Yin T C
Department of Neurophysiology, University of Wisconsin, Madison 53706.
J Neurosci. 1994 Sep;14(9):5170-86. doi: 10.1523/JNEUROSCI.14-09-05170.1994.
The precedence effect (PE) describes an illusion produced when two similar sounds are delivered in quick succession (interclick delays of 2-8 msec) from sound sources at different locations so that only a single sound is perceived. The localization of the perceived sound is dominated by the location of the leading sound. If the delays are very short (< 1-2 msec), summing localization occurs and a phantom source is perceived whose location is toward the leading sound. The purpose of these experiments was to look for physiological correlates of the precedence effect and summing localization by recording from single neurons in the inferior colliculus of the anesthetized cat. Click stimuli were delivered under two different situations: over headphones in dichotic experiments and through two speakers in an anechoic room in free-field studies. In the latter case the cat was placed midway between the speakers and a single click stimulus was delivered to each speaker with variable interclick delays (ICDs). Most cells, under both dichotic and free-field conditions, exhibited a form of the precedence effect in which the response to the lagging click was suppressed when ICDs were short. The suppression of the lagging click, or echo, was measured by recovery curves, which plotted the response of the lagging click as a function of ICD. There was considerable variability in the recovery curves from different cells: the ICDs at which the recovery reached 50%, which is a measure of the echo threshold for the cell, ranged from 1 to 100 msec with a median of 20 msec. Human psychophysical experiments report echo thresholds for clicks ranging from 2 to 8 msec. If we assume that absolute echo threshold is determined by the cells with shortest recovery curves, then the thresholds for single cells are in accord with the psychophysical results. The possible sites of generation of the echo suppression are also considered. Changes in the relative level of the leading and lagging clicks produced the expected shifts in the recovery curves. With short ICDs in the summing localization range (between about +/- 2 msec) cells also showed responses consonant with the human psychophysical result that the sound source is localized to a phantom image between the two speakers and toward the leading one. The location of the image varied systematically with the relative levels or ICDs of the clicks.(ABSTRACT TRUNCATED AT 250 WORDS)
优先效应（PE）描述了一种错觉，当两个相似的声音从不同位置的声源快速连续发出（点击间隔延迟为2 - 8毫秒）时，人们只能感知到一个声音。所感知声音的定位主要由领先声音的位置决定。如果延迟非常短（< 1 - 2毫秒），则会出现总和定位，并且会感知到一个虚拟声源，其位置朝向领先声音。这些实验的目的是通过记录麻醉猫下丘的单个神经元，寻找优先效应和总和定位的生理相关因素。点击刺激在两种不同情况下呈现：在双耳实验中通过耳机呈现，在自由场研究中通过消声室中的两个扬声器呈现。在后一种情况下，将猫放置在两个扬声器中间，并以可变的点击间隔延迟（ICD）向每个扬声器发送单个点击刺激。在双耳和自由场条件下，大多数细胞都表现出一种优先效应形式，即当ICD短时，对滞后点击的反应会受到抑制。滞后点击或回声的抑制通过恢复曲线来测量，该曲线绘制了滞后点击的反应作为ICD的函数。不同细胞的恢复曲线存在相当大的变异性：恢复达到50%时的ICD（这是细胞回声阈值的一种度量）范围从1到100毫秒，中位数为20毫秒。人类心理物理学实验报告的点击回声阈值范围为2到8毫秒。如果我们假设绝对回声阈值由恢复曲线最短的细胞决定，那么单个细胞的阈值与心理物理学结果一致。还考虑了回声抑制的可能产生部位。领先和滞后点击相对水平的变化导致恢复曲线出现预期的偏移。在总和定位范围内（约±2毫秒之间），当ICD短时，细胞的反应也与人类心理物理学结果一致，即声源定位在两个扬声器之间并朝向领先扬声器的虚拟图像处。图像的位置随点击的相对水平或ICD而系统变化。（摘要截断于250字）
