Charting the functional relevance of Broca's area for visual word recognition and picture naming in Dutch using fMRI-guided TMS

Magnetoencephalography (MEG) has shown pseudohomophone priming effects at Broca’s area (specifically pars opercularis of left inferior frontal gyrus and precentral gyrus; LIFGpo/PCG) within ∼100 ms of viewing a word. This is consistent with Broca’s area involvement in fast phonological access during visual word recognition. Here we used online transcranial magnetic stimulation (TMS) to investigate whether LIFGpo/PCG is necessary for (not just correlated with) visual word recognition by ∼100 ms. Pulses were delivered to individually fMRI-defined LIFGpo/PCG in Dutch speakers 75–500 ms after stimulus onset during reading and picture naming. Reading and picture naming reactions times were significantly slower following pulses at 225–300 ms. Contrary to predictions, there was no disruption to reading for pulses before 225 ms. This does not provide evidence in favour of a functional role for LIFGpo/PCG in reading before 225 ms in this case, but does extend previous findings in picture stimuli to written Dutch words.