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Re: Perception as memory / models of pitch

Dear Martin and list,

Thanks for the reminder.  When you first reported the carbamazepine effect, I was fully prepared to try it myself, but a veterinarian friend talked me out of it! 

1) I'd be grateful if you could clarify my thoughts......  (How) does it necessarily follow that categorization must be coupled as an integral part of this temporal pitch extraction process??  My understanding is that it likely occurs at a different location e.g. language areas (?)

2) Forgive my ignorance, but of all the pitch models in existence, surely at least one (if not all) allows convergence from of the what is extracted from the periodicity with a representation of place (i.e. of the exact cochleotopic location) ?  How can periodicity pitch then be totally separated from pitch height (and therefore cochleotopy) ?  Somebody got a nice neural net I can play with to get a better feel?

3) Another question, how stable must a neural reference (?pacemaker) be to equal the known stability of AP normally (<50 cents) ?  Does such a pacemaker exist for all phase-locking frequencies or even just spanning an octave?

4) Final more remote question.  Has anybody catalogued all the known cases of perception of pseudo-sensory input, which has no basis in peripheral sensors, and which can therefore be categorically determined to be manufactured within the CNS?  e.g. phantom pain, tinnitus....?   Are there key articles devoted to the plausibility (or otherwise) that the CNS likes to keep its signal-to-noise ratio as low as possible thereby eliminating unwanted (unreal) sensory input?

Thanks for any help,



> Date:    Mon, 31 Aug 2009 22:08:47 +0200
> From:    Martin Braun <nombraun@xxxxxxxxx>
> Subject: Re: Perception as memory

> Dear fans of AP shift,

> absolute pitch (AP) does not only shift with age and physiological cycles.
> It also shifts under the influence of medical drugs, such as
> carbamazepine and trimipramine.

> The effect of such drugs on the time constants of membrane dynamics of
> neurons is extensively documented in the literature. From this we can
> conclude that the pitch effects are due to interference with the central
> auditory periodicity analysis that is underlying the perception of pitch.

> The idea that the basilar membrane (BM) in the cochlea might be involved in
> AP shift is disproved by the fact that pitch perception is based on central
> auditory periodicity analysis. The parameters of the BM simply have no
> influence on the periodicity information that the inner ear sends to the
> brain.

> Chaloupka, V., Mitchell, S., Muirhead, R., 1994. Observation of a
> reversible, medication-induced change in pitch perception. J. Acoust.
> Soc. Am. 96, 145-149.

> Koerner, C., Deuschle, M., 2003. Reversible pitch perception shift caused
> by trimipramine (Congress Abstract). Pharmacopsychiatry 36, 241.

> Braun, M., Chaloupka, V., 2005. Carbamazepine induced pitch shift and
> octave space representation. Hear. Res. 210, 85-92.

> Martin

> ---------------------------------------------------------------------
> Martin Braun
> Neuroscience of Music
> S-671 95 Kl=E4ssbol
> Sweden
> web site: http://w1.570.telia.com/~u57011259/index.htm