THE human brain is a fantastic maze of connections, a vast network of networks that circulates information and determines how we think and act. One of the many big puzzles left in neurology is working out which parts of the brain are connected 鈥� and how the networks function.
That鈥檚 why top neuroscientist Olaf Sporns of Indiana University at Bloomington and his team are hoping for some lively debate about their new blueprint to map those connections. Sporns is calling it 鈥渢he human connectome鈥� after the billion-dollar human genome project, but it鈥檚 bound to be far more sophisticated.
Why? Well, the genome is one-dimensional, while the connectome will be four-dimensional (three space, one time). The information needed to build the connectome is also far more elusive. Our brains contain roughly 1011 neurons, with an estimated 1014 possible connections. The magnitude of these numbers makes it impossible for the connectome to map the brain at the level of single neurons and synapses. Luckily, that may not be necessary because nerve cells tend to act in groups.
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What will the connectome look like? At first, it will be a huge set of numbers from which cognitive patterns can be deduced. Input the coordinates of two brain regions and the connectome will give the probability of those two parts talking to one another. The coordinates refer to voxels (3D pixels), which is useful because it鈥檚 how neuroscientists map the brain, so the connectome can be cross-referenced to other data. But in future, with the right technology, we could build a dynamic 4D model with the brain鈥檚 connections operating in real time. Just think: one little thought, and the model would light up like a Christmas tree!
鈥淭he brain is a maze of connections, a vast network of networks鈥�
So how much is known already? There are a few precedents: large-scale connection patterns have been mapped for animal brains such as the macaque, cat and rat. But for human connections, researchers will need sophisticated imaging techniques that show how the brain鈥檚 anatomy relates to its dynamic function. For that, they鈥檒l build on existing techniques such as diffusion tensor imaging, functional MRI and EEGs.
They鈥檒l also need the snazzy software used to map connections in the web and other large networks. Not to mention computers such as the giant 10 petaflop baby that Japan is planning.
The pay-off? Oh, just a few useful things such as finding out much more about how the different regions of the brain interact when we think or act, what injuries to particular regions do, and how our cognitive networks differ from those of other species.
Not surprisingly, the connectome will demand a worldwide effort by anatomists, brain imagers and computational scientists. And more billions than the genome project. Sporns thinks a first draft of the connectome could be ready in a few years. Watch this space.
