The Place Theory of Pitch Perception

Place Theory

位置理论

High frequency sounds selectively vibrate the basilar membrane of the inner ear near the entrance port (the oval window). Lower frequencies travel further along the membrane before causing appreciable excitation of the membrane. The basic pitch determining mechanism is based on the location along the membrane where the hair cells are stimulated.

高频声音会选择性地振动内耳基底膜靠近入口处（椭圆窗）的区域。低频声音则沿膜更远传播，之后才引起膜的显著激发。确定音调的基本机制是基于毛细胞被刺激的膜上位置。

A schematic view of the place theory unrolls the cochlea and represents the distribution of sensitive hair cells on the organ of Corti. Pressure waves are sent through the fluid of the inner ear by force from the stirrup .

一个简略图展示了地方理论对耳蜗的展开，表示基底膜上毛细胞的分布。通过锤骨施加的力，压力波通过内耳的流体传播。

The place theory is the first step toward an understanding of pitch perception. But considering the extreme pitch sensitivity of the human ear, it is thought that there must be some additional "sharpening" mechanism to enhance the pitch resolution.

位置理论是理解音调感知的第一步。但考虑到人耳对音调的极端灵敏度，人们认为必须存在某种额外的‘锐化’机制来提高音调分辨能力。

Sharpening of Pitch Perception

音调感知的清晰度

The high pitch resolution of the ear suggests that only about a dozen hair cells, or about three tiers from the four banks of cells are associated with each distinguishable pitch. It is hard to conceive of a mechanical resonance of the basilar membrane that sharp. So we look for enhancements of the basic place theory of pitch perception.

耳朵对高音调的分辨能力表明，每个可区分的音调可能只涉及大约十二个毛细胞，或者在四个细胞银行中大约三层。很难想象基底膜有如此尖锐的机械共振。因此，我们寻找对基本位置理论的音调感知的改进。

There must be some mechanism which sharpens the response curve of the organ of Corti, as suggested schematically in the diagram. Several such mechanisms have been suggested.

必须存在某种机制，能够使耳石器官的响应曲线变陡，如图中示意的那样。已提出几种这样的机制。

Mechanisms for Sharpening

锐化机制

Since it seems unlikely that the basic place theory for pitch perception can explain the extraordinary pitch resolution of the human ear, some sharpening mechanism must be operating. Several of the proposed mechanism have the nature of lateral inhibition on the basilar membrane. One way to sharpen the pitch perception would be bring the peak of the excitation pattern on the basilar membrane into greater relief by inhibiting the firing of those hair cells which are adjacent to the peak. Since nerve cells obey an "all-or-none" law, discharging when receiving the appropriate stimulus and then drawing energy from the metabolism to recharge before firing again, one form the lateral inhibition could take is the inhibition of the recharging process since the cells at the peak of the response will be drawing energy from the surrounding fluid most rapidly. Inhibition of the lateral hair cells could also occur at the ganglia, with some kind of inhibitory gating which lets through only those pulses from the cells which are firing most rapidly. It is known that there are feedback signals from the brain to the hair cells, so the inhibition could occur by that means.

由于基本的位置理论似乎无法解释人类耳朵非凡的音调分辨能力，因此必须存在某种增强机制。一些提出的机制具有对基底膜的侧抑制性质。一种增强音调感知的方法可能是通过抑制那些邻近峰值的毛细胞的放电，使基底膜上的激发模式峰值更加突出。由于神经元遵循‘全或无’定律，当接收到适当刺激时放电，然后从代谢中获取能量进行充电以便再次放电，侧抑制的一种形式可能是抑制充电过程，因为响应峰值处的细胞会最迅速地从周围流体中获取能量。侧抑制也可能发生在耳石体，通过某种抑制性门控机制，只允许最快速放电细胞的脉冲通过。已知大脑会向毛细胞发送反馈信号，因此抑制也可以通过这种方式实现。