Subject: Re: Effect of duration on pitch perception From: Erik Larsen <elarsen(at)MIT.EDU> Date: Fri, 26 Aug 2005 10:21:13 -0400Martin, I don't agree with your reasoning. You say that the pitch of a complex tone with F0 100 Hz is perceived faster than the pitch of a pure tone with F0 100 Hz, and explain it by a smaller cochlear latency for the higher harmonics of the complex tone. Then you go on to say that this disproves place and pattern theories of pitch, because these would imply slower pitch perception for complex tone vs pure tones, due to additional processing. First: Place/pattern mechanisms of pitch coding are not necessarily more complex than temporal mechanisms, in fact, I would say they may be simpler. 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. Second: According to your argument about latencies, the pitch of a pure tone of F0 500 Hz should be perceived earlier than the pitch of a complex tone of F0 100 Hz with 4 harmonics (including F0). Is there any evidence for this? I would expect the contrary (see my third point below). Also, there should be a rather large difference in the latency of pitch perception between pure tones of F0 100 Hz vs 1 kHz, due to the difference in traveling wave delay. Is there any evidence for this? Third: A (more?) probable reason for the stated difference in latency of pitch perception between complex tones and pure tones is due to the fact that a complex tone provides much more pitch information than a pure tone (because of the additional harmonics). Whether pitch coding is based on a place/pattern or temporal representation, it is a fairly simple matter to go through the math (which we won't do here) and show that the estimate of F0, from a noisy peripheral representation of harmonic frequencies, increases in accuracy as the number of harmonics increases. Because we can also assume internal noise (in the neural processing), the time window that is required to estimate F0 to within that internal noise limit, from the noisy peripheral representation, will be lower for a complex tone than a pure tone. My conclusion is that a latency difference between pitch perception of pure tones vs complex tones probably says nothing about the mechanism of pitch coding, and the effect of traveling wave delays is probably small. Erik -- Erik Larsen Speech and Hearing Bioscience and Technology Harvard-MIT Division of Health Sciences and Technology Cambridge MA > There is a big difference between pure and complex tones, here. Pitch of > the > latter is discriminated much faster. For example, a pitch of a complex tone > with a fundamental f0 = 100 Hz is perceived more than four times as fast as > the pitch of a pure-tone of 100 Hz (Patterson et al., 1983). The probable > reason is that cochlear and neural latencies decrease with frequency, which > means that harmonics provide earlier periodicity information for the pitch > detector than the fundamental. > > [By the way, these results should have been the ultimate death for all > place > and pattern theories of pitch, because these theories necessarily imply > that > f0 pitch should be discriminated slower than pure-tone pitch, due to the > additional neural processing. Well, it's just one of the many examples in > hearing research, where progress has been impeded for decades by massive > self-amputation.] > > Patterson, R.D., Peters, R.W., Milroy, R., 1983. Threshold duration for > melodic pitch. In: R. Klinke, W. Hartmann (Eds.), Hearing - Physiological > bases and Psychophysics, Springer-Verlag, Berlin, pp. 321-25. > > Martin > > ---------------------------- > > Martin Braun > Neuroscience of Music > S-671 95 Klässbol > Sweden > web site: http://w1.570.telia.com/~u57011259/index.htm >