Key result
Empirical human connectomes require substantially less global excitation to trigger cortical ignition versus randomized surrogates.
Why the study?
The intrinsic propensity of cortical regions to sustain an ignited state and its dependence on the topological organisation of the structural connectome is not fully understood.
The topology of human structural connectivity, specifically its weighted core-shell organization, may be attuned to support enhanced ignition dynamics.
No immediate clinical implications; leaves open whether human connectome topology optimizes ignition in computational models.
The capability of cortical regions to flexibly sustain an "ignited" state of activity has been discussed in relation to conscious perception or hierarchical information processing. Here, we investigate how the intrinsic propensity of different regions to get ignited is determined by the specific topological organisation of the structural connectome. More specifically, we simulated the resting-state dynamics of mean-field whole-brain models and assessed how dynamic multistability and ignition differ between a reference model embedding a realistic human connectome, and alternative models based on a variety of randomised connectome ensembles. We found that the strength of global excitation needed to first trigger ignition in a subset of regions is substantially smaller for the model embedding the empirical human connectome. Furthermore, when increasing the strength of excitation, the propagation of ignition outside of this initial core-which is able to self-sustain its high activity-is way more gradual than for any of the randomised connectomes, allowing for graded control of the number of ignited regions. We explain both these assets in terms of the exceptional weighted core-shell organisation of the empirical connectome, speculating that this topology of human structural connectivity may be attuned to support enhanced ignition dynamics.
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Castro et al. (2020) studied Healthy (n=5). Empirical human connectome topology vs. Randomised surrogate connectomes was evaluated on Ignition point (G-). The empirical human connectome requires a substantially lower strength of global excitation to trigger cortical ignition compared to randomised surrogate connectomes.
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