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The role of node dynamics in shaping emergent functional connectivity patterns in the brain

Forrester, M.; Crofts, J. J.; Sotiropoulos, S. N.; Coombes, S.; O'Dea, R. D.

Authors

J. J. Crofts

S. N. Sotiropoulos

R. D. O'Dea



Abstract

The contribution of structural connectivity to functional brain states remains poorly understood. We present a mathematical and computational study suited to assess the structure-function issue, treating a system of Jansen-Rit neural-mass nodes with heterogeneous structural connections estimated from diffusion MRI data provided by the Human Connectome Project. Via direct simulations we determine the similarity of functional (inferred from correlated activity between nodes) and structural connectivity matrices under variation of the parameters controlling single-node dynamics, highlighting a non-trivial structure-function relationship in regimes that support limit cycle oscillations. To determine their relationship, we firstly calculate network instabilities giving rise to oscillations, and the so-called 'false bifurcations' (for which a significant qualitative change in the orbit is observed, without a change of stability) occurring beyond this onset. We highlight that functional connectivity (FC) is inherited robustly from structure when node dynamics are poised near a Hopf bifurcation, whilst near false bifurcations, structure only weakly influences FC. Secondly, we develop a weakly-coupled oscillator description to analyse oscillatory phase-locked states and, furthermore, show how the modular structure of FC matrices can be predicted via linear stability analysis. This study thereby emphasises the substantial role that local dynamics can have in shaping large-scale functional brain states. AUTHOR SUMMARY Patterns of oscillation across the brain arise because of structural connections between brain regions. However, the type of oscillation at a site may also play a contributory role. We focus on an idealised model of a neural mass network, coupled using estimates of structural connections obtained via tractography on Human Connectome Project MRI data. Using a mixture of computational and mathematical techniques we show that functional connectivity is inherited most strongly from structural connectivity when the network nodes are poised at a Hopf bifurcation. However, beyond the onset of this oscillatory instability a phase-locked network state can undergo a false bifurcation, and a n o p e n a c c e s s j o u r n a l Citation: M. Forrester, J. J. Crofts, S.N. Sotiropoulos, S. Coombes and R.D. O'Dea (2018) The role of node dynamics in shaping emergent functional connectivity patterns in the brain Network Neuroscience

Journal Article Type Article
Publication Date Feb 3, 2020
Journal Network Neuroscience
Electronic ISSN 2472-1751
Publisher Massachusetts Institute of Technology Press
Peer Reviewed Peer Reviewed
APA6 Citation Forrester, M., Crofts, J. J., Sotiropoulos, S. N., Coombes, S., & O'Dea, R. D. (2020). The role of node dynamics in shaping emergent functional connectivity patterns in the brain. Network Neuroscience, https://doi.org/10.1162/netn_a_00130
DOI https://doi.org/10.1162/netn_a_00130
Keywords Structural connectivity; functional connectivity; neural mass model; coupled oscilla- tor theory; Hopf bifurcation; false bifurcation
Publisher URL https://www.mitpressjournals.org/doi/abs/10.1162/netn_a_00130

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