Using MRI scans, researchers have found 12 hubs of extraordinarily dense connections in the brain that are all tied together. Now they want to figure out why this special network exists.

That the brain is a powerful and complex organ is no mystery. But what researchers have begun to discover is that there are select areas of the brain that are so dense in their activity and interconnections that researchers have dubbed them the "rich clubs" of the brain.

A new study used a special type of MRI scan to map out the connections in the brains of 21 men and women. There are regions of the brain in which connectivity is extraordinarily dense -- that's been known for some time. What the present study set out to do was visualize how these dense regions might be connected to one another, possibly forming an elite network between these distinct and powerful regions of the brain.

They found exactly that: Twelve discrete hubs in the brain were interconnected with one another across hemispheres, forming what the researchers call a "rich club," distinct from the regular or "lower" network of the brain.

The work was carried out at Indiana University and at the Rudolf Magnus Institute of Neuroscience in the Netherlands. Author Olaf Sporns says that his team's findings show that "these regions are not only individually rich, they are forming a 'rich club.' They are strongly linked to each other, exchanging information and collaborating."

The group connectome, with the nodes and connections colored according to their rich-club participation.

Green represents few connections. Red represents the most. The Journal of Neuroscience, 2011.

But what's going on in this special network? That's a good question. "You sort of wonder what they're talking about when they're communicating with each other," said Sporns. "All these regions are getting all kinds of highly processed information, from virtually all parts of the brain."