Far from being a haphazard tangle of circuitry, the human brain is organised in a logical, simple 3D grid structure, scientists report.
Connections in the brain appear to crisscross at right angles, with no diagonals, much like well-organised city streets.
This elegant simplicity was discovered by researchers who used a special type of MRI scanner to examine the brains of humans and four different types of monkeys. The new Connectom diffusion MRI technology provides 10 times greater detail than conventional scanners, the team explained.
The study was funded by the U.S. National Institute of Mental Health (NIMH) and published in the journal Science.
"Far from being just a tangle of wires, the brain's connections turn out to be more like ribbon cables - folding 2D sheets of parallel neuronal fibers that cross paths at right angles, like the warp and weft of a fabric," study author Dr. Van Wedeen, of Massachusetts General Hospital, A.A. Martinos Center for Biomedical Imaging and the Harvard Medical School, explained.
Brain constantly rewiring
The new, high-resolution look at the brain's wiring is a milestone in learning more about its anatomy, added institute director Dr. Thomas Insel, and "this new technology may reveal individual differences in brain connections that could aid diagnosis and treatment of brain disorders."
Primates appear to share this basic neurological structure, Wedeen added. "This grid structure is continuous and consistent at all scales and across humans and other primate species," he said.
The brain may be so flexible that it constantly rewires itself as the need arises, Wedeen added. The authors believe that, during development, the brain organises itself along perpendicular pathways that run horizontally, vertically and transversely. This type of organisation would guide growing nerve fibres to find suitable connections, and also change as evolution demanded it.
"Before, we had just driving directions. Now, we have a map showing how all the highways and byways are interconnected," he explained. "Brain wiring is not like the wiring in your basement, where it just needs to connect the right endpoints. Rather, the grid is the language of the brain and wiring and re-wiring work by modifying it."
Anatomy of the brain
The American Association of Neurological Surgeons has more about brain anatomy.
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