| |
Abstract:
The purpose of the present study was to determine whether
instructions to categorize primes during a lexical decision task
would result in hemispheric differences in reaction time and
Event-Related Potential (ERP) measures of semantic priming. On each
trial subjects viewed a word (the target) in either the left visual
field (LVF) or the right visual field (RVF), and were asked whether
the target was a real word or a pseudoword. The target was preceded
by a centrally presented word (the prime) that was related,
unrelated, or neutral to the target. Half the subjects were asked
to determine the semantic category of the prime (categorization
condition) while the other half were given neutral instructions
(non-categorization condition). EEG recordings were obtained from
15 scalp locations. The behavioral data indicated a priming effect,
a RVF advantage, and the effectiveness of the categorization
manipulation. An analysis of the P300 component of the ERP at
selected electrodes indicated higher peak amplitudes for the
related condition and for LVF presentations. The magnitude of the
N400 component at the same electrodes was greater for the unrelated
condition and for RVF presentations in the categorization
condition. The larger P300 component for LVF presentations probably
reflects an earlier stage of processing. These findings add ERP
support for visual field differences in facilitation and inhibition
obtained in semantic priming paradigms.
|
