Semantic processing of open- and closed-class words: an event-related potentials study

Previous research on open- and closed-class words has revealed the existenc e of several differences in the processing of these types of vocabulary. In this paper the processing of open- and closed-class words was compared by means of an early electrical brain response, recognition potential (RP), wh ich indexes semantic processing and originates from basal extrastriate area s. The effects of word frequency on closed-class words were also investigat ed. For these purposes, open- and dosed-class words, among other stimuli, w ere presented by means of the rapid stream stimulation procedure. Results s howed that there were no significant differences when comparing the RP evok ed by open- and closed-class words in the left hemisphere. However. in the right hemisphere this situation changed: the RP evoked by open- and closed- class words did differ. Moreover, there were no differences between the RP evoked by closed-class words and pseudowords, These patterns of results sug gest that the semantic processing of closed-class words shares some aspects with the processing of open-class words. despite the existence of some dif ferences. Thus, whereas the semantic processing of open-class words recruit s brain areas of both hemispheres, the semantic processing of closed-class words is left-lateralized. A second purpose of this work is to study word-f requency effects on closed-class words. Our results show the insensitivity of closed-class words to word-frequency effects. (C) 2001 Elsevier Science B.V. All rights reserved.