pickens's Journal: Decoding the Brain's Network of Neurons

New technologies that allow scientists to trace the fine wiring of the brain more accurately could soon generate a complete wiring diagram--including every tiny fiber and miniscule connection--of a piece of brain. "The brain is essentially a computer that wires itself up during development and can rewire itself," says Sebastian Seung, a computational neuroscientist at MIT. "If we have a wiring diagram of the brain, we might be able to understand how it works." With an estimated 100 billion neurons and 100 trillion synapses in the human brain, creating an all-encompassing map of even a small chunk is a daunting task. Winfried Denk, a neuroscientist at the Max Planck Institute for Medical Research in Heidelberg, Germany, has developed a new technique to make more fine-scaled wiring maps using electron microscopy. Starting with a small block of brain tissue, the researchers bounce electrons off the top of the block to generate a cross-sectional picture of the nerve fibers in that slice. They then take a very thin--30-nanometer--slice off the top of the block and repeat the process going through slice by slice to trace the path of each nerve fiber. "Repeat this [process] thousands of times, and you can make your way through maybe the whole fly brain," says Denk. The researchers train an artificial neural network to emulate the human tracing process to speed the process about one hundred- to one thousand-fold.