Re: Pitch orientation-discriminating feature detectors? (Eckard Blumschein )

Subject: Re: Pitch orientation-discriminating feature detectors?
From:    Eckard Blumschein  <Eckard.Blumschein(at)E-TECHNIK.UNI-MAGDEBURG.DE>
Date:    Wed, 25 Sep 2002 08:01:28 +0200

Dear list, two years ago, Jont and also me obeyed Al's suggestion to purify the list from cochlear and heretical nitty-gritty, respectively. This time, I feel obliged to point you to recent work by Delgutte, see my M240. As far as I understood, it might be an open question whether or not it is really always justified to ascribe perceptual peculiarities like sluggishness, dynamic asymmetry, and masking just to the big unnkown, i.e., the cortex. An apparent bottleneck of hearing is the limited number of inner hair cells. Typically ten auditory nerve fibers contact a single inner hair cell of human. They differ from each other by spontaneous rate and threshold. Just a small percentage of afferents travel to a slightly more basal position and contact OHCs. So the response of auditory nerve to a change of frequency is thought to largely be a Poisson process. It depends on random stepwise neurotransmitter release. The corresponding delay increases towards apex of cochlea. Perhaps, that's why we are able to even distinguish between rarefaction-condensation-rarefaction and condensation-rarefaction-condensation sequences. Goto my M130 and listen to pnp.wav vs. npn.wav. Eckard Frequency peaks (upward-then-downward frequency >modulation) are more salient and produce much lower difference limens >than frequency troughs (downward-then-upward FM). snip> >The next question is of course why would it be useful in the real >world to process differently upward vs. downward frequency >movements...

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