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bioRxiv · 10.1101/2025.06.19.660638

Spectral imprint of structural embedding in effective connectivity

Greaves, M. D.·Novelli, L.·Pang, J. C.·Fornito, A.·Razi, A.
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Abstract

Neural fluctuations exhibit rich spectral profiles that reflects both local dynamics and structural (or anatomical) embedding. Yet, standard models of resting-state effective connectivity neglect structural embedding and assume uniformity in the timescales of regions endogenous fluctuations. We introduce a chromatic dynamic causal model (DCM) in which structural valency (or degree) modulates the spectral color of endogenous fluctuations. Specifically, we assume a linear mapping between regional structural valency and the spectral exponent of scale-free auto-spectra. Simulations show this mapping can emerge as a generic consequence of structural embedding under minimal coupling in a non-equilibrium regime. We show chromatic DCM reliably recovers ground-truth parameters across network sizes and noise conditions, outperforming standard spectral DCM. Applied to empirical data, chromatic DCM reveals that valency-exponent mappings vary across a cortical hierarchy, and that its parameters are conserved across a homologous network in humans, macaques, marmosets, and mice. These findings advance a generative account of structure-function coupling and expand the repertoire of biophysical mechanisms available for inference in effective connectivity modeling.

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Greaves, M. D., Novelli, L., Pang, J. C., Fornito, A., Razi, A.. 2025-06-25. Spectral imprint of structural embedding in effective connectivity. https://doi.org/10.1101/2025.06.19.660638

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