The study of the brain mechanism of working memory : event related potential (ERP) analysis on verbal and visuo-spatial stimuli

本研究旨在探讨工作记忆对言语和视空间刺激加工的事件相关电位（ERP）的脑机制。在记忆搜索实验中记录了事件相关电位（ERP）和反应时。在这两个实验中，目标刺激是在刺激集消失后呈现的，并要求受试者决定目标是否在记忆集中（插图）或不在记忆集中（开始）。采用阅读广度测验，测量工作记忆的个体差异。将被试分为高记忆广度组和低记忆广度组，在假名和点刺激条件下，当记忆集合规模较大时，反应时均增加。事件相关电位呈现典型的P300成分。大记忆组P300波幅降低。假名条件下，小记忆集和大记忆集在P300成分上的差异较大。这可能是因为在点条件下进行的是并行加工，而在假名条件下进行的是串行搜索加工。测量了组间假名和点刺激之间的差异以及记忆集合大小的影响。高广度组P300波幅大于低广度组。而且。高广度被试的P300波幅位于额叶，可能是工作记忆的一个部位。

The purpose of this research was to investigate the brain mechanism of working memory on the event related potential (ERP) as to the processing of verbal and visuo-spatial stimuli Event related potential (ERP) and reaction time (RT) were recorded in a memory search experiment, In the verbal experiment, the stimuli were Japanese kana, and the visuo-spatial experiment the stimuli were dots. In the both experiments, the target stimulus was presented after the stimulus set was disappeared, and a subject was requested to decide the target was in the memory set (inset) or was not in the memory set (outset). There were two kinds of memory set size of three (small) and eight (large), and each set sizes, the stimulus presentation duration were 1 and 2 seconds each.Individual differences of working memory were measured with use of reading span test (RST). Subjects were divided into two groups ; high score of RST (high span group) and low score of RST (low span group).The RT increased when the memory set size was large both in the kana and dot stimulus conditions. The ERP showed a typical component of P300. P300 amplitude decreased in the large memory set size condition. The differences between small and large memory set size on P300 components were large in the kana condition. This is probably because a parallel processing was done in dot condition, on the contrary a serial search processing was done in the kana condition.The differences between the kana and dot stimulus and the effect of memory set size were measured between the group. The P300 amplitude was larger in the high span groups as compared with low span groups. Moreover. for high span subjects, P300 amplitude localized in the frontal areas , which is suggested to be a locus of working memory.