Place code for pitch: a necessary revision. 1999

J J Zwislocki, and M Nguyen
Institute for Sensory Research, Syracuse University, NY 13244-5290, USA. joe_zwislocki@isr.syr.edu

It is widely believed that the location of the cochlear excitation maximum, which has been shown by Békésy to depend on sound frequency and move from the cochlear apex to its base as the frequency increases, is a code for subjective pitch. The pitch of a tone is known to be practically independent of sound intensity. If the location does determine the pitch, it too must remain invariant. At the 1990 meeting of the Collegium held in Basel, however, the first author reported compelling indirect evidence indicating that this may not be true. It suggested that, at least in the mid-portion of the cochlea, the most important for speech frequencies, the maximum moves toward the cochlear base as sound intensity is increased. We now have a direct verification of this inference. Recording alternating Hensen's cell potentials at two or three second-turn locations of each of several Mongolian gerbil cochleas, we observed that the maximum response produced by a single tone moved substantially toward the cochlear base as sound intensity increased. For example, an intensity increment of only 10 dB caused the maximum to move by about 0.225 mm. Since Hensen's cells are known to reflect closely the excitation pattern of the outer hair cells, similar to that of the inner hair cells, the discovery makes it impossible for the cochlear excitation maximum to be an adequate code for pitch. We observed, on the other hand, that the apical excitation cut-off did not depend on sound intensity. Every cochlear location investigated had its invariant characteristic cut-off frequency. It is possible, therefore, that the cut-off location provides the place code for pitch. These findings may have profound consequences for our understanding of auditory mechanisms as well as for the technology of cochlear implants.

UI MeSH Term Description Entries
D010897 Pitch Discrimination The ability to differentiate sound frequency or pitch. Discrimination, Pitch,Pitch Discriminations
D003051 Cochlea The part of the inner ear (LABYRINTH) that is concerned with hearing. It forms the anterior part of the labyrinth, as a snail-like structure that is situated almost horizontally anterior to the VESTIBULAR LABYRINTH. Cochleas
D005849 Gerbillinae A subfamily of the Muridae consisting of several genera including Gerbillus, Rhombomys, Tatera, Meriones, and Psammomys. Gerbils,Jird,Meriones,Psammomys,Rats, Sand,Gerbil,Jirds,Merione,Rat, Sand,Sand Rat,Sand Rats
D006198 Hair Cells, Auditory Sensory cells in the organ of Corti, characterized by their apical stereocilia (hair-like projections). The inner and outer hair cells, as defined by their proximity to the core of spongy bone (the modiolus), change morphologically along the COCHLEA. Towards the cochlear apex, the length of hair cell bodies and their apical STEREOCILIA increase, allowing differential responses to various frequencies of sound. Auditory Hair Cells,Cochlear Hair Cells,Auditory Hair Cell,Cell, Cochlear Hair,Cells, Cochlear Hair,Cochlear Hair Cell,Hair Cell, Auditory,Hair Cell, Cochlear,Hair Cells, Cochlear
D000161 Acoustic Stimulation Use of sound to elicit a response in the nervous system. Auditory Stimulation,Stimulation, Acoustic,Stimulation, Auditory
D000818 Animals Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA. Animal,Metazoa,Animalia

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