Sayles Mark, Winter Ian Michael
Centre for the Neural Basis of Hearing, The Physiological Laboratory, Cambridge, UK.
Brain Res. 2007 Sep 26;1171:52-66. doi: 10.1016/j.brainres.2007.06.098. Epub 2007 Aug 6.
Spike trains were recorded from single units in the ventral cochlear nucleus of the anaesthetised guinea-pig in response to dynamic iterated rippled noise with positive and negative gain. The short-term running waveform autocorrelation functions of these stimuli show peaks at integer multiples of the time-varying delay when the gain is +1, and troughs at odd-integer multiples and peaks at even-integer multiples of the time-varying delay when the gain is -1. In contrast, the short-term autocorrelation of the Hilbert envelope shows peaks at integer multiples of the time-varying delay for both positive and negative gain stimuli. A running short-term all-order interspike interval analysis demonstrates the ability of single units to represent the modulated pitch contour in their short-term interval statistics. For units with low best frequency (approximate < or = 1.1 kHz) the temporal discharge pattern reflected the waveform fine structure regardless of unit classification (Primary-like, Chopper). For higher best frequency units the pattern of response varied according to unit type. Chopper units with best frequency approximate > or = 1.1 kHz responded to envelope modulation; showing no difference between their response to stimuli with positive and negative gain. Primary-like units with best frequencies in the range 1-3 kHz were still able to represent the difference in the temporal fine structure between dynamic rippled noise with positive and negative gain. No unit with a best frequency above 3 kHz showed a response to the temporal fine structure. Chopper units in this high frequency group showed significantly greater representation of envelope modulation relative to primary-like units with the same range of best frequencies. These results show that at the level of the cochlear nucleus there exists sufficient information in the time domain to represent the time-varying pitch associated with dynamic iterated rippled noise.
在麻醉的豚鼠的腹侧耳蜗核中，记录单个神经元的放电序列，以响应具有正增益和负增益的动态迭代波纹噪声。当增益为+1时，这些刺激的短期运行波形自相关函数在时变延迟的整数倍处出现峰值；当增益为-1时，在时变延迟的奇数倍处出现谷值，在偶数倍处出现峰值。相比之下，希尔伯特包络的短期自相关在正增益和负增益刺激下，均在时变延迟的整数倍处出现峰值。运行短期全阶峰峰间隔分析表明，单个神经元能够在其短期间隔统计中表征调制的音高轮廓。对于最佳频率较低（约<或=1.1kHz）的神经元，无论其分类如何（初级样、斩波型），时间放电模式都反映了波形的精细结构。对于最佳频率较高的神经元，反应模式因神经元类型而异。最佳频率约>或=1.1kHz的斩波型神经元对包络调制有反应；对正增益和负增益刺激的反应没有差异。最佳频率在1-3kHz范围内的初级样神经元仍然能够表征具有正增益和负增益的动态波纹噪声之间的时间精细结构差异。没有最佳频率高于3kHz的神经元对时间精细结构有反应。在这个高频组中，斩波型神经元相对于具有相同最佳频率范围的初级样神经元，对包络调制的表征明显更强。这些结果表明，在耳蜗核水平，时域中存在足够的信息来表征与动态迭代波纹噪声相关的时变音高。
