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Abstract:
Abstract: Recent neurolinguistic studies have identified at
least two responses in the temporal region to visually presented
words: one at ~210-280 ms and another at ~300-400 ms following
stimulus-presentation (Kuriki et al 1996, Salmelin et al. 1996,
McGinnis et al 1997). We investigated the effects of repetition
priming in a lexical decision task. Behavioral studies show that
repetition decreases RT. In this study normal subjects made lexical
decision on the second member of pairs of letter strings while
neuromagnetic fields were recorded using a 64-channel SQUID axial
gradiometer. The behavioral results were replicated: RT was
approximately 100 ms faster in the repeated than in the nonrepeated
condition (p<0.05). From the MEG measurements we identified
two responses which appear to be temporal (source localization will
be reported in SF) and conform to previous results: an early
response in the 220-290 ms range and a later one in the 330-400 ms
range. In 6 out of 7 subjects, priming effects were found in the
later but not in the earlier response. The 350 ms range response
occurred approximately 40 ms earlier in the repeated than in the
nonrepeated condition (p<0.05). There was also a correlation
between the latency of the ~350 ms response and reaction times to
words (R2=.51, p<0.01) while no such correlation was found for
the nonwords. Hence the present study provides evidence that the
~350 ms response reflects lexical access.
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