Human brain turns out to be folding of 2D sheets of parallel neuronal fibers For a long time it was thought that the brain was a mass of tangled wires, but researchers recently found that its fibers are actually set up like a chess board, crossing at right-angles .
What’s more, this grid structure has now been revealed in amazing detail as part of a brain imaging study by a new state-of-the-art magnetic resonance imaging (MRI) scanner.
Van Wedeen, of Massachusetts General Hospital (MGH), who led study, said: ‘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.
Thomas R Insel, the director of the National Institute for Mental Health, said: ‘Getting a high-resolution wiring diagram of our brains is a landmark in human neuroanatomy.
‘This new technology may reveal individual differences in brain connections that could aid diagnosis and treatment of brain disorders.’
The Connectom MRI scanner was installed at MGH last year and can visualise the networks of criss-crossing fibers – by which different parts of the brain communicate with each other – in 10-fold higher detail than conventional scanners, according to Wedeen.
He said: ‘This one-of-a-kind instrument is bringing into sharper focus an astonishingly simple architecture that makes sense in light of how the brain grows. The wiring of the mature brain appears to mirror three primal pathways established in embryonic development.’
As the brain gets wired up in early development, its connections form along perpendicular pathways, running horizontally, vertically and transversely.This grid structure appears to guide connectivity like lane markers on a highway, which would limit options for growing nerve fibers to change direction during development.
If they can turn in just four directions: left, right, up or down, this may enforce a more efficient, orderly way for the fibers to find their proper connections – and for the structure to adapt through evolution, suggest the researchers.
Obtaining detailed images of these pathways in human brain has long eluded researchers, in part, because the human cortex, or outer mantle, develops many folds, nooks and crannies that obscure the structure of its connections.
Although studies using chemical tracers in neural tracts of animal brains yielded hints of a grid structure, such invasive techniques could not be used in humans.
It’s thought that with previous technology 25 per cent of the brain’s structure was revealed – the new scanner shows 75 per cent of it.
‘Before, we had just driving directions. Now, we have a map showing how all the highways and byways are interconnected,’ said Wedeen. ‘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.’