Chang T R, Chiu T W, Sun X, Poon Paul W F
Department of Computer Sciences and Information Engineering, Southern Taiwan University Tainan, Taiwan, ROC.
Chin J Physiol. 2010 Dec 31;53(6):430-8.
Spectro-temporal receptive fields (STRFs) are commonly used to characterize response properties of central auditory neurons and for visualizing 'trigger features'. However, trigger features in STRF maps typically have a blurry appearance. Therefore it is unclear what details could be embedded in them. To investigate this, we developed a new method called 'progressive thresholding' to resolve fine structures in the STRFs, and applied the method to FM responses recorded from single units at the auditory midbrain of anesthetized rats. Random FM tones of a narrow frequency range (approximately 0.5 octave) were first presented to evoked spike responses at the cell's best frequency. Perispike modulating time waveforms collected (50 msec long, n = 1500 to 4000 tracings) were used to generate STRF based on spike-triggered-averaging. After supra-threshold areas of pixel counts had been determined through a step of progressive thresholding in the map, those peri-spike modulating waveforms passing through each area were dejittered systematically. At what seemed to be an optimal threshold, multiple trigger features (up to a maximum of 4 fine bands) were extracted from the initially simple-looking STRF. Results show that fine FM trigger features are present in STRFs and that they can be resolved with the present method of analysis.
频谱-时间感受野（STRF）通常用于表征中枢听觉神经元的反应特性以及可视化“触发特征”。然而，STRF图谱中的触发特征通常外观模糊。因此，尚不清楚其中可能嵌入了哪些细节。为了研究这一问题，我们开发了一种名为“渐进阈值化”的新方法来解析STRF中的精细结构，并将该方法应用于从麻醉大鼠听觉中脑单个神经元记录的调频（FM）反应。首先呈现窄频率范围（约0.5倍频程）的随机FM音调，以在细胞的最佳频率诱发尖峰反应。收集的每个尖峰周围调制时间波形（50毫秒长，n = 1500至4000条轨迹）用于基于尖峰触发平均生成STRF。在通过图谱中的渐进阈值化步骤确定像素计数的超阈值区域后，系统地去除穿过每个区域的那些尖峰周围调制波形的抖动。在看似最佳的阈值下，从最初看似简单的STRF中提取了多个触发特征（最多4个细带）。结果表明，STRF中存在精细的FM触发特征，并且可以用目前的分析方法解析它们。
