Mechanical bases of frequency tuning and neural excitation at the base of the cochlea: Comparison of basilar-membrane vibrations and auditory-nerve-fiber responses in chinchilla
Mechanical bases of frequency tuning and neural excitation at the base of the cochlea: Comparison of basilar-membrane vibrations and auditory-nerve-fiber responses in chinchilla
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DOI：
10.1073/pnas.97.22.11744
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发表时间：
2000-10-24
影响因子：
11.1
通讯作者：
Recio, A
中科院分区：
文献类型：
--
作者：
Ruggero, MA;Narayan, SS;Recio, A
我们回顾：的机械起源的耳蜗神经兴奋，侧重于比较的幅度和相位的基底膜（BM）的振动和耳蜗神经纤维的反应，以音调在一个基础网站的灰鼠耳蜗的特征频率接近9千赫位于3.5毫米的卵圆窗。在这个位置，具有高自发活动的纤维的特征频率阈值对应于BM位移或速度的量级为1 nm或50 μ m/s。在很宽的刺激频率范围内，神经阈值不仅由BM位移决定，而是由位移和速度的函数决定。对低频音调的近阈值神经反应与朝向鼓阶的峰值BM速度同步，但在80-90 dB声压级（相对于20微帕斯卡的分贝）和100-110 dB声压级下，反应经历两个接近180度的大相移。这些剧烈的相位变化在BM振动中没有对应物。因此，虽然在阈值水平的编码BM振动到尖峰列车似乎只涉及相对较小的信号转换，极性的神经反应不符合传统的看法BM振动是如何传递到内毛细胞。在阈值水平的响应极性，以及强度依赖性的相位变化，显然反映Corti器官，盖膜和subtectorial流体，和/或电和突触过程的内毛细胞之间的微机械相互作用。
We review: the mechanical origin of auditory-nerve excitation, focusing on comparisons of the magnitudes and phases of basilar-membrane (BM) vibrations and auditory-nerve fiber responses to tones at a basal site of the chinchilla cochlea with characteristic frequency approximate to 9 kHz located 3.5 mm from the oval window. At this location, characteristic frequency thresholds of fibers with high spontaneous activity correspond to magnitudes of BM displacement or velocity in the order of 1 nm or 50 mum/s. Over a wide range of stimulus frequencies, neural thresholds are not determined solely by BM displacement but rather by a function of both displacement and velocity. Near-threshold, auditory-nerve responses to low-frequency tones are synchronous with peak BM velocity toward scala tympani but at 80-90 dB sound pressure level (in decibels relative to 20 microPascals) and at 100-110 dB sound pressure level responses undergo two large phase shifts approaching 180 degrees. These drastic phase changes have no counterparts in BM vibrations. Thus, although at threshold levels the encoding of BM vibrations into spike trains appears to involve only relatively minor signal transformations, the polarity of auditory-nerve responses does not conform with traditional views of how BM vibrations are transmitted to the inner hair cells. The response polarity at threshold levels; as well as the intensity-dependent phase changes, apparently reflect micromechanical interactions between the organ of Corti, the tectorial membrane and the subtectorial fluid, and/or electrical and synaptic processes at the inner hair cells.