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Abstract:
Previous studies propose that the processing nature of the
N400 in spatial selective attention and semantic priming reflects
semantic integration. We further explored the effects of spatial
selective attention on semantic categorization. In Experiment 1,
ERPs were recorded from 32 electrode-sites to words presented in
the left and right visual field, while subjects maintained central
eye fixation. Twenty-four subjects responded to words with an
underlined letter "e" in the attended visual field. In Experiment
2, subjects responded to animal names with an underlined letter "e"
in the attended visual field. When no semantic categorization is
required there should be no N400 effect, but a modulation of the
P1-N1 complex in the attended visual field. When semantic
categorization is required, there should be an enhanced P1-N1
complex followed by an N400 in the attended visual field. In
Experiment 1, we found an enhanced P1-N1 complex, but no N400 in
the attended visual field. In Experiment 2, we found a P1-N1 effect
followed by a frontocentral negative-going waveform 500 to 800 msec
poststimulus onset in the attended visual field. Independent of a
P1-N1 attenuation there was a centroparietal negative-going
waveform (500-800 msec) in the unattended visual field. The
processing nature of the N400 is discussed in the context of visual
spatial selective attention.
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