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                                                                                SPECIAL ISSUE: MILLENNIUM -- BEYOND THE YEAR 2000 

THE NEXT 1,000 YEARS, Page 81

The Frontier Within


By plumbing the deep secrets of the human mind, scientists will
open the way to cures, wonders -- and voyeurism

BY J. MADELEINE NASH


    Contemplate for a moment a tangle of seaweed tossed up on
the shore. This is what a neuron looks like, surrounded by a
thicket of tiny tendrils that serve as communications channels.
Now multiply that neuron 100 billion times. Crammed into the
skull of every human individual are as many neurons as there
are stars in the Milky Way. Each one of these receives input
from about 10,000 other neurons in the brain and sends messages
to a thousand more. The combinatorial possibilities are
staggering. The cerebral cortex alone boasts 1 million billion
connections, a number so large, marvels neuroscientist Gerald
Edelman in his recent book about the brain, Bright Air,
Brilliant Fire, that "if you were to count them, one connection
per second, you would finish counting some 32 million years
after you began."

    Assembled by nature and honed by evolution, the convoluted
3-lb. organ positioned between our ears represents a triumph of
bioengineering, one that continues to elude comprehension and
defy imitation. "The brain," declares molecular biologist James
Watson, co-discoverer of the physical structure of DNA, "is the
most complex thing we have yet discovered in our universe." The
quest to understand the biology of intelligence is likely to
occupy the minds of the world's best scientists for centuries to
come. The task may prove more challenging than those alive today
suppose, requiring perhaps new breakthroughs in physics and
chemistry. Meanwhile, the knowledge spawned by this search
promises to transform society. Here is what lies ahead:


    COMPUTERS WILL EMULATE THE BRAIN BUT NOT REPLACE IT

    From the wheeled cart to the printing press, from the
telephone to the airplane, inventions have enormously expanded
the repertoire of human capabilities, and this trend will
continue, even accelerate. In this century computers have
provided instant access to awesome number-crunching power and a
vast storehouse of information. In coming centuries they will
augment and amplify human skills in far more astounding ways.
Thus, while the brain will not undergo much in the way of
biological evolution, humans, assisted by ever more powerful
computers, will become capable of far greater intellectual
feats. "We won't recognize any difference in brains
themselves," emphasizes Maxwell Cowan, chief scientific officer
of the Howard Hughes Medical Institute in Bethesda, Maryland.
"But we will recognize enormous differences in what brains know
and understand."

    Intriguingly, the brain's expanding knowledge of itself has
begun to suggest radical new approaches to computer design. Like
the brain, the computers of the future will not execute tasks
in serial lockstep but will be capable of doing a million things
in parallel. The chips of which they are composed may well be
silicon, but they will mimic biological systems in almost every
other way. A tantalizing hint of what the future holds comes
from a type of computer known as a neural network. Employing the
time-tested tactic of trial and error, these assemblages of
artificial neurons have already "learned" to recognize scribbled
handwriting, deduce principles of grammar and even mimic the
acoustic sensitivity of the barn owl. By cobbling several of
these sensory systems together, scientists will certainly be
able to create, say, a robot that combines a barn owl's hearing
with the ability to track moving objects and issue an
ear-piercing hoot. Home gardeners may well employ an artificial
owl to chase away rabbits and deer, but they will hardly
consider it an intellectual equal. "Let me put it this way,"
laughs Caltech physicist Carver Mead, a legendary designer of
computer chips. "Two hundred years from now, I will not be
having this conversation with a piece of silicon."


    THE DEAF WILL HEAR, THE BLIND SEE, THE LAME WALK

    By the end of the next century, if not before, scientific
insight into the perceptual centers of the human brain should
vanquish these ancient afflictions. Already scientists have
developed a cochlear implant that bypasses nonfunctioning hair
cells in the ear and stimulates the nerve leading to the
auditory cortex of the brain. Says Michael Merzenich, a
neurophysiologist at the University of California, San
Francisco: "We know that these inputs to the brain are
distorted, yet the patients who have worn them for a while
insist that what they hear sounds perfectly normal." What
appears to occur, says Merzenich, is that the brain somehow
manages to adjust its connections to make sense of the
distortions it receives. This clear demonstration of the
plasticity inherent in the adult brain lends hope that
scientists of the future will succeed in performing other
similar feats. One of these might well be the ability to equip
artificial limbs with electronic "neurons" that can respond to
signals relayed by the brain. These circuits might even include
the equivalents of the axons and dendrites that link one neuron
to another.

    Almost certainly, scientists will master techniques for
stimulating injured neurons to regenerate themselves. The
brains and spinal columns of adult mammals do not possess this
ability, at least not yet. A clue that this should be possible
comes from frogs and salamanders, whose central nervous systems
miraculously regrow following injury. Scientists have
discovered several proteins that may eventually be deployed to
rejuvenate broken spinal cords and damaged optic nerves. "I
don't hold out too much hope for bionic man," says Michael
Stryker, a colleague of Merzenich's who specializes in vision.
"I think we will get there faster using biological techniques."


    GENETIC ENGINEERING WILL EXTEND TO MENTAL TRAITS

    Scientists are currently absorbed in tracking down genes
believed to be responsible for such mental illnesses as manic
depression and schizophrenia. Eventually, they can be expected
to broaden their goals and seek out the genetic tool kit for
building such intellectual traits as musical talent,
mathematical genius and, above all, personality. Shyness, for
instance, appears to have a genetic basis; assertiveness and
hair-trigger anger probably do as well. Like it or not,
predicts Dr. Lewis Judd, chairman of the psychiatry department
at the University of California at San Diego, "We are going to
find that the attitudes we take, the choices we make, are far
more influenced by heredity than we ever thought."

    For the next century or two, if not beyond, schemes for
improving the brain through genetic tinkering are likely to be
confounded by a combination of social taboos, legal
restrictions and sheer biological ignorance. But when the genes
that underlie personality and behavior are isolated and
understood, society will reach a critical ethical divide. A
Pandora's box of options that were not available in centuries
past will suddenly pop wide open. Should would-be parents who
learn a fetus has inherited a strong likelihood of developing
a serious but treatable mental illness opt for an abortion?
Should they choose gene therapy to replace the defective DNA in
their newborn child's brain cells? And while they're
contemplating all this, might they not also consider conferring
on their offspring desirable traits like intelligence?


    MIND READING WILL BE MORE THAN A PARLOR GAME

    The machines that make images of the brain today are large,
expensive contraptions that only major medical centers can
afford. But just as computers have become ever smaller, cheaper
and more powerful, so will the ultrafast successors to
present-day positron-emission tomography and magnetic-resonance
imaging scanners. Washington University neurologist Marcus
Raichle predicts, in fact, that the "brain scopes" of the
future will make a big splash at Disneyland and other theme
parks. One can imagine lines of vacationers waiting to have
their thoughts and emotions imaged in garish hues.

    But these machines will also be put to serious purpose.
Consider, for example, the tantalizing evidence that certain
patterns of brain activity correlate with higher achievement
levels. Competing educational strategies might someday be
judged by whether they stimulate specific areas of the brain and
how strongly. "Is phonics really the best way to teach
reading?" muses Dr. Raichle. "Or is it just another silly idea?
By looking at the brain, I think we'll discover the answer to
that question." And to others as well. Many mothers-to-be have
wondered whether playing music and reciting poetry can
influence embryonic brain development in desirable ways. Someday
they may be able to judge for themselves.

    More important, tomorrow's brain scanners will be able to
assess intellectual strengths and weaknesses in preschool
children. A wide spectrum of mental weaknesses will become
targets for early intervention. Dyslexia could be diagnosed in
infancy, the time when brain plasticity is highest. Therapies
could then be monitored by charting changes in neuronal firing
patterns.


    BRAINS WILL BE HEALTHIER, HAPPIER

    Prominent mainstays of the pharmacopoeia of the future will
be compounds that prevent nerve cells from dying. Much of the
devastation caused by stroke is believed to occur because the
directly injured neurons release massive quantities of the
neurotransmitter glutamate. Normally, tiny bursts of glutamate
act as signals between one neuron and another, triggering the
brief opening of minuscule channels that allow calcium to pass
through the cell's protective membrane. Too much glutamate,
however, causes the channels to remain open too long,
permitting an abnormal, and lethal, influx of calcium. Soon
drugs that mop up excess glutamate or block its action may make
this sort of stroke-related brain damage as preventable as
tissue damage from gangrene. Similar strategies should likewise
succeed in protecting neurons from the ravages of Alzheimer's
disease.

    Needless to say, expanding knowledge of the brain's complex
biochemistry and how it goes awry will bring about more
effective treatments for depression and schizophrenia, panic
attacks and obsessive compulsions, alcoholism and drug
addiction. Along the way, scientists will gain profound
insights into the biochemical signals that create the astounding
range of human emotions. "Which peptides make you sad, which
ones make you happy, and which ones make you feel just grand?"
wonders Columbia University neuroscientist Eric Kandel. That
knowledge could conceivably translate into an ability to
fine-tune those states at will -- through either pharmacology
or sophisticated biofeedback techniques.

    Certainly nothing in the past 100,000 years of cultural
evolution can prepare future generations for the moment when
science lays bare, as it most certainly will, the secrets of
the human mind. "We will be rendered naked," predicts Tufts
University philosophy professor Daniel Dennett, "in a way that
we've never been naked before. The mind boggles at the
varieties of voyeurism, eavesdropping and intrusion that will
become possible." Concepts like good and evil, free will and
individual responsibility, will presumably survive the upheaval,
but not before being shaken to their deepest foundations.
Imagine, for a moment, that a psychiatrist could peer into the
psyche of a serial killer. Could the doctor see what was wrong?
If he could, would he know how to fix it?

    The great adventure on which modern neuroscience has
embarked will end up challenging our most cherished concepts of
who we are. "In the end, we will even figure out how this
tissue in our skulls produces the states of self-awareness we
refer to as consciousness," ventures John Searle, a philosopher
of science at the University of California, Berkeley. But just
as understanding the Big Bang has not permitted humans to
create new universes at will, understanding consciousness will
probably not allow us to construct an artificial brain. Besides,
says University of Iowa neurologist Dr. Antonio Damasio, "a
brain is not likely to work without a body." At the very least,
a disembodied brain would be extremely disoriented and terribly
unhappy.

    In the coming centuries, one imagines, the desire to create
monstrous caricatures of ourselves will dissipate. At long last,
we will reclaim the awe and wonder our predecessors reserved for
machines and turn them back toward our biological selves. Like
Narcissus, we will behold the image of our minds and lose
ourselves in endless admiration.