Most human brain imaging studies have employed magnetic resonance imaging (MRI) to examine the gross anatomy of the brain or functional MRI to detect which regions are active during specific tasks. But advances in brain imaging technologies in recent years, as well as growing computing power, have made it possible to look at the fine wiring connecting brain regions. “If we want to understand the brain, we need to know what individual areas are doing and how they talk to each other,” says Russell Poldrack, director of the Imaging Research Center at the University of Texas at Austin. “Moving from examining how 120 brain areas operate on their own to determining how those 120 areas interact with each other increases the complexity by an order of magnitude, and the scale you need to address the problem also goes up.”
Van Essen and his collaborators plan to scan participants using two relatively recent variations on MRI. Diffusion imaging, which detects the flow of water molecules down insulated neural wires, indirectly measures the location and direction of the fibers that connect one part of the brain to another. Functional connectivity, in contrast, examines whether activity in different parts of the brain fluctuates in synchrony. The regions that are highly correlated are most likely to be connected, either directly or indirectly. Combining both approaches will give scientists a clearer picture. Collaborators at the University of Minnesota and Massachusetts General Hospital are optimizing existing scanners with new magnets and custom analysis programs so that they are better suited to detecting these circuits.
“This will be a landmark study,” says Robert Williams, a neuroscientist at the University of Tennessee, in Memphis. “I think it will have the same kind of impact on neuroscience that the Human Genome Project had on human genetics, providing a strong foundation for other work.”