Division of Neurobiology, University of Munich, and Bernstein Center for Computational Neuroscience Munich, Grosshaderner Strasse 2, 82152 Planegg-Martinsried, Germany.
J Acoust Soc Am. 2010 Feb;127(2):931-942. doi: 10.1121/1.3282997.
Temporal correlations between the sound waves arriving at the two ears are used to extract the azimuthal position of sound sources. Nerve cells in the mammalian medial superior olive (MSO) that extract these binaural correlations are sensitive to interaural time differences (ITDs) in the range of about 10 micros. These neurons receive inputs from the two ears via four pathways, two excitatory and two inhibitory ones. In this paper, a simple linear model is fitted to the frequency dependence of ITD sensitivity of MSO neurons, which is quantified by the two parameters, characteristic phase and characteristic delay. The fit parameters are the relative delays and the relative strengths of the two inhibitory pathways and thus specify the underlying ITD-detecting circuit assuming a non-Jeffress-like situation, i.e., no excitatory delay lines but phase-locked inhibition. The fitting procedure finds the parameters of these inhibitory pathways such that they account for a desired frequency dependence of ITD sensitivity. It is found that positive characteristic delays require a finite amount of ipsilateral inhibition that arrives at roughly the same time as ipsilateral excitation as well as contralateral inhibition that lags contralateral excitation so much that it effectively leads excitation of the next cycle.
到达两耳的声波之间的时间相关性被用于提取声源的方位角位置。从两耳接收输入的哺乳动物中脑上橄榄复合体（MSO）中的神经细胞对大约 10 微秒范围内的耳间时间差（ITD）敏感。这些神经元通过四个途径接收来自两个耳朵的输入，两个兴奋性的和两个抑制性的。在本文中，一个简单的线性模型被拟合到 MSO 神经元的 ITD 敏感性的频率依赖性上，其由两个参数量化，特征相位和特征延迟。拟合参数是两个抑制性途径的相对延迟和相对强度，因此在假设非杰弗里斯式情况（即没有兴奋性延迟线，但相位锁定抑制）下指定了潜在的 ITD 检测电路。拟合过程找到这些抑制性途径的参数，使得它们能够解释 ITD 敏感性的所需频率依赖性。结果发现，正的特征延迟需要一定量的同侧抑制，其到达的时间与同侧兴奋大致相同，以及对侧抑制延迟得如此之多，以至于它有效地导致下一个周期的兴奋。
