Coherence in the brain unfolds across separable temporal regimes

TL;DR

This study reveals that language coherence in the brain involves distinct neural regimes for slow meaning integration and rapid reconfiguration, with regional preferences identified through high-resolution fMRI and language model annotations.

Contribution

It demonstrates that coherence during language comprehension is supported by separate neural processes for drift and shift, identified via novel encoding models using language model features and high-precision fMRI data.

Findings

Drift signals are prominent in default-mode network hubs.

Shift signals are evident in auditory and language cortex.

Distinct neural regimes support language coherence.

Abstract

To maintain coherence in language, the brain must satisfy key competing temporal demands: the gradual accumulation of meaning across extended context (drift) and the rapid reconfiguration of representations at event boundaries (shift). How these processes are implemented in the human brain during naturalistic listening remains unclear. Here, we tested whether both can be captured by annotation-free drift and shift signals and whether their neural expression shows distinct regional preferences across the brain. These signals were derived from a large language model (LLM) processing the narrative input. To enable high-precision voxelwise encoding models with stable parameter estimates, we densely sampled one healthy adult across more than 7 hours of listening to crime stories while collecting 7 Tesla fMRI data. We then modeled the feature-informed hemodynamic response using a regularized encoding framework validated on independent stories. Drift predictions were prevalent in default-mode network hubs, whereas shift predictions were evident bilaterally in the primary auditory cortex and language association cortex. Together, these findings show that coherence during language comprehension is implemented through distinct but co-expressed neural regimes of slow contextual integration and rapid event-driven reconfiguration, offering a mechanistic entry point for understanding disturbances of language coherence in psychiatric disorders.