Visual word recognition differs in silent reading and verb generation tasks: An MEG study
Previous studies showed that the brain response to a written word depends on whether the word is a target of a lexico-semantic task or is only read. Here we aimed to examine whether the task that uses the presented word not as the target but a cue to produce another word still modifies its recognition process. Using MEG and magnetic source imaging, we compared the spatio-temporal pattern of the brain responses elicited by a noun cue when it was read silently, either without an additional task (SR) or with a requirement to produce an associated verb (VG). We found that the task demands penetrated into early (200 - 300 ms) and late (500 - 800 ms) stages of written word processing by enhancing the brain response under the VG versus SR condition. The cortical sources of the early differential response were localized to the bilateral inferior occipito-temporal and anterior temporal cortices, suggesting elaborate orthographic and lexico-semantic analysis in the VG task. A late effect was observed in the middle and superior temporal gyri and the motor representation of articulators bilaterally and can be associated with enhanced sensorimotor transformations under the VG condition. Overall, our results suggest that written word processing depends on the task goal while intensified linguistic processing recruits bilaterally lateralized networks.