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After the Double Helix: Unraveling the Mysteries of the State of Being
April 13, 2004
By MARGARET WERTHEIM
SAN DIEGO - Sitting at lunch on the patio of his home here
one muggy day last June, Francis Crick was expounding on
the mind-body problem and the thorny subject of the human
"self."
Where is the line between mind and matter? he asked. Aside
from the neurons in our brains, the human body contains
tens of millions of neurons in the enteric nervous system,
which extends into the stomach and intestines. "When you
digest your lunch is that you?" Dr. Crick asked.
Body and mind are the twin problems around which Dr.
Crick's life has spiraled, much like the double helix
structure of DNA that he and Dr. James D. Watson are famous
for discovering half a century ago. Though his research on
"the molecule of life" is what he is best known for, in his
28 years at the Salk Institute for Biological Studies, his
work has focused on the mind, and in particular the
question of consciousness.
Until recently, that subject was viewed with deep suspicion
in scientific circles, but Dr. Crick has led a campaign to
make it acceptable. These days it is even fashionable.
While some philosophers claim that consciousness is a
phenomenon outside the purview of material science, Dr.
Crick dismisses such arguments with the imperious
confidence that is part of his legend. "The mechanism is
the important part; the rest is just playing with words,"
he said in a recent interview.
Dr. Crick's career has been characterized by celebrated
collaborations, and for the past decade he has been working
with Dr. Christof Koch, a professor of computation and
neural systems at the California Institute of Technology.
Together they have developed a framework, which Dr. Koch
has spelled out in his new book, "The Quest for
Consciousness: A Neurobiological Approach."
In late March, Dr. Crick and Dr. Koch sat down in San Diego
to discuss their recent work. Now 87 and suffering from the
advanced stages of cancer, Dr. Crick has been put on a new
regime of chemotherapy. Yet in spite of the toxic cocktail,
he seems as sharp as ever, tossing out answers like
perfectly aimed darts.
Almost from the start of his career, he was obsessed with
two problems: "the borderline between the living and the
nonliving and the nature of consciousness." In the late
1940's, after a notable career as a physicist in the
British Admiralty, he began to investigate the first topic
by studying the structure of proteins.
In 1951, he teamed up with Dr. Watson to determine the
structure of DNA. Few scientists believed DNA carried the
genetic code, but Mr. Crick - he did not get his doctorate
until 1954 - and Dr. Watson were convinced that it did.
Their epoch-making paper on the double helix was published
in 1953, and in 1962 they won the Nobel Prize in Physiology
or Medicine, with their colleague Dr. Maurice Wilkins.
Dr. Crick next collaborated with Dr. Sydney Brenner, and
together they worked on the problem of how the genetic code
translated into proteins that build organisms. By the end
of the 60's, the foundations of molecular biology were well
understood, and Dr. Crick was eager to go to his next great
question. In 1976, he moved to the Salk Institute,
reinventing himself as a neuroscientist.
Since then, Dr. Crick has been a tireless champion of the
brain. In a 1979 editorial in Scientific American, he
argued that the time had come for science to take on the
previously forbidden subject of consciousness. In his 1994
book "The Astonishing Hypothesis: The Scientific Search for
the Soul," he went further. "You," he wrote, "your joys and
your sorrows, your memories and your ambitions, your sense
of personal identity and free will, are in fact no more
than the behavior of a vast assembly of nerve cells and
their associated molecules." He outlined an empirical
approach focusing on visual consciousness.
His ideas have formed the inspiration for Dr. Koch's
research at Caltech: the goal is to find "the neural
correlates of consciousness," or N.C.C.'s - the neuronal
states and processes associated with conscious awareness.
Dr. Koch and his graduate students are finally gaining
experimental evidence for what Dr. Crick had termed the
"awareness neurons" that enable us to see.
Dr. Crick's ideas, along with those of another Nobelist,
Dr. Gerald M. Edelman, helped shift the direction of
neuroscience. These days, papers on the neural correlates
of consciousness are increasingly commonplace, though Dr.
Nancy Kanwisher, a neuroscientist at the Massachusetts
Institute of Technology, noted that still "very few
neuroscientists directly discuss the N.C.C.'s."
But even Dr. David Chalmers, a philosopher at the
University of Arizona and a leading critic of the
materialist approach to mind, acknowledges the value of the
work of Dr. Crick and Dr. Koch. "Everyone agrees now that
there are systematic processes happening in the brain that
must correlate with awareness," he said.
Many of Dr. Koch's experiments are aimed at teasing out
what the brain is registering beneath the radar of
conscious awareness. One tool for studying this is trace
conditioning. Using it, a subject is presented with two
consecutive stimuli - say an image and a mild electric
shock - separated by a delay. After a period of training,
subjects begin to anticipate the shock (measured by a rise
in skin conductance on their palms) when they see the
image.
Using M.R.I., Dr. Koch's team has shown that in trace
conditioning, an area of the brain known as the anterior
cingulate cortex is activated. They have found that when
they remove this area from mice, the creatures cannot be
trace conditioned, causing Dr Koch to speculate that this
area of the brain is critical for consciousness.
Dr. Koch notes that the advent of M.R.I. has also made it
possible to see which parts of the brain are active during
a "percept" - as when someone sees a face. Dr. Kanwisher
has shown that there are specific parts of the brain that
register awareness of faces and objects.
A small group of patients with epilepsy are letting
scientists get an even more intimate look at the brain.
Working with Dr. Itzhak Fried, a neurosurgeon at the
University of California, Los Angeles, graduate students of
Dr. Koch's are exposing the patients to images and checking
the activity of individual neurons as recorded by
electrodes implanted in their brains.
Dr. Koch's team is looking for neuronal evidence of "change
blindness" in these patients. An array of four photographs
is flashed on a screen, followed about a second later by
another array in which one of the images has changed. "It
can be surprisingly difficult to consciously see such
changes," Dr. Koch said, though evidence suggests that
neurons may be registering them.
Not everyone is convinced that understanding the neural
correlates will explain awareness. "There is a difference
between correlation and explanation," Dr. Chalmers said.
"The question is, once we have these neural correlates,
What do we do with them? I don't think the N.C.C.'s is a
final theory."
In tackling consciousness, Dr. Crick and Dr. Koch have
reframed the central question. Traditionally the problem
has been cast in terms of subjectivity. How is it, for
example, that when someone sees red (which physically
speaking is electromagnetic waves of a particular
frequency) there is also a subjective feeling of redness?
The "redness" of red and the "painfulness" of pain are what
philosophers refer to as qualia. The gap between the
objectivity of material science (the electromagnetic waves)
and the subjectivity of human experience (the qualia) has
led some philosophers to conclude that this chasm cannot be
bridged by any materialist explanation.
Rather than getting bogged down in the depthless ooze of
qualia, Dr. Crick and Dr. Koch sidestep the issue. Instead
of asking the philosophical question of what consciousness
is, they have restricted themselves to trying to understand
what is going on at the neurological level when
consciousness is present.
While many scientists assume that consciousness is a global
property of the brain - "a gestalt phenomenon" - Dr. Koch
and Dr. Crick say they believe that only a few neurons are
responsible at any given moment. Of the 50 billion or so
neurons in the brain, Dr. Crick says that perhaps only tens
of thousands, or even a few thousand, give rise to the
feeling of conscious awareness. "We believe it is
essentially a local phenomenon," he said.
That position is certainly contentious. "The idea that
there is a special population of neurons that mediate
awareness is a minority view," Dr. Kanwisher noted.
Dr. Crick says he is convinced that the origin of
consciousness is a solvable problem, albeit complex.
He drew an analogy with another phenomenon once attributed
to transcendent powers: "People think the brain is
mysterious but not the weather. Why is that?" In some ways,
he suggested, the brain may be less enigmatic than the
weather, because "we don't yet have a clear understanding
of how raindrops form but we do know how individual neurons
and synapses work."
The elucidation of the double helix ushered in the age of
molecular genetics, which has now given rise to the vast
applications of genetic engineering. Elucidating
consciousness could have similarly portentous results, Dr.
Koch suggests.
One potential application, he says, is some kind of
instrument for measuring its intensity, perhaps a
"consciousometer." Anesthesiologists might use it to
determine when a patient under sedation is truly out. But
in his book, Dr. Koch also raises the possibility of more
troubling uses, including measuring the awareness levels of
severely retarded children and elderly patients with
dementia.
Or, he asks, "How do we know that a newborn baby is
conscious?" Perhaps consciousness is something that doesn't
begin at birth, he said, but gradually emerges.
"This research is going to pose enormous legal and ethical
questions," Dr. Koch acknowledged in the recent interview.
"I'm not convinced that people want to know how
consciousness works," he said. "They feel cast out of the
world of meaning."
Having solved one of the basic mysteries of life here on
Earth, Dr. Crick seems happy to skewer any notions of a
life beyond. For him, the most profound implication of an
operational understanding of consciousness is that "it will
lead to the death of the soul."
"The view of ourselves as `persons' is just as erroneous as
the view that the Sun goes around the Earth," he said. He
predicted that "this sort of language will disappear in a
few hundred years."
"In the fullness of time," he continued, "educated people
will believe there is no soul independent of the body, and
hence no life after death."
http://www.nytimes.com/2004/04/13/science/13CRIC.html?ex=1082996114&ei=1&en=4fc339cb20b7ac14
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