Diffusion spectrum imaging finds activity hub in brain

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New imaging techniques, like diffusion spectrum imaging, focused on the brain’s white matter, are filling in a dimension of human brain function that has been relatively unknown, according to a report published in PLoS Biology.

According to the report, 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.

The New York (NY) Times reported that previously, scientists have used MRI to identify peaks and valleys of neural activity when people make decisions, react to frightening images or relive painful memories. However, such studies did not reveal much about the underlying neural networks involved. The new findings, while not conclusive, essentially give scientists a wiring diagram that they can test and refine.

Researchers from the University of Lausanne in Switzerland, Harvard and Indiana University, studied the brains of five healthy male volunteers using diffusion spectrum imaging, which 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, according to the NY Times.

The hubs clustered in each man’s brain, in a region about the size of a palm, were centered atop the cortex like a small skullcap.

“We haven’t had a comprehensive map of the brain showing what is connected to what, and you really need the whole thing before you can ask certain questions, like what happens if activity is clogged up at one of the hubs? How does that effect function?” Olaf Sporns, a psychologist at Indiana University in Bloomington, and senior author of the paper, told the NY Times.

The researchers performed a standard functional MRI scan on the participants to check their findings. They measured which areas of their gray matter were most active when the men were at rest. The results revealed that the same areas overlapped with the network hubs that the group had already identified.

Sporns said continued research should help produce a complete and detailed neural wiring diagram, what he called the “connectome” of the brain. “We hope we can get to a place where we have, in effect, a brain simulator, in the same way we have computer models that can simulate the climate so we can simulate activation patterns we see in clinical cases,” like psychiatric problems and brain injuries, he concluded.

The report’s co-authors were Patric Hagmann, Leila Cammoun, Xavier Gigandet, Reto Meuli, Christopher J. Honey and Van J. Wedeen.