The neural circuitry involved in the reading of German words and pseudowords: A PET study

Silent reading and reading aloud of German words and pseudowords were used in a PET study using (O-15) butanol to examine the neural correlates of rea ding and of the phonological conversion of legal letter strings, with or wi thout meaning. The results of 11 healthy, right-handed volunteers in the ag e range of 25 to 30 years showed activation of the lingual gyri during sile nt reading in comparison with viewing a fixation cross. Comparisons between the reading of words and pseudowords suggest the involvement of the middle temporal gyri in retrieving both the phonological and semantic code for wo rds. The read ng of pseudowords activates the left inferior frontal gyrus, including the ventral part of Broca's area, to a larger extent than the rea ding of words. This suggests that this area might be involved in the sublex ical conversion of orthographic input strings into phonological output code s. (Pre)motor areas were found to be activated during both silent reading a nd reading aloud. On the basis of the obtained activation patterns, it is h ypothesized that the articulation of high-frequency syllables requires the retrieval of their concomitant articulatory gestures from the SMA and that the articulation of low-frequency syllables recruits the left medial premot or cortex.