The
Effects of Task Relevancy on Event-Related Brain Potentials Elicited
by Infrequently Presented Nonwords and Semantically Deviant words
J. Katayama, Y. Miyata & A. Yagi |
The
study examined the effects of task relevancy upon visual ERPs elicited
by occasionally presented (15% for each) nonwords (NW) and semantically
deviant (SD) words, which were embedded among frequent (70%) words
belonging to the same semantic category (C). Twelve students performed
four tasks; detection of NW, detection of SD, detection of both NW
and SD, and word/nonword-choice. The effect of task relevancy on
the N400 to nonwords was only being overlapped by the parietal P3.
In contrast, the N400 to SD words enlarged and was followed by the
P3 when they became targets. Nonwords elicited larger N400 than SD
words when both of them were not targets. Both rare stimuli elicited
similar N400 when they became targets, and it was also the case when
subjects responded to both NW and SD words in one task. Since the
ERPs in the word/nonword-choice task were similar to those in the
nonword-detection, the effects were not caused by a motor response
itself. DESCRIPTORS: Event-related potentials, N400, Task relevancy,
Semantic categorization.
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