A novel use of MR has set the stage for neuroscientists to unravel the trillions of neural connections in the human brain and with them a fundamental understanding of brain function and dysfunction. In a multinational research project, this technique, diffusion spectrum imaging, was used to document neural fibers running through the human cortex, the highly furrowed part of the brain responsible for memory, attention, perceptual awareness, thought, language, and consciousness. In their study of five healthy subjects, the U.S. and Swiss researchers uncovered a densely packed region in the cortex that appears to serve as the central hub for cortical activity. They found that this neural core in the medial posterior portion of the cortex straddles the two hemispheres of the brain."Researchers have been interested in this part of the brain for other reasons," said Olaf Sporns, Ph.D., a coauthor of the study published June 30 in PLoS Biology and professor of psychological and brain sciences at Indiana University. "For example, when you're at rest, this area uses up a lot of metabolic energy, but until now it hasn't been clear why," he said.MRI has identified this as a major region of activity during perception and cognition activities. The researchers from Indiana University and Harvard Medical School and the University of Lausanne and Ecole Polytechnique Fédérale de Lausanne in Switzerland conducted fMRI studies of the same volunteers to compare brain activity with the fiber networks mapped using DSI. "It turns out they're quite closely related," Sporns said. "We can measure a significant correlation between brain anatomy and brain dynamics." Having made this correlation possible, DSI could serve as the means for developing a fundamental understanding of the brain. "If we know how the brain is connected, we can predict what the brain will do," Sporns said. Researchers have been using other forms of diffusion imaging for some time to create gradient maps that indicate the diffusion of water molecules through brain tissue. Diffusion tensor imaging, another type of mapping, may be used with fMRI or in place of it to show the paths taken by brain fibers so that critical tracts can be avoided during neurosurgery. Diffusion imaging may also be used to identify areas of the brain associated with thought processes. Diffusion tensor imaging and fMRI do so indirectly by registering activities associated with those brain areas. DSI provides the raw data needed to assemble computer models depicting the fibers themselves, according to Sporns.Its use in the study of five human brains barely hints at what is yet to come. The researchers are planning to expand their work with more subjects to examine whether and how brain connectivity changes with advancing age or during the course of disease and dysfunction. The ultimate goal is to build large-scale computational models of the human brain."These models will help us understand processes that are difficult to observe, such as disease states and recovery processes to injuries," Sporns said.For more information from the Diagnostic Imaging archives:Brain stays cools as jazz man jamsBrain imaging study uncovers neurophysiology of drunken behaviorBelief in Gold gets blood oxygen level-dependent lookfMRI bolsters diagnosis, management of autismNavigational MRI charts language map of brain
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| High-resolution map of human cerebral cortex, created using MR-based diffusion spectral imaging, identifies single network core that could be key to workings of both hemispheres of brain. (Provided by Indiana University) |
