Exploring the role of the rich club in network control of neurocognitive states

We present a systematic analysis of the rich club as a possible control center of brain dynamics. Contrary to research stressing control properties of the rich club, our results indicate that the rich club and high-degree regions were not involved in optimally controlling the human connectome for a set of data-driven and task-evoked patterns of activity. Indeed, low-degree peripheral regions were more suited towards this. Findings were stable across group-level and individual-level rich club definitions, various cognitively meaningful brain state transitions, and different parameter settings. A regions contribution to optimal control processes was associated with its affiliation with certain intrinsic connectivity networks and its position on the secondary, but not primary, cortical gradient. These results do not negate an integratory role of the rich club, but merely question its proposed role as a driver of control. Indeed, if it would inhabit such a role, we would have expected opposite results. Our findings fit with a position describing the rich club as a passive "data-highway" which, by means of its high connectivity, can be easily controlled by peripheral regions and thus facilitate relevant communication channels between them. We call for methodological expansions of the control theoretical toolbox allowing for elaborations on the temporal dynamics of control processes.