In an astonishing new study, scientists at the National Institutes of Health (NIH), have imaged human and monkey brains and found… well, the image above says it all. It turns out that the pathways in your brain — the connections between neurons — are almost perfectly grid-like.

It’s rather weird: If you’ve ever seen a computer ribbon cable — a flat, 2D ribbon of wires stuck together, such as an IDE hard drive cable — the brain is basically just a huge collection of these ribbons, traveling parallel or perpendicular to each other. There are almost zero diagonals, nor single neurons that stray from the neuronal highways. The human brain is just one big grid of neurons — a lot like the streets of Manhattan, minus Broadway, and then projected into three dimensions.

This new imagery comes from a souped-up MRI scanner that uses diffusion spectrum imaging to detect the movement of water molecules within axons (the long connections made by neurons). The brain has always been very difficult to image because of the wrinkly nature of the cerebral cortex that surrounds the brain — but this new MRI scanner finally has the ability to peer through the folds. Members of the Human Connectome Project first analyzed monkey brains (pictured above) — which are very similar to human brains — and then used their findings to tweak the MRI scanner to improve its imaging of human brains (pictured below). A connectome is a complete map of the connections and pathways in a brain — basically, the neuronal version of your DNA genome.

“Before, we had just driving directions. Now, we have a map showing how all the highways and byways are interconnected,” says Van Wedeen, a member of the Human Connectome Project. “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.”

Curiously, it seems like this network of highways and byways is laid out when we’re still an early fetus. At a very early stage, our brains form three “primal pathways” that traverse our brains horizontally, vertically, and transversely. The NIH scientists now think that those early connections act as markers, forcing the continued growth of an orderly, grid-like structure. Apparently such a setup is more amenable to evolutionary adaptation, too.

As for the actual implications of such a discovery… well, in the long term we are looking at a much greater understanding of consciousness, intelligence, and mental illness. After cracking the genome, there is now a lot of emphasis on unearthing the mysteries of the connectome. We still know almost nothing about how the brain’s structure translates into its incredibly complex and powerful functionality — but this study is an important step towards a scientific model of the brain.

In an unrelated project, MIT has been trying to crowdsource analysis of the human connectome by getting people to play a game of “connect the neurons.” MIT has also recently pinpointed the location of individual memories in the brain.

Read more at NIH