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Presenting the leading edge in science: Decoding the brain, stringing together the universe and arresting human aging.
Nov 10, 2005 | 
Decoding the brain
The neural code is the most important scientific problem you have (probably) never heard of.
Analogous to the software of a computer, the neural code is the set of rules or the syntax that transforms the electrical pulses emitted by brain cells into perceptions, memories and decisions. 
Knowledge of the neural code could 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 lump of jelly in our skulls generates a unique self with a sense of personal identity and autonomy, a self that perceives, emotes, remembers, imagines, chooses, acts, creates.
Until recently, a complete decoding of the brain seemed impossibly remote, because researchers had limited means of probing the microcircuitry 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 baseball stadium and listening to the roar of the crowd. But over the past decade researchers have begun crafting arrays of microelectrodes that can eavesdrop on hundreds and even thousands of separate neurons simultaneously. These advances "have really transformed the field," says Terry Sejnowski, of the University of California at San Diego, a leading neural-code theorist.
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 enable the paralyzed to control computers and other devices. The Pentagon, which funds research on neural prostheses, has openly broached the possibility of implanting chips in healthy soldiers to enhance their perceptions and memories.
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 those schemes and more. These disputes have led some theorists to warn that the neural code may never be fully deciphered. But 60 years ago, many 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, which has culminated in the Human Genome Project, has been widely acclaimed -- and with good reason, because knowledge of our genetic makeup could enable us to reshape our fundamental nature. A solution to the neural code could, in principle, give us much greater and more direct control over ourselves than mere genetic manipulation. It is not too soon to start pondering the potential consequences of this achievement, especially given the Pentagon's interest. How will knowledge of the neural code be used, and by whom? Who will be liberated, and who enslaved?
Physics: New dimensions
Albert Einstein once said that his chief mission as a scientist was to determine whether God had any choice in creating the universe. In other words, was our cosmos in some sense probable or even inevitable, or is it just an arbitrary, brute fact that we must accept and can never explain? Modern physicists share Einstein's obsession with this riddle. They have constructed an extraordinarily detailed account of physical reality, embodied in the standard model of particle physics, which accounts for electromagnetism and the nuclear forces; and general relativity, Einstein's description of gravity. But physicists still have no idea why we find ourselves in this particular universe ruled by these particular laws.
Physicists such as Lisa Randall, of Harvard, hope to solve the conundrum by finding a theory that combines the standard model and general relativity -- which offer disparate mathematical and conceptual approaches to reality, one quantum mechanical and probabilistic and the other deterministic -- into a single, tidy, consistent package. Randall is a leading proponent of string theory, which for some 20 years now has been the leading candidate for this so-called unified theory. String theory holds that reality boils down to infinitessimal strings, or loops, or membranes vibrating in a hyperspace of 10 or more dimensions. Viewing reality from higher dimensions makes certain problems that have stymied unification efforts much more mathematically tractable.
String theory has suffered from various problems. One is that it offers few predictions that can be tested by any current accelerators. Moreover, far from making our cosmos seem less arbitrary, string theory allows for more than a googol (1 followed by 100 zeros) possible universes with dimensions, particles, forces and other properties radically unlike our own. But Randall has proposed a version of string theory that she believes may solve these problems. In most versions, the extra dimensions are "compactified," wrapped up into balls so small that they cannot be detected. In Randall's variant, which she describes in her acclaimed new book "Warped Passages," some extra dimensions -- or passages, as she calls them -- stretch to infinity and may be experimentally discernible.
Together with Andreas Karch, of the University of Washington, Randall has also shown that a universe like ours emerges quite naturally from the physics she postulates, whereas in other universes gravity would be too stringy or too weak to allow for the emergence of stars, planets and life. Randall hopes that the Large Hadron Collider, a powerful accelerator being built in Switzerland, may provide evidence for her theory within the next decade.
Then we may discover that God had little choice after all.
