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bioRxiv · 10.64898/2026.06.03.729880

Theta phase and theta-gamma coupling organise the spoken language network

Akkad, H.·Bush, D.·Seymour, R.·Twomey, T.·Pelke, S.·Ondobaka, S.·Bestmann, S.·Crinion, J.
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Abstract

Speech production requires rapid coordination of conceptual and lexical processes across distributed cortical networks, yet the neurophysiological mechanisms enabling this coordination remain poorly understood. Oscillatory coupling has emerged as a candidate mechanism for coordinating neural activity across spatial scales. Here, we used whole-head magnetoencephalography during overt picture naming to test how phase and phase-amplitude coupling organise neural dynamics preceding articulation. We show that theta (4-8 Hz) phase coupling increases within two functionally distinct networks: a ventral occipito-temporal network supporting object recognition and a medial fronto-temporal network supporting semantic-lexical retrieval. These networks converged in the right fusiform gyrus beyond chance levels, identifying a candidate integration hub. In parallel, whole-brain analysis of theta-gamma (4-8 Hz, 40-100 Hz) phase-amplitude coupling revealed selective increases in the left inferior frontal and fusiform gyri during picture naming relative to control. Mixed-effects modelling further showed that coupling in the left fusiform correlates with trial-level response times during naming but not control trials. Together, these findings reveal the oscillatory mechanisms that implement known functional specialisation in the spoken language network; theta phase coupling coordinates distributed recognition and retrieval streams, while theta-gamma coupling modulates local computations within core word production nodes. By defining an oscillatory framework for real-time speech production, this work advances mechanistic understanding of the spoken language network and identifies frequency- and region-specific targets for neuromodulation of language production disorders. HighlightsO_LIDistinct oscillatory mechanisms support distributed and local language production processes C_LIO_LITheta phase-coupling distinguishes object recognition and word retrieval networks C_LIO_LITheta-gamma coupling increases locally in core language regions C_LIO_LIIncreases in theta-gamma coupling scale with trial-by-trial naming speed C_LI

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Akkad, H., Bush, D., Seymour, R., Twomey, T., Pelke, S., Ondobaka, S., Bestmann, S., Crinion, J.. 2026-06-04. Theta phase and theta-gamma coupling organise the spoken language network. https://doi.org/10.64898/2026.06.03.729880

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