrate that phase locking in the high
frequency channels must convey virtual pitch information (AM coding of
unresolved harmonics) it is quite difficult to rule out one mechanism
experimentally in the low frequency region. Amplitude modulated white
noise is ambiguous since it may be coded in both channels.

Do you have any ideas ? What is your opinion ?

Best regards,

Annemarie


--
Dr. Annemarie Seither-Preisler

Department of Experimental Audiology
Biomagnetism Centre
University of Münster
Kardinal von Galen-Ring 10
48129 Münster
Germany
Tel.: ++49 251 83 52543
Fax: ++49 251 83 56882

private: Tel. and Fax: ++49 2573 957927