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Abstract:
Abstract: A particularly fruitful paradigm for identifying
brain activity related to semantic meaning has been the
presentation of sentences with congruent and incongruent endings
(Kutas, 1997). Positron emission tomography (PET) has indicated a
number of regions are modulated by this paradigm (Mazoyer et al,
1993). These results would benefit from information about
timecourse and relative order of activation. A subsequent study
(Nobre & McCarthy, 1994) found evidence for several
event-related potentials (ERPs) modulated by semantic incongruity
that might correspond to the PET results but source localization
analyses were not reported. In order to build on these findings, a
novel analysis was conducted on an existing dataset with 65
electrode sites, 78 subjects, and 120 sentences. An item average
approach was used (Dien, Frishkoff, Tucker, in press) to produce
120 grand averages corresponding to each sentence. Principal
components analysis was applied to the dataset and parameters such
as word frequency and meaningfulness were correlated over the
sentences with the factors. Source localization analyses of the
data, in conjunction with these parametric analyses, suggest that
an N2 reflects activity in the vicinity of Wernicke's area and an
N3 reflects activity in the vicinity of the middle temporal
region.
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