Hauk O, Pulvermüller F
Medical Research Council, Cognition and Brain Sciences Unit, 15 Chaucer Road, Cambridge CB2 2EF, UK.
Clin Neurophysiol. 2004 May;115(5):1090-103. doi: 10.1016/j.clinph.2003.12.020.
We investigated the influence of the length and frequency of printed words on the amplitude and peak latencies of event-related potentials (ERPs). This served two goals, namely (I) to clarify their possible effects as confounds in ERP experiments employing word-stimuli, and (II) to determine the point in time of lexical access in visual word recognition.
EEG was recorded from 64 scalp sites while subjects (n=12) performed a lexical decision task. Word length and frequency were orthogonally varied between stimulus groups, whereas variables including regularity of spelling and orthographic tri-gram frequency were kept constant.
Long words produced the strongest brain response early on (approximately 100 ms after stimulus onset), whereas those to short words became strongest later (150-360 ms). Lower ERP amplitudes were elicited by words with high frequency compared with low frequency words in the latency ranges 150-190 ms and 320-360 ms. However, we did not find evidence for a robust alteration of peak latencies with word frequency.
Length and frequency of word stimuli have independent and additive effects on the amplitude of the ERP. Studies on the precise time course of cognitive processes should consider their potentially confounding character. Our data support the view that lexical access takes place as early as 150 ms after onset of written word stimuli.
我们研究了印刷单词的长度和频率对事件相关电位（ERP）的波幅和峰潜伏期的影响。这有两个目的，即（I）在采用单词刺激的ERP实验中，阐明它们作为混淆因素可能产生的影响；（II）确定视觉单词识别中词汇通达的时间点。
在12名受试者执行词汇判断任务时，从64个头皮部位记录脑电图（EEG）。刺激组之间单词长度和频率呈正交变化，而包括拼写规则性和正字法三字母组频率在内的变量保持不变。
长单词在早期（刺激开始后约100毫秒）产生最强的脑反应，而短单词的脑反应在后期（150 - 360毫秒）最强。在150 - 190毫秒和320 - 360毫秒潜伏期范围内，高频单词引发的ERP波幅低于低频单词。然而，我们没有发现峰潜伏期随单词频率发生显著变化的证据。
单词刺激的长度和频率对ERP波幅有独立且累加的影响。关于认知过程精确时间进程的研究应考虑它们潜在的混淆特性。我们的数据支持这样的观点，即词汇通达在书面单词刺激开始后150毫秒就已发生。
