High sensitivity and selectivity of hearing require an active cochlea. The cochlear sensory epithelium, the organ of Corti, vibrates because of external and internal excitations. The external stimulation is acoustic pressures mediated by the scala fluids, whereas the internal excitation is generated by a type of sensory receptor cells (the outer hair cells) in response to the acoustic vibrations. The outer hair cells are cellular actuators that are responsible for cochlear amplification. The organ of Corti is highly structured for transmitting vibrations originating from acoustic pressure and active outer hair cell force to the inner hair cells that synapse on afferent nerves. Understanding how the organ of Corti vibrates because of acoustic pressure and outer hair cell force is critical for explaining cochlear function. In this study, cochleae were freshly isolated from young gerbils. The organ of Corti in the excised cochlea was subjected to mechanical and electrical stimulation that are analogous to acoustic and cellular stimulation in the natural cochlea. Organ of Corti vibrations, including those of individual outer hair cells, were measured using optical coherence tomography. Respective vibration patterns due to mechanical and electrical stimulation were characterized. Interactions between the two vibration patterns were investigated by applying the two forms of stimulation simultaneously. Our results show that the interactions could be either constructive or destructive, which implies that the outer hair cells can either amplify or reduce vibrations in the organ of Corti. We discuss a potential consequence of the two interaction modes for cochlear frequency tuning.

中文翻译：

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体外 Corti 器官被动和主动振动之间的相互作用

听力的高灵敏度和选择性需要一个活跃的耳蜗。耳蜗感觉上皮，Corti 的器官，由于外部和内部激发而振动。外部刺激是由阶流体介导的声压，而内部刺激是由一种感觉受体细胞（外毛细胞）响应声波振动产生的。外毛细胞是负责耳蜗放大的细胞致动器。Corti 的器官高度结构化，用于将源自声压和活跃的外毛细胞力的振动传递到与传入神经突触的内毛细胞。了解 Corti 器官如何因声压和外毛细胞力而振动对于解释耳蜗功能至关重要。在这项研究中，耳蜗是从年轻的沙鼠中新鲜分离出来的。切除的耳蜗中的 Corti 器官受到类似于天然耳蜗中的声学和细胞刺激的机械和电刺激。使用光学相干断层扫描测量 Corti 振动器官，包括单个外毛细胞的振动器官。表征由于机械和电刺激引起的各个振动模式。通过同时应用两种形式的刺激来研究两种振动模式之间的相互作用。我们的结果表明，这种相互作用可能是建设性的，也可能是破坏性的，这意味着外毛细胞可以放大或减少 Corti 器官中的振动。我们讨论了用于耳蜗频率调谐的两种交互模式的潜在后果。