Task demands shape network interactions during reading and visual form processing

Current theories of reading, based largely on lesion studies, propose that left fusiform gyrus (FusG) is a crucial hub linking visual inputs into the perisylvian language system. However, FusG is also involved in visual form processing more generally, raising the question of whether its engagement with language cortex and other relevant brain regions changes according to task demands, and whether this flexibility is linked to reading proficiency. To answer these questions, we exploit a large, pre-existing, reading-based language fMRI dataset, in which pseudoword rhyming and visuospatial form processing are contrasted. We studied 201 adults from the Australian Epilepsy Project, including 94 with a history of seizures. A comparable pattern of activation and connectivity was observed in those with or without a history of seizures: The rhyming task produced robust activation in left FusG and perisylvian language areas. As predicted, connectivity from FusG to the left language cortex increased significantly during rhyming. We also observed significant increases in connectivity from the same FusG seed to the right parietal cortex during visuospatial form processing. The seizure group comprised a broader range of reading proficiency, and in this group better readers showed stronger increases in FusG connectivity to the left middle frontal gyrus and the medial prefrontal cortex. This suggests that visual text processing and articulatory sequencing are less tightly integrated in poor readers. By demonstrating how FusG connectivity shifts between language and visuospatial networks, our results provide new evidence that adaptive functional reorganisation is beneficial for cognitive performance.