de Boer Egbert, Shera Christopher A, Nuttall Alfred L
Academic Medical Centre, University of Amsterdam.
Eaton-Peabody Laboratories, Harvard Medical School.
AIP Conf Proc. 2011 Nov;1403(1):557-562. doi: 10.1063/1.3658148.
In many cases a cochlear model suffices to explain (by simulation) the properties of waves in the cochlea. This is not so in the case of a distortion product (DP) set up by presenting two primary tones to the cochlea. A three-dimensional model predicts, apart from a DP wave traveling in the apical direction, a DP wave that travels from the region of overlap of the two tone patterns towards the stapes-setting the stapes in motion so as to produce an otoacoustic emission at the DP frequency. Experimental research has shown, however, that the actual DP wave in the cochlea appears to travel in the opposite direction, from near the stapes to the overlap region. This feature has been termed "inverted direction of wave propagation" (IDWP). The forward wave could result from an unknown process such as a "hidden source" near the stapes. In the present study we have disproved this notion, by using a one-dimensional model of the cochlea. It is found that both reverse and forward waves are set up by the source of nonlinearity, in the same way as has been published in an earlier work. The present results reveal that IDWP in the data corresponds to the region where the DP wave, originally created as a reverse wave but reflected from the stapes, has received so much amplification that it starts to dominate over the reverse wave. Hence we conclude that IDWP in a one-dimensional model is a direct manifestation of cochlear amplification.
在许多情况下，一个耳蜗模型就足以（通过模拟）解释耳蜗中波的特性。但当向耳蜗施加两个基频音而产生畸变产物（DP）时，情况并非如此。一个三维模型预测，除了有一个向顶方向传播的DP波外，还有一个DP波从两个音调模式的重叠区域向镫骨传播，使镫骨运动，从而在DP频率处产生耳声发射。然而，实验研究表明，耳蜗中实际的DP波似乎是朝相反方向传播的，即从镫骨附近传向重叠区域。这一特征被称为“波传播方向反转”（IDWP）。正向波可能源于一个未知过程，比如镫骨附近的“隐藏源”。在本研究中，我们通过使用耳蜗的一维模型否定了这一观点。研究发现，反向波和正向波都是由非线性源产生的，方式与早期一项研究中发表的相同。目前的结果表明，数据中的IDWP对应于这样一个区域，在该区域中，最初作为反向波产生但从镫骨反射的DP波得到了如此多的放大，以至于它开始超过反向波。因此我们得出结论，一维模型中的IDWP是耳蜗放大的直接表现。
