Neuronal interaural level difference response shifts are level-dependent in the rat auditory cortex
Neuronal interaural level difference response shifts are level-dependent in the rat auditory cortex
复制标题
DOI：
10.1152/jn.00648.2013
复制
发表时间：
2014-03-01
影响因子：
2.5
通讯作者：
Wehr, Michael
中科院分区：
文献类型：
--
作者：
Kyweriga, Michael;Stewart, Whitney;Wehr, Michael
大脑是如何在不改变总声级的情况下完成声音定位的？对耳间水平差异（ILD）的敏感性首先在外侧上级橄榄（LSO）计算，并在听觉通路的多个水平观察，包括下丘中央核（ICC）和听觉皮层。在LSO中，这种ILD敏感性是水平依赖性的，使得ILD响应功能随着声音水平的增加而向同侧（兴奋性）耳转移。因此，在处理途径的早期，放电率的变化可能表明声音位置、声音水平或两者的变化。在ICC中，虽然ILD反应可以在单个神经元中向任一耳转移，但在群体水平上没有净ILD反应转移。在人类声音定位敏锐度的行为研究中，ILD灵敏度对增加的声级是不变的。水平不变的声音定位将建议LSO和声源感知之间的水平灵敏度的转换。这一转变是在国际刑事法院一级完成，还是在更高一级继续进行，目前尚不清楚。也不知道感知声音定位是否在大鼠中是水平不变的，就像在人类中一样。我们询问ILD敏感性是否在大鼠听觉皮层中是水平不变的。我们在氯胺酮麻醉下对大鼠听觉皮层进行了单细胞和全细胞记录，并在一系列ILD中测量了对通过密封耳机呈现的白色噪声突发的反应。令人惊讶的是，我们发现随着声音水平的增加，ILD反应向同侧耳（通常是抑制性的）转移，无论细胞是否喜欢同侧，对侧或双耳刺激。电压钳记录表明，突触抑制并没有实质性的贡献，这种转变的水平敏感性。我们的结论是，ILD的敏感性在行为研究中的水平不变性是不存在于大鼠的听觉皮层。
How does the brain accomplish sound localization with invariance to total sound level? Sensitivity to interaural level differences (ILDs) is first computed at the lateral superior olive (LSO) and is observed at multiple levels of the auditory pathway, including the central nucleus of inferior colliculus (ICC) and auditory cortex. In LSO, this ILD sensitivity is level-dependent, such that ILD response functions shift toward the ipsilateral (excitatory) ear with increasing sound level. Thus early in the processing pathway changes in firing rate could indicate changes in sound location, sound level, or both. In ICC, while ILD responses can shift toward either ear in individual neurons, there is no net ILD response shift at the population level. In behavioral studies of human sound localization acuity, ILD sensitivity is invariant to increasing sound levels. Level-invariant sound localization would suggest transformation in level sensitivity between LSO and perception of sound sources. Whether this transformation is completed at the level of the ICC or continued at higher levels remains unclear. It also remains unknown whether perceptual sound localization is level- invariant in rats, as it is in humans. We asked whether ILD sensitivity is level-invariant in rat auditory cortex. We performed single-unit and whole cell recordings in rat auditory cortex under ketamine anesthesia and measured responses to white noise bursts presented through sealed earphones at a range of ILDs. Surprisingly, we found that with increasing sound levels ILD responses shifted toward the ipsilateral ear (which is typically inhibitory), regardless of whether cells preferred ipsilateral, contralateral, or binaural stimuli. Voltage-clamp recordings suggest that synaptic inhibition does not contribute substantially to this transformation in level sensitivity. We conclude that the level invariance of ILD sensitivity seen in behavioral studies is not present in rat auditory cortex.