Louage Dries H G, van der Heijden Marcel, Joris Philip X
Laboratory of Auditory Neurophysiology, Medical School, K.U.Leuven, B-3000 Leuven, Belgium.
J Neurophysiol. 2004 May;91(5):2051-65. doi: 10.1152/jn.00816.2003.
Temporal information in the responses of auditory neurons to sustained sounds has been studied mostly with periodic stimuli, using measures that are based on Fourier analysis. Less information is available on temporal aspects of responses to nonperiodic wideband sounds. We recorded responses to a reference Gaussian noise and its polarity-inverted version in the auditory nerve of barbiturate-anesthetized cats and used shuffled autocorrelograms (SACs) to quantify spike timing. Two metrics were extracted from the central peak of autocorrelograms: the peak-height and the width at halfheight. Temporal information related to stimulus fine-structure was isolated from that to envelope by subtracting or adding responses to the reference and inverted noise. Peak-height and halfwidth generally behaved as expected from the existing body of data on phase-locking to pure tones and sinusoidally amplitude-modulated tones but showed some surprises as well. Compared with synchronization to low-frequency tones, SACs reveal large differences in temporal behavior between the different classes of nerve fibers (based on spontaneous rate) as well as a strong dependence on characteristic frequency (CF) throughout the phase-locking range. SACs also reveal a larger temporal consistency (i.e., tendency to discharge at the same point in time on repeated presentation of the same stimulus) in the responses to the stochastic noise stimulus than in the responses to periodic tones. Responses at high CFs reflect envelope phase-locking and are consistent with previous reports using sinusoidal AM. We conclude that the combined use of broadband noise and SAC analysis allow a more general characterization of temporal behavior than periodic stimuli and Fourier analysis.
听觉神经元对持续声音反应中的时间信息大多是通过基于傅里叶分析的方法，利用周期性刺激来进行研究的。关于对非周期性宽带声音反应的时间方面的信息则较少。我们记录了巴比妥麻醉猫的听神经对参考高斯噪声及其极性反转版本的反应，并使用混洗自相关图（SAC）来量化脉冲发放时间。从自相关图的中心峰值提取了两个指标：峰值高度和半高宽度。通过减去或加上对参考噪声和反转噪声的反应，将与刺激精细结构相关的时间信息与包络相关的时间信息分离。峰值高度和半宽度的表现通常与现有的关于对纯音和正弦调幅音锁相的数据一致，但也有一些意外之处。与对低频音的同步相比，SAC揭示了不同类别的神经纤维（基于自发放率）在时间行为上的巨大差异，以及在整个锁相范围内对特征频率（CF）的强烈依赖性。SAC还揭示了在对随机噪声刺激的反应中，其时间一致性（即对同一刺激重复呈现时在同一时间点发放的倾向）比在对周期性音调的反应中更大。高CF处的反应反映了包络锁相，并且与之前使用正弦调幅的报告一致。我们得出结论，与周期性刺激和傅里叶分析相比，宽带噪声和SAC分析的结合使用能够对时间行为进行更全面的表征。
