Feb. 19, 2018

At the gates of the brain’s rich club

There is a group of densely interconnected regions in the brain known as the ‘rich club’ whose purpose is speculated to be a ‘central high capacity backbone for brain communication’.

New work from researchers associated with and within the Human Brain Project has explored the role of this collection of brain areas in deeper detail, particularly the way it communicates with other brain areas.

Using a combination of functional magnetic resonance imaging (fMRI) data and computational modelling the study found evidence to support the hypothesis that the rich club might serve as a gated relay for whole-cortex communication.

“Taken together, our results provide further support for the notion that the rich club serves as a central workspace wherein peripheral brain regions compete for the establishment of communication channels among them,” says the paper.

 “In this context, the rich club might act as a gate furthering communication among a winning set of task-relevant peripheral regions while intercepting signals from competing regions. During rest, the gate should largely be closed and the rich club should thus receive more input from peripheral regions than sending output to these regions,” the paper says.

Indeed, the study found that during rest the rich club impeded communication between peripheral brain regions. By measuring ‘effective connectivity’ (EC) the study authors found that during rest the total outgoing EC from the rich club was half of its total incoming EC.

In contrast, during task performance the rich club passed on much more of this input.

The authors say the rich club is always listening to the entire cortex, and as task demands increase the network dynamics become faster in order to process information more efficiently.

“At the same time, the rich club increases its outgoing effective connectivity to establish communication among task-relevant peripheral regions and prevent global decoupling (a consequence of faster dynamics). With a transition to task performance, the rich club thus supports the interplay of a set of task-relevant peripheral regions as required for higher cognition.”

 

Article written by Greg Meylan. Email: gregory.meylan@epfl.ch

 

Brain regions are classified as rich club or peripheral regions. Communication occurs within each set of regions (black arrows) as well as between regions of different sets. (a) During rest, the rich club receives a fair amount of input from the periphery (purple arrows) but provides only little output back to peripheral regions (red arrows). (b,c) During task performance, the rich club increases the output it projects to the periphery. The specific peripheral targets of increased rich club output may depend on which task is currently being performed.

Image and caption taken from the paper.