Scientists Identify the Brain's Activity Hub

The outer layer of the brain, the reasoning, planning and self-aware region known as the cerebral cortex, has a central clearinghouse of activity below the crown of the head that is widely connected to more-specialized regions in a large network similar to a subway map, scientists reported Monday.

The new report, published in the free-access online journal PLoS Biology, provides the most complete rough draft to date of the cortex's electrical architecture, the cluster of interconnected nodes and hubs that help guide thinking and behavior. The paper also provides a striking demonstration of how new imaging techniques focused on the brain's white matter -- the connections between cells, rather than the neurons themselves -- are filling in a dimension of human brain function that has been all but dark.

In previous studies, scientists have used magnetic resonance imaging to identify peaks and valleys of neural activity when people are doing various things, like making decisions, reacting to frightening images or reliving painful memories. But these studies, while provocative, revealed virtually nothing about the underlying neural networks involved -- about which brain regions speak to one another and when. Previous estimates of network structure, based on such imaging, have been sketchy.

The new findings, while not conclusive, give scientists what is essentially a wiring diagram that they can test and refine.

"This is just about the coolest paper I've seen in a long time, and forward-looking in terms of where the science is going," said Dr. Marcus E. Raichle, a professor of neurology and radiology at Washington University in St. Louis, who was not involved in the research. He added, "They've found in the brain what looks like a hub map of the airline system for the United States."

In the study, a collaboration that included the University of Lausanne in Switzerland, Harvard and Indiana University, researchers studied the brains of five healthy male volunteers using a new technique called diffusion spectrum imaging. The technique allows scientists to estimate the density and orientation of the connections running through specific brain locations. Using a computer analysis of the results, the researchers ranked the busiest spots on the cortex in order, by the number of connections they had. Finally, they plotted those spots back onto the brain maps of the five volunteers. ...

•	Scientists Identify the Brain's Activity Hub The New York Times, Tuesday, July 1, 2008 Byline: Benedict Carey

	Story also ran in 1 others:  International Herald Tribune (France)