Sound-intensity-dependent compensation for the small interaural time difference cue for sound source localization
Sound-intensity-dependent compensation for the small interaural time difference cue for sound source localization
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DOI：
10.1523/jneurosci.4398-07.2008
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发表时间：
2008-07-09
影响因子：
5.3
通讯作者：
Ohmori, Harunori
中科院分区：
文献类型：
--
作者：
Nishino, Eri;Yamada, Rei;Ohmori, Harunori
耳间时差（ITD）是声源定位的重要线索。然而，头部较小的动物经历较小的过渡段，使得过渡段检测困难，特别是对低频声音。在这里，我们描述了一种声强依赖机制，用于补偿3 - 29 d雏鸡层状核（NL）重合检测器神经元中的小ITD信号。通过仿真验证了所假设的补偿机制。体内单单元记录显示，低最佳频率（< 1 kHz）的NL神经元在最差的过渡段时通过抑制放电活动来提高过渡段调谐的对比度，而在最佳过渡段时，放电率随着声强的增加而增加。相比之下，在中高最佳频率（< 1 kHz）的NL神经元中，电平依赖性抑制非常弱，以至于响亮的声音导致最佳和最差过渡段的放电速率增加。在低-最佳频率神经元中，在最坏的ITD处抑制放电活动需要激活上橄榄核（SON），并通过SON的电解损伤消除。频率相关的抑制反映了从SON到NL低频区的密集投影。因此，低频声音中的小过渡段提示部分被SON的声强依赖性抑制所补偿。
Interaural time difference (ITD) is a major cue for sound source localization. However, animals with small heads experience small ITDs, making ITD detection difficult, particularly for low-frequency sound. Here, we describe a sound-intensity-dependent mechanism for compensating for the small ITD cues in the coincidence detector neurons in the nucleus laminaris (NL) of the chicken aged from 3 to 29 d after hatching. The hypothesized compensation mechanisms were confirmed by simulation. In vivo single-unit recordings revealed an improved contrast of ITD tuning in low-best-frequency (< 1 kHz) NL neurons by suppressing the firing activity at the worst ITD, whereas the firing rate was increased with increasing sound intensity at the best ITD. In contrast, level-dependent suppression was so weak in the middle- and high-best-frequency (< 1 kHz) NL neurons that loud sounds led to increases in firing rate at both the best and the worst ITDs. The suppression of firing activity at the worst ITD in the low-best-frequency neurons required the activation of the superior olivary nucleus (SON) and was eliminated by electrolytic lesions of the SON. The frequency-dependent suppression reflected the dense projection from the SON to the low-frequency region of NL. Thus, the small ITD cues available in low-frequency sounds were partly compensated for by a sound-intensity-dependent inhibition from the SON.