Matsumoto Atsushi, Iidaka Tetsuya
Division of Cerebral Integration, Department of Cerebral Research, National Institute for Physiological Sciences, Myodaiji, Okazaki, Aichi, Japan.
J Cogn Neurosci. 2008 Nov;20(11):2088-96. doi: 10.1162/jocn.2008.20136.
The formation of an object's cortical representation seems to rely on synchronized neuronal activity within the gamma band frequency range (gamma band activity [GBA]). In this study, we investigated whether electroencephalogram (EEG) GBA, and its phase synchronization between electrodes, is necessary for the formation of nonobject higher-order cognitive representations, using both repetition and homophone priming tasks. In a repetition priming task, the formation of orthographic, phonological, and semantic representations is promoted by a prime word, whereas in the homophone priming task, the formation of only phonological representations is promoted. In the present study, the lexical processing of a target word induced GBA. In the repetition priming task, induced GBA and phase synchronization were decreased by presentation of the prime word (i.e., a repetition suppression effect) within both 200-300 msec and 400-500 msec time windows. In the homophone priming task, the repetition suppression effect was observed only within the 400-500 msec time window. The fact that repetition suppression effects were found in both priming tasks indicates that GBA and phase synchronization are necessary for the formation of phonological and semantic representations of a word. These results also suggest that formation of orthographic and higher-order cognitive representations occurred over different time courses.
物体皮层表征的形成似乎依赖于γ波段频率范围内的同步神经元活动（γ波段活动[GBA]）。在本研究中，我们使用重复启动任务和同音异形词启动任务，研究脑电图（EEG）的GBA及其电极间的相位同步对于非物体高阶认知表征的形成是否必要。在重复启动任务中，启动词促进正字法、语音和语义表征的形成，而在同音异形词启动任务中，仅促进语音表征的形成。在本研究中，目标词的词汇加工诱发了GBA。在重复启动任务中，在200 - 300毫秒和400 - 500毫秒的时间窗口内，启动词的呈现（即重复抑制效应）降低了诱发的GBA和相位同步。在同音异形词启动任务中，仅在400 - 500毫秒的时间窗口内观察到重复抑制效应。在这两种启动任务中均发现重复抑制效应这一事实表明，GBA和相位同步对于单词的语音和语义表征的形成是必要的。这些结果还表明，正字法和高阶认知表征的形成发生在不同的时间进程中。
