The Future of the Mind (41 page)

Although Obama’s speech did not give details, scientists quickly filled in many of the gaps. Neurologists pointed out that, on one hand, it is now possible to use delicate instruments to monitor the electrical activity of single neurons. On the other hand, using MRI machines, it is possible to monitor the global behavior of the entire brain. What is missing, they pointed out, is the middle ground, where most of the interesting brain activity takes place. It is in this middle ground, involving the pathways of thousands to millions of neurons, that there are huge gaps in our understanding of mental disease and behavior.

To tackle this enormous problem, scientists laid out a tentative fifteen-year program. In the first five years, neurologists hope to monitor the electrical activity of tens of thousands of neurons. The short-term goals might include reconstructing the electrical activity of important parts of animal brains, such as the medulla of the Drosophila fruit fly or the ganglion cells in a mouse retina (which has fifty thousand neurons).

Within ten years, that number should increase to hundreds of thousands of neurons. This could include imaging the entire Drosophila brain (135,000 neurons) or even the cortex of the Etruscan shrew, the smallest known mammal, with a million neurons.

Finally, within fifteen years, it should be possible to monitor millions of neurons, comparable to the zebrafish brain or the entire neocortex of a mouse. This could pave the way toward imaging parts of the brains of primates.

Meanwhile, in Europe, the Human Brain Project would tackle the problem from a different point of view. Over a ten-year period, it will use supercomputers to simulate the basic functioning of the brains of different
animals, starting with mice and working up to humans. Instead of dealing with individual neurons, the Human Brain Project will use transistors to mimic their behavior, so that there will be computer modules that can act like the neocortex, the thalamus, and other parts of the brain.

In the end, the rivalry between these two gigantic projects could create a windfall by generating new discoveries for treating incurable diseases and spawning new industries. But there is also another, unstated goal. If one can eventually simulate a human brain, does it mean that the brain can become immortal? Does it mean that consciousness can now exist outside the body? Some of the thorniest theological and metaphysical questions are raised by these ambitious projects.

BUILDING A BRAIN

Like many other children, I used to love taking apart clocks, disassembling them, screw for screw, and then trying to see how the whole thing fit together. I would trace each part mentally, seeing how one gear connected to the next one, until the whole thing fit together. I realized the mainspring turned the main gear, which then fed a sequence of smaller gears, which eventually turned the hands of the clock.

Today, on a much larger scale, computer scientists and neurologists are trying to take apart an infinitely more complex object, the most sophisticated object we know about in the universe: the human brain. Moreover, they wish to reassemble it, neuron by neuron.

Because of rapid advances in automation, robotics, nanotechnology, and neuroscience, reverse engineering the human brain is no longer idle speculation for polite after-dinner banter. In the United States and Europe, billions of dollars will soon be flowing into projects once considered preposterous. Today a small band of visionary scientists are dedicating their professional lives to a project that they may not live to see completed. Tomorrow their ranks could swell into an entire army, generously funded by the United States and the nations of Europe.

If successful, these scientists could alter the course of human history. Not only might they find new cures and therapies for mental illnesses, they might also unlock the secret of consciousness and perhaps upload it into a computer.

It is a daunting task. The human brain consists of over one hundred billion neurons, approximately as many stars as there are in the Milky Way galaxy. Each neuron, in turn, is connected to perhaps ten thousand other neurons, so altogether there are a total of ten million billion possible connections (and that does not begin to compute the number of pathways there are among this thicket of neurons). The number of “thoughts” that a human brain can conceive of is therefore truly astronomical and beyond human ken.

Yet that has not stopped a small bunch of fiercely dedicated scientists from attempting to reconstruct the brain from scratch. There is an old Chinese proverb, “A journey of a thousand miles begins with the first step.” That first step was actually taken when scientists decoded, neuron for neuron, the nervous system of a nematode worm. This tiny creature, called
C. elegans
, has 302 neurons and 7,000 synapses, all of which have been precisely recorded. A complete blueprint of its nervous system can be found on the Internet. (Even today, it is the only living organism to have its entire neural structure decoded in this way.)

At first, it was thought that the complete reverse engineering of this simple organism would open the door to the human brain. Ironically, the opposite has happened. Although the nematode’s neurons were finite in number, the network is still so complex and sophisticated that it has taken years to understand even simple facts about worm behavior, such as which pathways are responsible for which behaviors. If even the lowly nematode worm could elude our scientific understanding, scientists were forced to appreciate how complex a human brain must be.

THREE APPROACHES TO THE BRAIN

Because the brain is so complex, there are at least three distinct ways in which it can be taken apart, neuron by neuron. The first is to simulate the brain electronically with supercomputers, which is the approach being taken by the Europeans. The second is to map out the neural pathways of living brains, as in BRAIN. (This task, in turn, can be further subdivided, depending on how these neurons are analyzed—either anatomically, neuron by neuron, or by function and activity.) And third, one can decipher the genes that control the development of the brain, which is an approach pioneered by billionaire Paul Allen of Microsoft.

The first approach, simulating the brain using transistors and computers, is forging ahead by reverse engineering the brains of animals in a certain sequence: first a mouse, then a rat, rabbit, and a cat. The Europeans are following the rough trail of evolution, starting with simple brains and working upward. To a computer scientist, the solution is raw computing power—the more, the better. And this means using some of the largest computers on Earth to decipher the brains of mice and men.

Their first target is the brain of a mouse, which is one-thousandth the size of a human brain, containing about one hundred million neurons. The thinking process behind a mouse brain is being analyzed by the IBM Blue Gene computer, located at the Lawrence Livermore National Laboratory in California, where some of the biggest computers in the world are located; they’re used to design hydrogen warheads for the Pentagon. This colossal collection of transistors, chips, and wires contains 147,456 processors with a staggering 150,000 gigabytes of memory. (A typical PC may have one processor and a few gigabytes of memory.)

Progress has been slow but steady. Instead of modeling the entire brain, scientists try to duplicate just the connections between the cortex and the thalamus, where much of brain activity is concentrated. (This means that the sensory connections to the outside world are missing in this simulation.)

In 2006, Dr. Dharmendra Modha of IBM partially simulated the mouse brain in this way with 512 processors. In 2007, his group simulated the rat brain with 2,048 processors. In 2009, the cat brain, with 1.6 billion neurons and nine trillion connections, was simulated with 24,576 processors.

Today, using the full power of the Blue Gene computer, IBM scientists have simulated 4.5 percent of the human brain’s neurons and synapses. To begin a partial simulation of the human brain, one would need 880,000 processors, which might be possible around 2020.

I had a chance to film the Blue Gene computer. To get to the laboratory, I had to go through layers and layers of security, since it is the nation’s premier weapons laboratory, but once you have cleared all the checkpoints, you enter a huge, air-conditioned room housing Blue Gene.

The computer is truly a magnificent piece of hardware. It consists of racks and racks of large black cabinets full of switches and blinking lights, each about eight feet tall and roughly fifteen feet long. As I walked among the cabinets that make up Blue Gene, I wondered what kinds of operations it
was performing. Most likely, it was modeling the interior of a proton, calculating the decay of plutonium triggers, simulating the collision of two black holes, and thinking of a mouse, all at once.

Then I was told that even this supercomputer is giving way to the next generation, the Blue Gene/Q Sequoia, which will take computing to a new level. In June 2012, it set the world’s record for the fastest supercomputer. At peak speed, it can perform operations at 20.1 PFLOPS (or 20.1 trillion floating point operations per second). It covers an area of three thousand square feet, and gobbles up electrical energy at the rate of 7.9 megawatts, enough power to light up a small city.

But with all this massive computational firepower concentrated in one computer, is it enough to rival the human brain?

Unfortunately, no.

These computer simulations try only to duplicate the interactions between the cortex and the thalamus. Huge chunks of the brain are therefore missing. Dr. Modha understands the enormity of his project. His ambitious research has allowed him to estimate what it would take to create a working model of the entire human brain, and not just a portion or a pale version of it, complete with all parts of the neocortex and connections to the senses. He envisions using not just a single Blue Gene computer but thousands of them, which would fill up not just a room but an entire city block. The energy consumption would be so great that you would need a thousand-megawatt nuclear power plant to generate all the electricity. And then, to cool off this monstrous computer so it wouldn’t melt, you would need to divert a river and send it through the computer circuits.

It is remarkable that a gigantic, city-size computer is required to simulate a piece of human tissue that weighs three pounds, fits inside your skull, raises your body temperature by only a few degrees, uses twenty watts of power, and needs only a few hamburgers to keep it going.

BUILDING A BRAIN

But perhaps the most ambitious scientist who has joined this campaign is Dr. Henry Markram of the École Polytechnique Fédérale de Lausanne, in Switzerland. He is the driving force behind the Human Brain Project, which has received over a billion dollars of funding from the European Commission.
He has spent the last seventeen years of his life trying to decode the brain’s neural wiring. He, too, is using the Blue Gene computer to reverse engineer the brain. At present, his Human Brain Project is running up a bill of $140 million from the European Union, and that represents only a fraction of the computer firepower he will need in the coming decade.

Dr. Markram believes that this is no longer a science project but an engineering endeavor, requiring vast sums of money. He says, “To build this—the supercomputers, the software, the research—we need around one billion dollars. This is not expensive when one considers that the global burden of brain disease will exceed twenty percent of the world gross domestic project very soon.” To him, a billion dollars is nothing, just a pittance compared to the hundreds of billions in bills stemming from Alzheimer’s, Parkinson’s, and other related diseases when the baby boomers retire.

So to Dr. Markram, the solution is one of scale. Throw enough money at the project, and the human brain will emerge. Now that he has won the coveted billion-dollar prize from the European Commission, his dream may become a reality.

He has a ready answer when asked what the average taxpayer will get from this billion-dollar investment. There are three reasons, he says, for embarking on this lonely but expensive quest. First, “
It’s essential for us to understand the human brain if we want to get along in society, and I think that it is a key step in evolution. The second reason is, we cannot keep doing animal experimentation forever.… It’s like a Noah’s Ark. It’s like an archive. And the third reason is that there are two billion people on this planet that are affected by mental disorder.…”

To him, it is a scandal that so little is known about mental diseases, which cause so much suffering to millions of people. He says, “
There’s not a single neurological disease today in which anybody knows what is malfunctioning in this circuit—which pathway, which synapse, which neuron, which receptor. This is shocking.”

At first, it may sound impossible to complete this project, with so many neurons and so many connections. It seems like a fool’s errand. But these scientists think they have an ace in the hole.

The human genome consists of roughly twenty-three thousand genes, yet it can somehow create the brain, which consists of one hundred billion neurons. It seems to be a mathematical impossibility to create the human
brain from our genes, yet it happens every time an embryo is conceived. How can so much information be crammed into something so small?

The answer, Dr. Markram believes, is that nature uses shortcuts. The key to his approach is that certain modules of neurons are repeated over and over again once Mother Nature finds a good template. If you look at microscopic slices of the brain, at first you see nothing but a random tangle of neurons. But upon closer examination, patterns of modules that are repeated over and over appear.

(Modules, in fact, are one reason why it is possible to assemble large skyscrapers so rapidly. Once a single module is designed, it is possible to repeat it endlessly on the assembly line. Then you can rapidly stack them on top of one another to create the skyscraper. Once the paperwork is all signed, an apartment building can be assembled using modules in a few months.)