Evidence of fronto-temporal interactions for strategic inference processes during language comprehension

We investigated how readers strategically infer context-appropriate information on the basis of the presented text and their world knowledge during passage reading. In the main experimental condition, participants were instructed to read short passages and to predict the development of the situation described in each passage during reading. To accomplish this task, we assumed that participants need to draw strategic inferences relevant to the contexts. Comparing this condition with a passage-reading condition without prediction, we found out that the left anterior prefrontal cortex (aPFC) in Brodmann area 9/10 and the left anterior ventral inferior frontal gyrus (vIFG) in Brodmann area 47 elicited increased hemodynamic responses. These two regions are probably critical in coherence evaluation and in drawing strategic inferences. Additionally, we used dynamic causal modelling (DCM) to investigate the fronto-temporal interactions induced by the experimental conditions. Ten models with different plausible ways to modulate the connections between frontal and temporal regions were compared. The DCM results showed a consistent conclusion: The connectivity between the left posterior superior temporal sulcus (pSTS) and the left dorsal lateral inferior frontal gyrus (dIFG) were enhanced when participants made inferential predictions during reading. The results support the role of top-down influences mediated by the neural pathways between dIFG and pSTS in retrieving strategic inferences. With these findings we discuss functional roles of aPFC, vIFG and dIFG-pSTS connections in drawing strategic inferences.