Department of Otorhinolaryngology Head and Neck Surgery, Beijing Chaoyang Hospital, Capital Medical University, Beijing, China.
Department of Neurophysiology, Capital Medical University, Beijing, China.
Neural Regen Res. 2014 Feb 15;9(4):420-9. doi: 10.4103/1673-5374.128250.
The precedence effect is a prerequisite for faithful sound localization in a complex auditory environment, and is a physiological phenomenon in which the auditory system selectively suppresses the directional information from echoes. Here we investigated how neurons in the inferior colliculus respond to the paired sounds that produce precedence-effect illusions, and whether their firing behavior can be modulated through inhibition with gamma-aminobutyric acid (GABA). We recorded extracellularly from 36 neurons in rat inferior colliculus under three conditions: no injection, injection with saline, and injection with gamma-aminobutyric acid. The paired sounds that produced precedence effects were two identical 4-ms noise bursts, which were delivered contralaterally or ipsilaterally to the recording site. The normalized neural responses were measured as a function of different inter-stimulus delays and half-maximal interstimulus delays were acquired. Neuronal responses to the lagging sounds were weak when the inter-stimulus delay was short, but increased gradually as the delay was lengthened. Saline injection produced no changes in neural responses, but after local gamma-aminobutyric acid application, responses to the lagging stimulus were suppressed. Application of gamma-aminobutyric acid affected the normalized response to lagging sounds, independently of whether they or the paired sounds were contralateral or ipsilateral to the recording site. These observations suggest that local inhibition by gamma-aminobutyric acid in the rat inferior colliculus shapes the neural responses to lagging sounds, and modulates the precedence effect.
优先效应是在复杂听觉环境中准确进行声音定位的前提，是听觉系统选择性抑制回声方向信息的生理现象。在这里，我们研究了下丘脑中的神经元对产生优先效应错觉的成对声音的反应，以及它们的放电行为是否可以通过抑制γ-氨基丁酸（GABA）来调节。我们在三种条件下从大鼠下丘脑中记录了 36 个神经元的细胞外活动：无注射、生理盐水注射和γ-氨基丁酸注射。产生优先效应的成对声音是两个相同的 4ms 噪声突发，它们分别从对侧或同侧传送到记录部位。以不同的刺激间延迟为函数来测量归一化的神经反应，并获得半最大刺激间延迟。当刺激间延迟较短时，滞后声音的神经元反应较弱，但随着延迟的延长，反应逐渐增强。生理盐水注射没有改变神经反应，但局部应用γ-氨基丁酸后，滞后刺激的反应被抑制。γ-氨基丁酸的应用影响了滞后声音的归一化反应，而与滞后声音或成对声音是同侧还是对侧无关。这些观察结果表明，大鼠下丘脑中的局部γ-氨基丁酸抑制作用塑造了滞后声音的神经反应，并调节了优先效应。
