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Published on: August 18, 2020
Limits on normal cochlear 'third' windows provided by previous investigations of additional sound paths into and out
John J Rosowski1, Peter Bowers1, Hideko H Nakajima1
1Eaton-Peabody Laboratory, Department of Otolaryngology, Massachusetts Eye and Ear, Harvard Medical School, Boston, MA, USA; Speech and Hearing Bioscience and Technology Program, Division of Medical Sciences, Harvard Medical School, Boston, MA, USA.
Abstract:
While most models of cochlear function assume the presence of only two windows into the mammalian cochlea (the oval and round windows), a position that is generally supported by several lines of data, there is evidence for additional sound paths into and out of the inner ear in normal mammals. In this report we review the existing evidence for and against the 'two-window' hypothesis. We then determine how existing data and inner-ear anatomy restrict transmission of sound through these additional sound pathways in cat by utilizing a well-tested model of the cat inner ear, together with anatomical descriptions of the cat cochlear and vestibular aqueducts (potential additional windows to the cochlea). We conclude: (1) The existing data place limits on the size of the cochlear and vestibular aqueducts in cat and are consistent with small volume-velocities through these ducts during ossicular stimulation of the cochlea, (2) the predicted volume velocities produced by aqueducts with diameters half the size of the bony diameters match the functional data within ±10 dB, and (3) these additional volume velocity paths contribute to the inner ear's response to non-acoustic stimulation and conductive pathology.
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