The crucial role of the left inferior frontal gyrus (BA44) in synergizing syntactic structure and information structure during sentence comprehension

• Left IFG (BA44), BA6, and pSTG/pMTG specialize in syntactic processing. • Right IFG, IPS, and left IFG (triangular part) process information structure. • Left IFG (BA44) integrates syntactic and information structures. • Findings show the interplay of syntactic and information structures in language comprehension. This study examines the neural mechanisms behind integrating syntactic and information structures during sentence comprehension using functional Magnetic Resonance Imaging. Focusing on Japanese sentences with canonical (SOV) and non-canonical (OSV) word orders, the study revealed distinct neural networks responsible for processing these linguistic structures. The left opercular part of the inferior frontal gyrus, left premotor area, and left posterior superior/middle temporal gyrus were primarily involved in syntactic processing. In contrast, the right inferior frontal sulcus, bilateral intraparietal sulci, and the left triangular part of the inferior frontal gyrus were linked to information structure processing. Importantly, the left opercular part of the inferior frontal gyrus (BA44) played a crucial role in integrating these structures during the later stages of comprehension, particularly when processing the second noun phrase. These findings enhance our understanding of the complex interplay between syntactic and information structures in language comprehension.