Bergevin Christopher, Manley Geoffrey A, Köppl Christine
Department of Physics & Astronomy and Centre for Vision Research, York University, Toronto, ON, M3J 1P3, Canada; and
Cluster of Excellence "Hearing4all," Research Center Neurosensory Science, and Department of Neuroscience, School of Medicine and Health Sciences, Carl von Ossietzky University, 26129 Oldenburg, Germany.
Proc Natl Acad Sci U S A. 2015 Mar 17;112(11):3362-7. doi: 10.1073/pnas.1418569112. Epub 2015 Mar 3.
Otoacoustic emissions (OAEs) are faint sounds generated by healthy inner ears that provide a window into the study of auditory mechanics. All vertebrate classes exhibit OAEs to varying degrees, yet the biophysical origins are still not well understood. Here, we analyzed both spontaneous (SOAE) and stimulus-frequency (SFOAE) otoacoustic emissions from a bird (barn owl, Tyto alba) and a lizard (green anole, Anolis carolinensis). These species possess highly disparate macromorphologies of the inner ear relative to each other and to mammals, thereby allowing for novel insights into the biomechanical mechanisms underlying OAE generation. All ears exhibited robust OAE activity, and our chief observation was that SFOAE phase accumulation between adjacent SOAE peak frequencies clustered about an integral number of cycles. Being highly similar to published results from human ears, we argue that these data indicate a common underlying generator mechanism of OAEs across all vertebrates, despite the absence of morphological features thought essential to mammalian cochlear mechanics. We suggest that otoacoustic emissions originate from phase coherence in a system of coupled oscillators, which is consistent with the notion of "coherent reflection" but does not explicitly require a mammalian-type traveling wave. Furthermore, comparison between SFOAE delays and auditory nerve fiber responses for the barn owl strengthens the notion that most OAE delay can be attributed to tuning.
耳声发射（OAEs）是由健康内耳产生的微弱声音，为听觉力学研究提供了一个窗口。所有脊椎动物类群都不同程度地表现出耳声发射，但其生物物理起源仍未得到很好的理解。在这里，我们分析了一只鸟类（仓鸮，Tyto alba）和一只蜥蜴（绿安乐蜥，Anolis carolinensis）的自发性耳声发射（SOAE）和刺激频率耳声发射（SFOAE）。相对于彼此以及与哺乳动物相比，这些物种的内耳具有高度不同的宏观形态，从而能够对耳声发射产生的生物力学机制有新的见解。所有耳朵都表现出强大的耳声发射活动，我们的主要观察结果是，相邻SOAE峰值频率之间的SFOAE相位累积聚集在一个整数周期左右。与已发表的人类耳朵研究结果高度相似，我们认为这些数据表明，尽管缺乏被认为对哺乳动物耳蜗力学至关重要的形态特征，但所有脊椎动物的耳声发射都有一个共同的潜在产生机制。我们认为耳声发射起源于耦合振荡器系统中的相位相干，这与“相干反射”的概念一致，但并不明确需要哺乳动物类型的行波。此外，对仓鸮的SFOAE延迟和听神经纤维反应的比较强化了这样一种观点，即大多数耳声发射延迟可归因于调谐。
