Conciousness and healthy brain function appear to emerge not from neurons, but from the networks linking them together. Scientists are only just beginning to map that complex network and understand how it works. Whereas previous studies have shown that some regions of the human brain have more connections than others, until now no one has known exactly how those "hubs" interact.



A new study, published November 2 in The Journal of Neuroscience, used MRI scans to map brain activity in 21 people. They found that the areas with the most connections—the hubs—were more strongly connected to one another than to other, less popular regions.



The researchers liken the favored networks to a country club setting, in which people with a great number of social connections bond with other connection-rich socialites. In the brain, the socialites (the hubs with the most connections, shown in red in the image) included the regions that aggregate and process many kinds of information—the superior frontal and superior parietal cortex, for example, as well as the subcortical hippocampus, putamen and thalamus.



The close-knit organization of these central hubs helps the brain stay resilient to damage. The architecture is like that found in well-designed electrical power grids—a tight knit means that if one power plant cannot produce enough energy, another one can compensate. Similarly, the authors wrote, the brain's rich-club connectivity might provide resilience "in case of malfunction of one of its key hubs."



The strong connections also mean that damage to a rich-club hub could have more devastating impacts than damage to a less connected area. Because network abnormalities are thought to underlie several disorders—including Alzheimer's, amyotrophic lateral sclerosis, Parkinson's, schizophrenia and autism—the researchers hope that a better understanding of the brain's networks can untangle new ways to understand and treat disease.



—Sarah Fecht