Aertsen A M, Johannesma P I
Biol Cybern. 1981;42(2):145-56. doi: 10.1007/BF00336732.
The spectro-temporal sensitivity of auditory neurons has been investigated experimentally by averaging the spectrograms of stimuli preceding the occurrence of action potentials or neural events ( the APES : Aertsen et al., 1980, 1981). The properties of the stimulus ensemble are contained in this measure of neural selectivity. The spectro-temporal receptive field (STRF) has been proposed as a theoretical concept which should give a stimulus-invariant representation of the second order characteristics of the neuron's system function (Aertsen and Johannesma, 1981). The present paper investigates the relation between the experimental and the theoretical description of the neuron's spectro-temporal sensitivity for sound. The aim is to derive a formally based stimulus-normalization procedure for the results of the experimental averaging procedure. Under particular assumptions, regarding both the neuron and the stimulus ensemble, an integral equation connecting the APES and the STRF is derived. This integral expression enables to calculate the APES from the STRF by taking into account the stimulus spectral composition and the characteristics of the spectrogram analysis. The inverse relation, i.e. starting from the experimental results and by application of a formal normalization procedure arriving at the theoretical STRF, is effectively hindered by the nature of the spectrogram analysis. An approximative "normalization" procedure, based on intuitive manipulation of the integral equation, has been applied to a number of single unit recordings from the grassfrog's auditory midbrain area to tonal and natural stimulus ensembles. The results indicate tha spectrogram analysis, while being a useful real-time tool in investigating the spectro-temporal transfer properties of auditory neurons, shows fundamental shortcomings for a theoretical treatment of the questions of interest.
听觉神经元的频谱 - 时间敏感性已通过对动作电位或神经事件发生之前的刺激频谱图进行平均来进行实验研究（APES：阿尔特森等人，1980年，1981年）。这种神经选择性的测量包含了刺激集合的特性。频谱 - 时间感受野（STRF）已被提出作为一个理论概念，它应该给出神经元系统功能二阶特性的刺激不变表示（阿尔特森和约翰内斯马，1981年）。本文研究了神经元对声音的频谱 - 时间敏感性的实验描述与理论描述之间的关系。目的是为实验平均过程的结果推导一种基于形式的刺激归一化程序。在关于神经元和刺激集合的特定假设下，推导了一个连接APES和STRF的积分方程。这个积分表达式能够通过考虑刺激频谱组成和频谱图分析的特性从STRF计算出APES。相反的关系，即从实验结果出发并通过应用形式归一化程序得到理论STRF，由于频谱图分析的性质而受到有效阻碍。一种基于对积分方程直观操作的近似“归一化”程序已应用于从草蛙听觉中脑区域对音调及自然刺激集合的多个单单元记录。结果表明，频谱图分析虽然是研究听觉神经元频谱 - 时间传递特性的一种有用的实时工具，但在对感兴趣问题的理论处理方面存在根本缺陷。
