Reformulated question (Annemarie Seither-Preisler )

Subject: Reformulated question
From:    Annemarie Seither-Preisler  <preisler(at)UNI-MUENSTER.DE>
Date:    Fri, 20 Oct 2000 00:38:32 +0100

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 M=FCnster Kardinal von Galen-Ring 10 48129 M=FCnster Germany Tel.: ++49 251 83 52543 Fax: ++49 251 83 56882 private: Tel. and Fax: ++49 2573 957927

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