Lee Hee Yoon, Raphael Patrick D, Park Jesung, Ellerbee Audrey K, Applegate Brian E, Oghalai John S
E. L. Ginzton Laboratory and Department of Electrical Engineering, Stanford University, Stanford, CA 94305; Department of Otolaryngology-Head and Neck Surgery, Stanford University, Stanford, CA 94305; and.
Department of Otolaryngology-Head and Neck Surgery, Stanford University, Stanford, CA 94305; and.
Proc Natl Acad Sci U S A. 2015 Mar 10;112(10):3128-33. doi: 10.1073/pnas.1500038112. Epub 2015 Mar 3.
Sound is encoded within the auditory portion of the inner ear, the cochlea, after propagating down its length as a traveling wave. For over half a century, vibratory measurements to study cochlear traveling waves have been made using invasive approaches such as laser Doppler vibrometry. Although these studies have provided critical information regarding the nonlinear processes within the living cochlea that increase the amplitude of vibration and sharpen frequency tuning, the data have typically been limited to point measurements of basilar membrane vibration. In addition, opening the cochlea may alter its function and affect the findings. Here we describe volumetric optical coherence tomography vibrometry, a technique that overcomes these limitations by providing depth-resolved displacement measurements at 200 kHz inside a 3D volume of tissue with picometer sensitivity. We studied the mouse cochlea by imaging noninvasively through the surrounding bone to measure sound-induced vibrations of the sensory structures in vivo, and report, to our knowledge, the first measures of tectorial membrane vibration within the unopened cochlea. We found that the tectorial membrane sustains traveling wave propagation. Compared with basilar membrane traveling waves, tectorial membrane traveling waves have larger dynamic ranges, sharper frequency tuning, and apically shifted positions of peak vibration. These findings explain discrepancies between previously published basilar membrane vibration and auditory nerve single unit data. Because the tectorial membrane directly overlies the inner hair cell stereociliary bundles, these data provide the most accurate characterization of the stimulus shaping the afferent auditory response available to date.
声音在作为行波沿内耳听觉部分（耳蜗）传播后，在内耳中被编码。半个多世纪以来，一直使用激光多普勒振动测量法等侵入性方法来进行研究耳蜗行波的振动测量。尽管这些研究提供了有关活体内耳蜗内非线性过程的关键信息，这些过程会增加振动幅度并锐化频率调谐，但数据通常仅限于基底膜振动的点测量。此外，打开耳蜗可能会改变其功能并影响研究结果。在此，我们描述了体光学相干断层扫描振动测量法，这是一种通过在具有皮米灵敏度的三维组织体积内以200kHz提供深度分辨位移测量来克服这些限制的技术。我们通过对周围骨骼进行非侵入性成像来研究小鼠耳蜗，以测量体内感觉结构的声音诱发振动，并据我们所知报告了未打开的耳蜗内盖膜振动的首次测量结果。我们发现盖膜维持行波传播。与基底膜行波相比，盖膜行波具有更大的动态范围、更锐的频率调谐以及振动峰值位置的顶端移位。这些发现解释了先前发表的基底膜振动和听神经单单位数据之间的差异。由于盖膜直接覆盖在内毛细胞静纤毛束上，这些数据提供了迄今为止对塑造传入听觉反应的刺激的最准确表征。
