Excitatory delay-coupling explains in-phase and antiphase functional connectivity

Authors

Omurtag, A., Dragomir, A., Crofts, J., Lytton, W. W.

Abstract

Coordinated oscillatory activity between brain regions underpins cognition, yet the phase relationships governing this coordination remain poorly understood. Using scalp EEG from 31 participants performing a motor learning task, we show that inter-site phase clustering occurs predominantly at in-phase or antiphase relationships, with the transition between them governed by conduction delay. Homologous interhemispheric pairs remain in-phase despite long distances, consistent with faster callosal conduction. A minimal model of two delay-coupled excitatory populations reproduces these features without parameter tuning; stability analysis shows that in-phase and antiphase oscillations arise from competing instabilities, with delay determining which dominates. Task performance shifts a frontoparietal network toward in-phase connectivity, a modulation captured by the Phase Relationship Index (PRI) but missed by conventional clustering metrics. Preliminary evidence from independent datasets suggests these patterns generalise. These findings challenge the assumption that zero-lag connectivity reflects volume conduction, offer a mechanistic account linking conduction delay to phase organisation, and introduce PRI as a metric sensitive to functionally relevant connectivity changes invisible to existing measures.

Preprint server: bioRxiv
The authors list and abstract were imported from bioRxiv on 20 Jul 2026.

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