Woldorff M G
Department of Neurosciences, University of California-San Diego, La Jolla.
Psychophysiology. 1993 Jan;30(1):98-119. doi: 10.1111/j.1469-8986.1993.tb03209.x.
In studies of event-related potentials (ERPs), short interstimulus intervals (ISIs) are often employed to investigate certain neural or psychological phenomena. At short ISIs, however, the ERP responses to successive stimuli may overlap, thereby distorting the ERP averages. This paper describes a signal processing approach for analyzing the distortion of ERP averages due to such overlap. In general, the distortion is modeled in terms of mathematical convolutions of the ERP waveform elicited by each type of adjacent stimulus with the corresponding distribution in time of those stimuli relative to the averaging epoch. Using this framework, a number of implications of ERP overlap for experimental design and interpretation are examined, with special emphasis given to selective attention paradigms. It is shown that the possibility of confound due to ERP overlap is widespread in short-ISI experiments, and even the widely used procedure of stimulus randomization does not necessarily control for differential distortion of the ERPs to attended versus unattended stimuli. Problems due to ERP overlap can be particularly serious in short-ISI studies that examine how ERPs (and associated perceptual processes) are influenced by the nature of the preceding stimulus (i.e., stimulus sequence effects). A set of algorithms is presented for estimating and removing the residual distortion due to response overlap from recorded ERP averages. The use of these algorithms, collectively termed the Adjacent Response (Adjar) Technique, can alleviate many of the overlap-related problems that arise when short ISIs are used, thereby enhancing the power of the ERP technique.
在事件相关电位（ERP）研究中，常常采用短刺激间隔（ISI）来探究某些神经或心理现象。然而，在短ISI情况下，对连续刺激的ERP反应可能会重叠，从而扭曲ERP平均值。本文描述了一种信号处理方法，用于分析由于这种重叠导致的ERP平均值的失真。一般来说，这种失真是根据每种相邻刺激引发的ERP波形与这些刺激相对于平均时段在时间上的相应分布的数学卷积来建模的。利用这个框架，研究了ERP重叠对实验设计和解释的一些影响，特别强调了选择性注意范式。结果表明，在短ISI实验中，由于ERP重叠导致混淆的可能性很普遍，甚至广泛使用的刺激随机化程序也不一定能控制ERP对注意刺激与非注意刺激的差异失真。在研究ERP（以及相关的感知过程）如何受到先前刺激性质影响（即刺激序列效应）的短ISI研究中，由于ERP重叠产生的问题可能尤其严重。本文提出了一组算法，用于从记录的ERP平均值中估计和消除由于反应重叠导致的残余失真。使用这些统称为相邻反应（Adjar）技术的算法，可以缓解使用短ISI时出现的许多与重叠相关的问题，从而增强ERP技术的效能。
