Subject: From: Robert Withnell <rwithnel(at)INDIANA.EDU> Date: Thu, 1 Apr 2004 12:06:06 -0500Andrew Bell continues to question the exiting notion that energy propagation in the cochlea involves an inertially-mediated fluid flow coupled in to the basilar membrane as a traveling wave. He cites a recent paper by Tianying Ren in Nature Neuroscience as evidence that the reverse propagation of energy does not involve such a traveling wave. As observed by David Mountain, the experimental design of Ren does not exclude a reverse traveling wave. For measurement on the basilar membrane to elucidate a reverse traveling wave requires that the reverse traveling wave be larger in magnitude than any forward traveling wave at the same frequency. This is most likely at a point basal to f2 - at a stimulus frequency ratio that results in a 2f1-f2 DP generated from the nonlinear interaction of f1 and f2 that is larger in the reverse than the forward direction. Comments by Martin Braun: >He did address the reverse traveling wave issue, and he found there is none. >He simultaneous measured stapes vibration and found that, for DPs, it >preceded that of BM vibration. It is possible that Ren's phase-gradient data for stapes vibration involves a wrapping error. Regardless of whether the reverse propagation of energy involves a reverse traveling wave or a compressional wave, there is the little issue of causality if the stapes vibration precedes the generation of the source energy. Robert Withnell