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弱噪声对小鼠下丘神经元声强敏感性的动态调制

王丹, 皮建辉, 唐佳, 吴飞健, 陈其才

华中师范大学生命科学学院.湖北，武汉 430079；湖南怀化学院生物系.湖南，怀化 418008

摘要

为探讨复杂听环境下行为相关声信号提取的可能机制，研究了弱噪声对下丘（IC）神经元强度－放电率函数（RIF）的影响。实验在9只昆明小鼠（Mus musculus Km）上进行，自由声场刺激条件下，分别记录短纯音刺激以及同步输出短纯音阈下5 dB 包络白噪声刺激时IC神经元的RIF，共获112个IC神经元，测量了其中44个神经元在噪声加入前（w/o）后（w）的RIF。以噪声加入前后RIF的声强动力学范围（DR）、斜率、以及不同声刺激强度的放电率抑制百分比变化为指标，比较分析发现：弱噪声对神经元发放率的影响呈三种类型，即抑制（39/44, 88.6%）、易化（2/44, 4.6%）和无影响（3/44，6.8％），但只有抑制性影响有显著性意义（P < 0.001，n = 39）；弱噪声对阈反应的抑制效应最强，并随纯音强度的增加而逐步减弱（P < 0.0001, n = 39）；此外，弱噪声的抑制作用还使大部分神经元的（31/39，79.5%）DR变窄（P < 0.01，n ＝ 31）、RIF的斜率增加（P < 0.01，n ＝ 31）。上述结果提示，弱噪声参与了下丘神经元声强敏感性的动态调制过程。这一观察为人们深入了解自然听境中声信号提取的中枢机制提供了新认识。

关键词： 弱噪声; 调制; 声强敏感性; 下丘神经元; 小鼠

Dynamic modulations on intensity sensitivity evoked by weak noise in the inferior collicular neurons

Wang Dan, Pi Jianhui, Tang Jia, Wu Feijian, Chen Qicai

School of Life Sciences, Central China Normal University.Wuhan 430079,Hubei；China

Abstract

In order to explore the possible mechanisms by which ethologically relevant sounds can be extracted from complex auditory environments, this study examined the effects of weak noise on the rate-intensity functions (RIFs) of neurons responding to tone burst in the inferior colliculus (IC) of nine mice (Mus musculus Km). Under free field stimuli conditions, a total of 112 IC neurons were recorded. RIFs with and without simultaneously adding a weak noise , of which the intensity was relative to 5 dB below minimum threshold of tone burst, were measured in 44 IC neurons. By means of evaluating the changes of dynamic range (DR), slope of RIFs, and percent inhibition at different tone burst intensities evoked by the weak noise, three types of variations in RIFs were observed, i. e., inhibition (39/44, 88.6%), facilitation (2/44, 4.6%), and no effectiveness (3/44, 6.8%). Statistical analysis indicated that only inhibitory effect of weak noise was significant (P < 0.001, n = 39). The inhibitory effect of weak noise was greater at lower stimulus intensity of tone burst but decreased significantly with increased stimulus intensity (P < 0.0001, n = 39). In addition, the DR and slope of RIFs became narrower and steeper with weak noise presentation, respectively (P < 0.01, n = 31). The results from the present study suggest that weak noise exerts a dynamic modulatory action on acoustical intensity sensitivity of IC neurons, which possibly lead to a better understanding of neural mechanisms underlying the extraction of sound signals from natural auditory scenes.

Key words: Weak noise;modulation;Acoustical intensity sensitivity;Inferior collicular neuron;Mouse

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引用本文：

王丹, 皮建辉, 唐佳, 吴飞健, 陈其才. 弱噪声对小鼠下丘神经元声强敏感性的动态调制[J]. 生理学报 2005; 57 (1): .

Wang Dan, Pi Jianhui, Tang Jia, Wu Feijian, Chen Qicai. Dynamic modulations on intensity sensitivity evoked by weak noise in the inferior collicular neurons. Acta Physiol Sin 2005; 57 (1): (in Chinese with English abstract).