de Boer Egbert, Zheng Jiefu, Porsov Edward, Nuttall Alfred L
Academic Medical Center, University of Amsterdam, Room D2-225/226, Meibergdreef 9, 1105 AZ, Amsterdam, The Netherlands.
J Acoust Soc Am. 2008 Mar;123(3):1513-21. doi: 10.1121/1.2828064.
The "classical" view on wave propagation is that propagating waves are possible in both directions along the length of the basilar membrane and that they have identical properties. Results of several recently executed experiments [T. Ren, Nat. Neurosci. 2, 333-334 (2004) and W. X. He, A. L. Nuttall, and T. Ren, Hear. Res., 228, 112-122 (2007)] appear to contradict this view. In the current work measurements were made of the velocity of the guinea-pig basilar membrane (BM). Distortion products (DPs) were produced by presenting two primary tones, with frequencies below the characteristic frequency f(0) of the BM location at which the BM measurements were made, with a constant frequency ratio. In each experiment the phase of the principal DP, with frequency 2f(1)-f(2), was recorded as a function of the DP frequency. The results indicate that the DP wave going from the two-tone interaction region toward the stapes is not everywhere traveling in the reverse direction, but also in the forward direction. The extent of the region in which the forward wave occurs appears larger than is accounted for by classical theory. This property has been termed "inverted direction of wave propagation." The results of this study confirm the wave propagation findings of other authors. The experimental data are compared to theoretical predictions for a classical three-dimensional model of the cochlea that is based on noise-response data of the same animal. Possible physical mechanisms underlying the findings are discussed.
关于波传播的“经典”观点是，沿基底膜长度方向，波可以双向传播且具有相同的特性。最近进行的几项实验（T. Ren，《自然神经科学》2，333 - 334页，2004年；以及W. X. He、A. L. Nuttall和T. Ren，《听觉研究》228，112 - 122页，2007年）的结果似乎与这一观点相矛盾。在当前的工作中，对豚鼠基底膜（BM）的速度进行了测量。通过呈现两个基频，其频率低于进行BM测量的BM位置的特征频率f(0)，并保持恒定的频率比，来产生畸变产物（DPs）。在每个实验中，记录了频率为2f(1)-f(2)的主要DP的相位随DP频率的变化。结果表明，从双音相互作用区域传向镫骨的DP波并非在所有地方都反向传播，也存在正向传播的情况。正向波出现区域的范围似乎比经典理论所解释的要大。这一特性被称为“波传播方向反转”。本研究结果证实了其他作者关于波传播的研究发现。将实验数据与基于同一动物噪声响应数据的耳蜗经典三维模型的理论预测进行了比较。讨论了这些发现背后可能的物理机制。
