E-ISSN : 2733-4538
The temporal stages of the cognitive processes and the neurophysiological mechanisms underlying the working memory were investigated using the 2-back task and event-related potential (ERP). Geometric figures such as a circle, triangle and square were used as stimuli. The target stimulus was a circle, while the triangle and square served as nontargets. The target stimulus was further divided into the match target and nonmatch target. If the current stimulus was a circle, and the circle was presented two trials earlier (match circle: MC), the subjects were required to respond. If the current stimulus was a circle, but the circle was either not presented two trials earlier (nonmatch circle: NC), or the current stimulus was either a triangle or a square (nontarget stimulus: NS), subjects were asked not to respond. The target stimulus, i. e., MC and NC produced a significantly higher N100 amplitude than the nontarget stimulus, which indicates that more attention was directed to the target stimulus than to the nontarget stimulus. In terms of P300, the MC than either the NC or NS elicited a greater amplitude and earlier latency. In addition, the P300 was at a maximum at the parietal sites in the MC, while it was at its highest at the frontal sites in the NC or NS. All three types of stimuli produced a positive slow potential with similar amplitudes and latencies. The amplitude of the slow potential was at a maximum at the frontal sites. These results indicate that such temporal stages of cognitive functions underlying the working memory as attention allocation, updating the working memory contents and the retention of sequential information can be reflected toward the ERP components. The results also suggest that the prefrontal and parietal cortex, which are known to be the neural networks of working memory, are associated with the retention process and updating working memory contents, respectively.
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