Cracking the Neural Code, Science’s Biggest Mystery

Chances are you have never heard of the neural code. And yet from both a practical and purely intellectual perspective, the neural code is the most important remaining scientific mystery.

Analogous to the machine code of a digital computer, the neural code is the software, set of rules or syntax that transforms physiological processes in the brain into a mind. A solution to the neural code could—in principle--give us almost unlimited power over our psyches, because we could monitor and manipulate brain cells with exquisite precision by speaking to them in their own private language.

The neural code could also solve one of philosophy’s oldest conundrums, the mind-body problem. We may finally understand how this wrinkled, three-pound lump of jelly in our skulls generates a unique self perceives, emotes, remembers, imagines, chooses, acts and creates.

The neural code is such a dauntingly complex, technical topic--overlapping with nonlinear dynamics, information theory and other esoteric fields—that it receives little publicity beyond specialized journals. Moreover, until recently a complete decoding of the brain seemed impossibly remote, because researchers had limited means of probing the micro-circuitry of living brains. Trying to glean the neural code with external scanning methods such as magnetic-resonance imaging or electroencephalography is like trying to learn English by standing outside a soccer stadium and listening to the roar of the crowd.

Over the past decade or two, however, researchers have begun crafting arrays of microelectrodes that can eavesdrop on hundreds and even thousands of separate neurons simultaneously. Scientists have also acquired ever-more-powerful computers and algorithms for analyzing data.

The immediate goal of many researchers is producing “neural prostheses” for the disabled. By far the most successful neural prosthesis is the artificial cochlea, which restores hearing by feeding signals from an external microphone to an implanted chip that stimulates the auditory nerve. Work is proceeding slowly but surely on prostheses that can restore vision to the blind and allow the paralyzed to control computers and other devices. The Pentagon, which together with the National Institutes of Health is a major funder of research on neural prostheses, has openly broached the possibility of implanting chips in healthy soldiers to enhance their perceptions and memories.

Beyond these bionic possibilities, neural-code research could have a dramatic impact on artificial intelligence, which has thus far failed to deliver on its promise of creating truly intelligent machines. If the brain’s programming tricks can be transferred to computers and robots, they may finally become as clever as HAL in the film 2001 and C3PO in Star Wars. In the most far-fetchedscenario of all, long envisioned by artificial-intelligence mavens such as Marvin Minsky and Ray Kurzweil, mastery of the neural code might allow us to transform our psyches into software programs--strings of ones and zeros—that can be downloaded into machines. We might then live forever in cyberspace.

Neuroscientists are still far from converging on a solution to the neural code. They are embroiled in debates over whether information is represented primarily by signals from individual neurons, by many neurons firing in lockstep, by even higher-level waves of chaotic electrical activity sweeping through the brain, or all of the schemes above and more.

These disputes have led some theorists to warn that the neural code may never be fully deciphered. But 60 years ago, some biologists feared 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.

Science’s success in deciphering the genetic code has been widely acclaimed—and with good reason, because knowledge of our genetic makeup could allow us to reshape our fundamental nature. A solution to the neural code could, in principle, give us much greater, more direct control over ourselves than genetic manipulation. It is not too soon to start pondering the potential consequences of this achievement. How will knowledge of the neural code by used, and by whom? Who will be liberated, and who enslaved?

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