Characteristics of the Involvement of Hidden Nodes in the Activity of Human Brain Systems Revealed on fMRI Data

Abstract

Currently, it is generally accepted that brain functioning is based on the systemic principle. At the same time, knowledge about the principles and mechanisms of the brain system functioning remains scarce. In the present work, these principles were studied within the framework of ideas about the so-called “hidden” nodes of the brain systems. Previously, according to fMRI data, it was shown that some brain structures could be involved in work without changing their energy consumption (reflected by the blood oxygenation level-dependent signal). Their involvement was found only due to a change in the long-range functional connectivity. An analysis of the systemic brain activity using functional connectivity data makes it possible to reveal “hidden” nodes that are inaccessible to detection using the standard “activation” approach. This work aimed to clarify the extent and nature of the involvement of “hidden” nodes in the brain maintenance of various task activities using open fMRI data from the Human Connectome Project. It has been shown that the brain systems ensuring the current activity are provided with a much larger number of nodes than was previously believed, and the overwhelming majority of them are “hidden”. For the first time, this result clearly shows the actual scale of the brain systems providing current activity. The mental activity is actually provided by the work of almost the entire brain and not a minor part of it, as is usually observed in functional tomographic studies. As a result, it is shown that the idea of the existence of “hidden” nodes is confirmed by analyzing the activity of the human brain at the macro-level and shows similarities with the characteristics of the micro-level activity of individual neuronal populations, confirming the previously formulated neurophysiological ideas about the systemic organization of brain activity.