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Abstract:
Previous research has suggested a functional role of the
theta rhythm in various cognitive operations (e.g. Klimesch, Brain
Res. Rev., 1999; Karakas et al., Clin. Neurophysiol., 2000). We
explored the possible role of the theta rhythm during language
processing. In particular, we investigated the sensitivity of theta
to syntactic violations occurring in visually presented sentences.
18 subjects read correct sentences mixed with sentences that
contained either a gender or a number agreement violation.
Event-related theta responses were quantified by computing Induced
Band Power changes (Klimesch et al., Electroenceph. Clin
Neurophysiol., 1998), which extract information from the EEG that
is complementary and non-overlapping with traditional ERP measures.
Regardless of its position in a sentence, each (correct) word
elicited a phasic increase in theta power 300-500 ms after word
onset. Number agreement violations elicited an additional increase
in theta power at left anterior electrodes, whereas gender
agreement violations elicited an additional theta power increase
over right anterior sites. These qualitatively different syntactic
violation effects were specific to the theta frequency range. The
results point to a functional role of the theta rhythm in language
processing. Furthermore, in contrast to traditional ERP results,
they suggest a qualitative difference in the processing of number
and gender agreement violations during sentence processing.
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