Laboratory of Sensory Neuroscience, The Rockefeller University, New York, New York 10065
Howard Hughes Medical Institute, The Rockefeller University, New York, New York 10065.
J Neurosci. 2024 Oct 30;44(44):e1583242024. doi: 10.1523/JNEUROSCI.1583-24.2024.
The capabilities of the human ear are remarkable. We can normally detect acoustic stimuli down to a threshold sound-pressure level of 0 dB (decibels) at the entrance to the external ear, which elicits eardrum vibrations in the picometer range. From this threshold up to the onset of pain, 120 dB, our ears can encompass sounds that differ in power by a trillionfold. The comprehension of speech and enjoyment of music result from our ability to distinguish between tones that differ in frequency by only 0.2%. All these capabilities vanish upon damage to the ear's receptors, the mechanoreceptive sensory hair cells. Each cochlea, the auditory organ of the inner ear, contains some 16,000 such cells that are frequency-tuned between ∼20 Hz (cycles per second) and 20,000 Hz. Remarkably enough, hair cells do not simply capture sound energy: they can also exhibit an active process whereby sound signals are amplified, tuned, and scaled. This article describes the active process in detail and offers evidence that its striking features emerge from the operation of hair cells on the brink of an oscillatory instability-one example of the critical phenomena that are widespread in physics.
人类耳朵的能力非常出色。通常情况下，我们可以在外部耳朵入口处检测到低至 0 分贝（dB）的声压级阈值的声刺激，这会引起鼓膜振动，其幅度在皮米范围内。从这个阈值到疼痛开始的 120dB，我们的耳朵可以涵盖功率相差万亿倍的声音。我们能够区分频率仅相差 0.2%的音调，这使得我们能够理解言语和享受音乐。所有这些能力都在耳朵的感受器（机械感受器感觉毛细胞）受损时消失。内耳的听觉器官每个耳蜗大约包含 16000 个这样的细胞，它们的频率调谐在 20 Hz（每秒周期）到 20000 Hz 之间。值得注意的是，毛细胞不仅仅是捕捉声音能量：它们还可以表现出一种主动过程，通过这种过程，声音信号被放大、调谐和缩放。本文详细描述了这个主动过程，并提供了证据表明，其显著特征源自于毛细胞在振荡不稳定性边缘的运作——这是物理学中广泛存在的临界现象的一个例子。
