All it took was a few jolts of electricity to turn ordinary rats into roborats and for pundits to leap to the conclusion that ordinary humans will soon be transformed into robohumans. Scientists at the State University of New York Downstate Medical Center in Brooklyn sparked a media frenzy two years ago when they demonstrated that rats with electrodes implanted in their brains could be steered like remote-controlled toy cars through an obstacle course. Using a laptop equipped with a wireless transmitter, a researcher stimulated cortical cells governing whisker sensations and reinforced those signals by zapping the rats' pleasure centers. Presto! With this simple setup, the team had created living robots.
Publications around the world proclaimed the imminence of those familiar science-fiction staples, surgically implanted devices that electronically monitor and manipulate our minds. The Economist warned that neurotechnology may be on the verge of "overturning the essential nature of humanity," and New York Times columnist William Safire brooded that neural implants might allow a "controlling organization" to hack into our brains. In a more positive vein, MIT's artificial-intelligence maven Rodney Brooks predicted in Technology Review that by 2020 implants will let us carry out "thought-activated Google searches."
Hollywood's remake of The Manchurian Candidate raises the specter of a remote- controlled soldier turned politician. In fact, officials at the Defense Advanced Research Projects Agency, which funds the roborat team, have suggested that cyborg soldiers could control weapons systems—or be controlled—via brain chips. "Implanting electrodes into healthy people is not something we're going to do anytime soon," says Alan Rudolf, the former head of the DARPA brain-machine research program. "But 20 years ago, no one thought we'd put a laser in the eye. This agency leaves the door open to what's possible."
Of course, that begs the question: Just how realistic are these futuristic scenarios? To achieve truly precise mind reading and control, neuroscientists must master the syntax or set of rules that transform electrochemical pulses coursing through the brain into perceptions, memories, emotions, and decisions. Deciphering this so-called neural code—think of it as the brain's software—is the ultimate goal of many scientists tinkering with brain-machine interfaces. "If you're a real neuroscientist, that's the game you want to play," says John Chapin, a coleader of the roborat research team.
Chapin ranks the neural code right up there with two other great scientific mysteries: the origin of the universe and of life on Earth. The neural code is arguably the most consequential of the three. The solution could, in principle, vastly expand our power to treat ailing brains and to augment healthy ones. It could allow us to program computers with human capabilities, helping them become more clever than HAL in 2001: A Space Odyssey and C-3PO in Star Wars. The neural code could also represent the key to the deepest of all philosophical conundrums—the mind-body problem. We would finally understand how this wrinkled lump of jelly in our skulls generates a unique, conscious self with a sense of personal identity and autonomy.
In addition to being the most significant mystery in science, the neural code may also be the hardest to solve. Despite all they have learned in the past century, neuroscientists have made little headway figuring out exactly how brain cells process information. "It's a bit like saying after a hundred years of researching the body, 'Do you know if testes produce urine or sperm?'" says neuroscientist V. S. Ramachandran of the University of California at San Diego. "Our notions are still very primitive."
The neural code is often likened to the machine code that underpins the operating system of a digital computer. Like transistors, neurons serve as switches, or logic gates, absorbing and emitting electrochemical pulses, called action potentials, which resemble the basic units of information in digital computers. But the brain's complexity dwarfs that of any existing computer. A typical brain contains 100 billion cells—almost as numerous as the stars in the Milky Way galaxy. And each cell is linked via synapses to as many as 100,000 others. The synapses between cells are awash in hormones and neurotransmitters that modulate the transmission of signals, and the synapses constantly form and dissolve, weaken and strengthen in response to new experiences.
Assuming that each synapse processes one action potential per second and that these transactions represent the brain's computational output, then the brain performs at least one quadrillion operations per second, almost a thousand times more than the best supercomputers. Many more computations may occur at scales below or above that of individual synapses, says Steven Rose, a neurobiologist at the Open University in England. "The brain may use every possible means of carrying information."
Optimists recall that in the middle of the last century, some biologists feared that the genetic code was too complex to crack. Then in 1953 Francis Crick and James Watson unraveled the structure of DNA, and researchers quickly established that the double helix mediates an astonishingly simple genetic code governing the heredity of all organisms. The neural code is not likely to reveal such an elegant, universal solution. The brain is "so adaptive, so dynamic, changing so frequently from instant to instant," says Miguel Nicolelis, a neural-prosthesis researcher at Duke University, that "it may not be proper to use the term 'code.' "
Nicolelis has faith that science will one day ferret out all the brain's information-processing tricks—or at least enough of them to yield huge improvements in neural prostheses for people who are paralyzed, blind, or otherwise disabled. Yet he believes that certain aspects of our minds may remain inviolable because our most meaningful thoughts and memories are written in a code, or language, that is unique to each of us. "There will always be some mystery," Nicolelis says.
If so, the bad news is that brain chips will never be sophisticated enough for us to learn new languages instantly or have a "mental telephone" conversation with a friend "simply by thinking about talking," as Popular Science has prophesied. The good news is that we are not on the verge of what The Boston Globe has called a "Matrix-like cyberpunk dystopia" in which we all become robohumans, controlled by implants that "impose false memories" and "scan for wayward thoughts."
All the loose speculation provoked by roborats is ironic considering that the experiment is just a small-scale replay of a major media event that is 40 years old. In 1964, José Delgado, a neuroscientist from Yale University, stood in a Spanish bullring as a bull with a radio-equipped array of electrodes, or "stimoceiver," implanted in its brain charged toward him. When Delgado pushed a button on a radio transmitter he was holding, the bull stopped in its tracks. Delgado pushed another button, and the bull obediently turned to the right and trotted away. The New York Times hailed the event as "probably the most spectacular demonstration ever performed of the deliberate modification of animal behavior through external control of the brain."
Delgado also conducted stimoceiver experiments in cats, monkeys, chimpanzees, and even human psychiatric patients. He showed that he could jerk the limbs of patients like marionettes, as well as induce sensations such as euphoria, sexual arousal, sleepiness, garrulousness, terror, and rage. In his 1969 book Physical Control of the Mind: Toward a Psychocivilized Society, Delgado extolled the promise of brain stimulation techniques for curbing violent aggression and other maladaptive traits.
Delgado's work—partly funded by the Pentagon—provoked fears of government plots to transform citizens into robots. He dismissed this "Orwellian possibility," pointing out that the technology was still much too unreliable and crude for precise mind control. The major impediment to progress, he wrote, is that "our present knowledge regarding the coding of information . . . is so elemental." Now 89 and living in San Diego, Delgado still follows advances in brain-machine interfaces. The potential of brain-stimulation "has not been fully developed," he says, because the neural code remains "very difficult to untangle."