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Hank briefs us on a fascinating project that aims to map the anatomical and functional pathways of the brain - a neural network called the human connectome.

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Now, you've heard of the human genome. Please allow me to introduce you to the human Connectome, the first ever not-quite-finished map of the human brain.

Our brains, like the rest of our nervous system, are made up mostly of neurons. Neurons are basically like a normal cell, with the cell body and the nucleus and all the usual organelles. But one thing that makes them different is the long branches coming off them called axons. These serve as pathways that allow signals to travel from neuron to neuron.

The outermost layer of our brains, called the gray matter, is responsible for all of our cognition and it mostly contains neuron cell bodies. But deeper, beneath that, is the white matter, which sends signals from one part of the brain to another. It's mostly made up of axons that act like your brain's wiring.

Until recently, neurologists thought that white matter was just kind of like a plate of spaghetti, just a bunch of wires randomly connecting different parts of the brain. But in 2005, neurologists with the National Institute of Health and a number of other US universities set out to make a map of all of our neural connections for the first time. They called that map the human Connectome.

Their research uses a one-of-a-kind MRI scanner so sensitive that it can detect the movement of water inside individual neuron fibers, to show where they are. And then it uses a resolution technique called diffusion spectrum imaging to see in what direction those fibers are oriented. To get pictures like this, a traditional MRI machine would have to have a test subject sitting in the machine for more than seven hours. Now, they can take these pictures in a matter of minutes.

What they're finding, is that instead of being a bunch of neurological spaghetti, these fibers are actually organized into an orderly three-dimensional grid, with fibers running up and down and left and right with no diagonals or tangles. Scientists describe it as sort of like the layout of a big city, with streets running in two directions and elevators in buildings going up and down. And in the flat areas of this grid, the fibers overlap at precise ninety-degree angles, weaving together a lot like in a fabric.

The simplicity here is what's baffling. The brain is, without a doubt, one of the most complicated and amazing structures in the world - probably in the universe. It's so mysterious and complicated that scientists are surprised to find so much order. Some researchers think that the grid model might be hiding some more complex structures and indeed, the scanner hasn't penetrated the outer layers of the brain yet. Only the main roads, at this point.

But this still might answer lots of questions in other branches of biology, like the evolution of the human brain. If animal brains are built around the same basic grid, it becomes a lot more understandable how a fish's brain could be related to a human brain. As organisms evolve, functions are simply added as they get more modified and more complex, but the basic layout remains similar.

The human Connectome project should be finished within the next five years and you can learn more about it at the links below. Keep an eye out for more brains in the news. Thank you for watching this episode of SciShow. If you have questions, ideas, or suggestions for us, please leave them in the comments below, or on Facebook or Twitter. And if you want to continue getting smarter with us, go to SciShow on YouTube and subscribe.