MOROTOMI Takashi Hokkaido University, Faculty of Education, Professor, 教育学部, 教授 (60003951)
KONISHI Kenzo Hyogo College of Medicine, Dept.of Science of Behavior, Assistant Professor, 医学部, 講師 (60068583)
|Budget Amount *help
¥3,400,000 (Direct Cost : ¥3,400,000)
Fiscal Year 2000 : ¥500,000 (Direct Cost : ¥500,000)
Fiscal Year 1999 : ¥500,000 (Direct Cost : ¥500,000)
Fiscal Year 1998 : ¥2,400,000 (Direct Cost : ¥2,400,000)
In a series of experiments using event-related brain potential (ERP) and behavioral measures, we investigated a function of executive or attentional control in working memory, following the theory of Baddeley (1986).
1. A prominent attenuation of N400 due to immediate repetition of words was observed, when both first and second presentations in one ear were the object of attention. However, when participants were required to switch their attention between first and second presentations in the different ears, the repetition effect disappeared. Following the idea that the N400 attenuation occurs because the immediate availability of the decision in working memory forestalls semantic access (Bentin ＆ McCarthy, 1994), the present finding suggests that the attentional switching between ears interferes the use of available decision.
2. In a modified Sternberg memory scanning task, using photos of human faces and objects, and Kanji characters, a large, slow negative wave was observed for task-
relevant probe stimuli. The negativity at the temporo-occipital sites (T5, T6) was sensitive to a memory-set size, whereas fronto-centrally dominant negativity was not. These results, together with recent neuro-imaging findings, suggest that prefrontal activation relates top-down attentional control to govern the task-relevant processing while the fusiform gyrus (and its neighbors) is engaged in maintaining visual information in a highly accessible form over a short period of time (and matching it with an probe input).
3. In a habituation paradigm, the recovery of P200 amplitude was reduced for semantically related test Kanji characters to repetitive Kanji, compared with the unrelated ones, when no task was required. In the semantic matching task, where the participants were required to decide whether or not the repetition and test Kanji characters were semantically related, the priming effect was obtained as the attenuation of the later negative wave N310 (corresponding to N400) for the related test Kanji, instead of P200. The P200 priming effect was interpreted as the semantically related response at the morphological level, which was due to semantic-level activation feeding back to the corresponding morphological-level representation, whereas the N310 effect as a reflection of the semantic-level activation of the semantic associates with the preceding Kanji. The task dependency of semantic priming levels indicated the top-down control in Kanji recognition processes.