Source: NYTimes, Jan 2015
device that imaged brain tissue with enough resolution to make out the connections between individual neurons. But drawing even a tiny wiring diagram required herculean efforts, as people traced the course of neurons through thousands of blurry black-and-white images. What the field needed, Tank said, was a computer program that could trace them automatically — a way to map the brain’s connections by the millions, opening a new area of scientific discovery. For Seung to tackle the problem, though, it would mean abandoning the work that had propelled him to the top of his discipline in favor of a highly speculative engineering project.
Seung published a paper in the prestigious journal Nature, demonstrating how the brain’s neural connections can be mapped — and discoveries made — using an ingenious mix of artificial intelligence and a competitive online game. Seung has also become the leading proponent of a plan, which he described in a 2012 book, to create a wiring diagram of all 100 trillion connections between the neurons of the human brain, an unimaginably vast and complex network known as the connectome.
With connectome mapping, Seung explained last month, it is possible to start answering questions that theorists have puzzled over for decades, including the ones that prompted him to put aside his own work in frustration. He is planning, among other things, to prove that he can find a specific memory in the brain of a mouse and show how neural connections sustain it. “I am going back to settle old scores,” he said.
The question is not whether a map can be made, but what insights it will bring. Will future generations cherish a cartographer’s work or shake their heads and deliver it up to the inclemencies?
The ur-map of this big science is the one produced by the Human Genome Project, a stem-to-stern accounting of the DNA that provides every cell’s genetic instructions. The genome project was completed faster than anyone expected, thanks to Moore’s Law, and has become an essential scientific tool. In its wake have come a proliferation of projects in the same vein — the proteome (proteins), the foldome (folding of proteins) — each promising a complete description of something or other. (One online listing includes the antiome: “The totality of people who object to the propagation of omes.”)
The Brain Initiative, the United States government’s 12-year, $4.5 billion brain-mapping effort, is a conscious echo of the genome project, but neuroscientists find themselves in a far more tenuous position at the outset. The brain might be mapped in a host of ways, and the initiative is pursuing many at once. In fact, Seung and his colleagues, who are receiving some of the funding, are working at the margins of contemporary neuroscience. Much of the field’s most exciting new technology has sought to track the brain’s activity — like functional M.R.I., with its images of parts of the brain “lighting up” — while the connectome would map the brain’s physical structure.
What makes the connectome’s relationship to our identity so difficult to understand, Seung told me, is that we associate our “self” with motion.
a cross-disciplinary group of researchers, including Seung, hit on a new way of thinking that is described as connectionism.
The basic idea (which borrows from computer science) is that simple units, connected in the right way, can give rise to surprising abilities (memory, recognition, reasoning). In computer chips, transistors and other basic electronic components are wired together to make powerful processors. In the brain, neurons are wired together — and rewired.
Every time a girl sees her dog (wagging tail, chocolate brown fur), a certain set of neurons fire; this churn of activity is like Seung’s Colorado River. When these neurons fire together, the connections between them grow stronger, forming a memory — a part of Seung’s riverbed, the connectome that shapes thought.
A typical human neuron has thousands of connections; a neuron can be as narrow as one ten-thousandth of a millimeter and yet stretch from one side of the head to the other. Only once have scientists ever managed to map the complete wiring diagram of an animal — a transparent worm called C. elegans, one millimeter long with just 302 neurons — and the work required a stunning display of resolve. Beginning in 1970 and led by the South African Nobel laureate Sydney Brenner, it involved painstakingly slicing the worm into thousands of sections, each one-thousandth the width of a human hair, to be photographed under an electron microscope.
That was the easy part. To pull a wiring diagram from the stack of images required identifying each neuron and then following it through the sections, a task akin to tracing the full length of every strand of pasta in a bowl of spaghetti and meatballs, using pens and thousands of blurry black-and-white photos. For C. elegans, this process alone consumed more than a dozen years. When Seung started, he estimated that it would take a single tracer roughly a million years to finish a cubic millimeter of human cortex — meaning that tracing an entire human brain would consume roughly one trillion years of labor. He would need a little help.
In 2012, Seung started EyeWire, an online game that challenges the public to trace neuronal wiring — now using computers, not pens — in the retina of a mouse’s eye. Seung’s artificial-intelligence algorithms process the raw images, then players earn points as they mark, paint-by-numbers style, the branches of a neuron through a three-dimensional cube. The game has attracted 165,000 players in 164 countries. In effect, Seung is employing artificial intelligence as a force multiplier for a global, all-volunteer army that has included Lorinda, a Missouri grandmother who also paints watercolors, and Iliyan (a.k.a. @crazyman4865), a high-school student in Bulgaria who once played for nearly 24 hours straight. Computers do what they can and then leave the rest to what remains the most potent pattern-recognition technology ever discovered: the human brain.
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