Subject: Re: Discussion about "place pitch" concept From: Tony Miller <ajmiller(at)MIT.EDU> Date: Fri, 19 Mar 2004 01:11:41 -0500List members- The following is an excerpt from a commentary by Shihab Shamma in last month's PNAS dealing with the ongoing 'passionate debates between the proponents of two very different theories of pitch': "In recent decades, physiological investigations in humans and animals have attempted to locate and understand the biological substrate underlying pitch perception at various levels of the auditory nervous system. However, despite all efforts, a deep understanding of the mechanisms that give rise to the pitch percept remains elusive. This uncertainty has generated passionate debates between the proponents of two very different theories of pitch, one based on the place or location of neural activation patterns, and the other on their temporal modulations. This state of affairs is now likely to change dramatically in favor of the place theories with the publication of results of intricately designed psychoacoustic experiments by Oxenham et al. (1) reported in this issue of PNAS. " ------------------------------------------------------------------ The article in question (a must read!): ------------------------------------------------------------------ Correct tonotopic representation is necessary for complex pitch perception. Oxenham AJ, Bernstein JG, Penagos H. Proc Natl Acad Sci U S A. 2004 Feb 3;101(5):1421-5. The ability to extract a pitch from complex harmonic sounds, such as human speech, animal vocalizations, and musical instruments, is a fundamental attribute of hearing. Some theories of pitch rely on the frequency-to-place mapping, or tonotopy, in the inner ear (cochlea), but most current models are based solely on the relative timing of spikes in the auditory nerve. So far, it has proved to be difficult to distinguish between these two possible representations, primarily because temporal and place information usually covary in the cochlea. In this study, "transposed stimuli" were used to dissociate temporal from place information. By presenting the temporal information of low-frequency sinusoids to locations in the cochlea tuned to high frequencies, we found that human subjects displayed poor pitch perception for single tones. More importantly, none of the subjects was able to extract the fundamental frequency from multiple low-frequency harmonics presented to high-frequency regions of the cochlea. The experiments demonstrate that tonotopic representation is crucial to complex pitch perception and provide a new tool in the search for the neural basis of pitch. http://www.pnas.org/cgi/content/abstract/101/5/1421 -- Tony Miller Eaton-Peabody Laboratory, Massachusetts Eye and Ear Infirmary 243 Charles St, Boston, MA 02114 ajmiller(at)mit.edu | (617) 510-3629 | http://tonymiller.info