Hemispheric asymmetry in lexical decisions: The effects of grammatical class and imageability

It has been suggested that neural systems for lexical processing of nouns a nd verbs are anatomically distinct. The aim of the present study was to inv estigate if brain asymmetry for the processing of these two grammatical cla sses is also different. Neurologically intact adults pel formed a lateraliz ed lexical decision task with grammatically unambiguous words of high, medi um, and low degrees of imagery. For error scores a right visual field (RVF) advantage and an overall effect of imageability were obtained. For latency scores grammatical class and imageability modified visual field difference s: in the noun class a RVF advantage was obtained only for low imagery noun s, while for the verbs the RVF advantage was present for both medium and lo w imagery verbs. These results suggest that the participation of right hemi sphere neural systems in the processing of verbs is more limited than in th e processing of nouns, (C) 1999 Academic Press.