Further studies on the peripheral auditory system of 'CF-FM' bats specialized for fine frequency analysis of Doppler-shifted echoes.
Further studies on the peripheral auditory system of 'CF-FM' bats specialized for fine frequency analysis of Doppler-shifted echoes.
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发表时间：
1977-08
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通讯作者：
N. Suga;P. Jen
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作者：
N. Suga;P. Jen
在胡子蝙蝠(Pteronotus Parnellii Rubiginosus)中，从圆窗记录到的耳蜗微音器(CM)在61 kHz处被敏锐地调谐，并对约61 kHz的音调突发显示出显著的瞬时响应(即其幅度在刺激开始时呈指数增加，在刺激停止时下降)。根据这个暂态响应的时间常数(I-I+0-3ms)和共振频率(6I*I+0-43 kHz)，假定该系统对应于一个二阶滤波器，其Q为204+57。对61 kHz敏感的外周神经元有一个非常尖锐的兴奋区(或调谐曲线)。调谐曲线的Q值随着最佳频率的增加而显著增加，当最佳频率达到61 kHz时，调谐曲线的Q值减小。最佳频率在60-76和61-75千赫之间的单个神经元的Q值为210189。如果CM与基底膜的机械运动直接相关的假设是正确的，那么单个神经元在约61 kHz处非常尖锐的调谐曲线可能仅仅是由于基底膜的机械调谐。由于这种动物主要使用61 khz的声音进行回声定位，而外周听神经元在约61 khz处表现出低阈值和极其尖锐的调谐，它的外周听觉系统专门用于定向声音和回声的主成分的接收和精细频率分析。调谐敏锐的神经元可以对小至o-oi%的频率调制进行编码，因此昆虫的翅膀跳动很容易被它们编码。与共模不同的是，Nx的调谐频率为千赫。最佳频率的这种差异仅仅是由于急剧调谐的谐振器和Nlt的特性，而不是由于可与侧向抑制相比较的机制。
SUMMARY In the mustache bat (Pteronotus parnellii rubiginosus), the cochlear microphonic (CM) recorded from the round window is sharply tuned at 61 kHz and shows a prominent transient response to a tone burst at about 61 kHz (i.e. its amplitude increases exponentially at the onset of the stimulus and decreases at its cessation). In terms of the time constant (I-I + 0-3 ms) and the resonance frequency (6I*I + 0-43 kHz) of this transient response, the Q of this system, assumed to correspond to a second-order filter, is 204 + 57. Peripheral neurones sensitive to 61 kHz have a very sharp excitatory area (or tuning curve). The Q of a tuning curve markedly increases with the rise in best frequency up to 61 kHz and decreases beyond 61 kHz. The Q value of a single neurone with best frequencies between 60-76 and 61-75 kHz is 210189. If the assumption that the CM is directly related to the mechanical motion of the basilar membrane is correct, the very sharp tuning curves of single neurones at about 61 kHz could be simply due to the mechanical tuning of the basilar membrane. Since this animal predominantly uses a 61 kHz sound for echolocation and peripheral auditory neurones show a low threshold and extremely sharp tuning at about 61 kHz, its peripheral auditory system is specialized for the reception and fine-frequency analysis of the principle component of orientation sounds and echoes. Sharply tuned neurones can code a frequency modulation as small as o-oi%, so that the wing beat of an insect would be easily coded by them. Unlike the CM, N x is tuned at 64 kHz. This difference in best frequency is simply due to the properties of a sharply tuned resonator and N lt and not due to a mechanism comparable to lateral inhibition.