Multiple Nested Distributed Language Networks in the Human Brain

Recent research has illuminated the complex structure of language networks within the human brain. Precision functional mapping across three separate cohorts of individuals, totaling 22 participants scanned in 216 MRI sessions, has revealed two distinct networks. These networks are positioned in the left hemisphere of the brain, with the intermediate language network (intLANG) and the association language network (aLANG) demonstrating a nested structure.

intLANG is closely linked to precentral speech areas and the Sylvian parietal-temporal area (Spt). In contrast, aLANG envelops intLANG and expands into higher-order prefrontal and temporal association cortices. Remarkably, both networks can be understood as functional connectivity emanating from cerebellar regions, suggesting their segregation into distinct, brain-wide systems.

Functional distinctions between these networks were further elucidated through task-based analyses. The intLANG network was found to respond strongly during tasks emphasizing phonology, such as rhyme judgments and nonword reading. Conversely, the aLANG network showed a preference for meaning-based sentence processing.

These findings contribute to our understanding of human language processing, illustrating that the brain engages in nested distributed networks, each specialized for specific aspects of language. A lower-order network, intLANG, is dedicated to phonological processing, while a surrounding association network, aLANG, is implicated in higher-order syntax and semantics.

This hierarchical organization mirrors similar patterns observed in other brain systems, pointing to a shared hierarchical motif that fosters specialized cognitive functions across the human brain.