Subject: Re: Effect of duration on pitch perception From: Erik Larsen <elarsen(at)MIT.EDU> Date: Sun, 28 Aug 2005 23:06:50 -0400Hi Martin, I assume you're referring to the Patterson et al paper, which only shows that complex tones evoke a pitch percept faster than pure tones. It doesn't really provide any evidence about mechanisms. Anyway, I don't want to beat this subject to death, but periodicity detection based on place/patterns doesn't need three serial steps. The first step, frequency filtering, obviously already occurs in the cochlea (and its non-negotiable, as I heard someone once say). The only other step that is required afterwards is to have a neuron with excitatory projections from fibers with CFs on the appropriate harmonic grid, and inhibitory projections from fibers with all other CFs. This an artificially simple implementation and there may not be actual evidence for its existence. Nonetheless, I think that pitch detection based on place/pattern vs temporal mechanisms is not necessarily more complex. At least it doesn't *need* to be more complex, or more time-consuming. Best, Erik -- Erik Larsen Speech and Hearing Bioscience and Technology Harvard-MIT Division of Health Sciences and Technology Cambridge MA Martin Braun wrote: > Dear William, Erik, Roy, and others: > > William: > >> One would think that the ear architecture is ideal for parallel >> processing >> in the frequency domain. In that case, one would not expect f0 pitch >> to be >> discriminated more slowly than pure-tone pitch due to the additional >> neural processing. > > > Erik: > >> It doesn't take much processing to detect neural activity at a >> set of harmonically related frequencies. It doesn't matter that more >> neurons activated because the processing can be done in parallel. > > > Of course it would not matter if more neurons were involved. But the point > is that pitch extraction via detection of a spatial pattern could NOT be > done in any kind of parallel processing. It would have to be a SERIAL > processing: > First step: Frequency filtering. > Second step: Storage of the main spectral lines in a neural matrix. > Third step: Detection of a pattern in this matrix that fits a harmonic > reference pattern. > > Not two of these three steps could be done in parallel. > > Periodicity detection in a neural system, however, can easily be done as an > integration of parallel processes. It necessarily has the potential to be > much faster than place-pattern detection. This had been evident already 22 > years ago. > > Martin > > ---------------------------- > > Martin Braun > Neuroscience of Music > S-671 95 Klässbol > Sweden > web site: http://w1.570.telia.com/~u57011259/index.htm >