- Stefan Heim: Research Centre Jülich, Institute of Medicine, AG Brain Mapping, 52425 Jülich, Germany. s.heim@fz-juelich.de
In this functional magnetic resonance imaging (fMRI) study, we investigated the influence of two task (lexical decision, LDT; phonological decision, PDT) on activation in Broca's region (left Brodmann's areas [BA] 44 and 45) during the processing of visually presented words and pseudowords. Reaction times were longer for pseudowords than words in LDT but did not differ in PDT. By combining the fMRI data with cytoarchitectonic anatomical probability maps, we demonstrated that the left BA 44 and BA 45 were stronger activated for pseudowords than for words. Separate analyses for LDT and PDT revealed that the left BA 44 was activated in both tasks, whereas left BA 45 was only involved in LDT. The results are interpreted within a dual-route model of reading with the left BA 44 supporting grapheme-to-phoneme conversion and the left BA 45 being related to explicit lexical search.