November 23rd, 2003 |
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From http://www.laweekly.com/ink/03/53/features-wertheim.php.
The Zombie Within
Christof Koch and the Science of Consciousness
by Margaret Wertheim
1. EXPERIENCING THE ABSOLUTE
A hundred feet above me, Christof Koch is hanging by a thread. Three quarters
of the way up a rock face, he has lost his grip and is now dangling at the end
of a rope above cascading waves of flesh-colored granite in the spectacular
“Real Hidden Valley” canyon of the Joshua Tree National Monument. As a professor
of computation and neural systems at Caltech, Koch heads a team of researchers
who are trying to discover the physiological basis of consciousness. At the
moment, however, his own consciousness is sorely taxed. “What am I supposed to
do?” he calls to his superbly skilled climbing partner, fellow Caltech
scientist Kai Zinn, who is waiting at the top.
Under Zinn’s guidance, Koch regains his hold on the vertical face and
clambers to the top, disappearing over the edge in a puff of climbing chalk and
a flash of red booties. For a moment, there is nothing but rocks and sky and a
single swallow flitting overhead. Then suddenly the air resounds with a whoop,
echoes ricocheting off the canyon walls as if the very geology were rejoicing in
his triumph.
Koch is a man infectiously in love with life: In addition to rock climbing,
about which he insists he is a novice, his hobbies include swing dancing, at
which he is something of an expert. As a university student in Germany, he
belonged to a fraternity that practiced Mensur Fechten or ritual fencing,
in which opponents stand a foot apart and slice at the air in front of one
another’s faces with razor-sharp swords. In his 20s, Koch took up ballet — “I
loved the women. I loved the music. And I loved the gracefulness of the
movement.” Now, as he watches Zinn defy gravity on an overhanging face, he
reflects that climbing is a lot like ballet, at its best an exquisitely
choreographed, weightless dance. “Experiencing the absolute,” Koch calls it.
At first glance, rock climbing would seem to require maximal conscious
awareness, but as Zinn rappels to the ground Koch tells me that the aim is to
let go of your mind and let the body take over. Great climbers, like great
dancers, must relinquish control to the unconscious mind. No one could
have more respect for the powers of the unconscious than Koch. Most of what we
do, he says, is not under our conscious control; we’re not even aware we’re
doing it. Take walking: “When you walk, you don’t think lift leg, move leg
forward, put leg down. You just walk!” The same is true for talking. When you
speak, you don’t suddenly have to think about grammar and syntax and vocabulary,
you just open your mouth and the words come out. “If you had to consciously
think through that stuff,” says Koch, “you’d never get anywhere.”
So much of our human fluidity results from automatic processes buried deep in
the mind far below perception, what Koch refers to in his forthcoming book,
The Quest for Consciousness, as “an army of unconscious sensory-motor
agents” or “zombie agents.” He insists that for much of our lives we are in
effect zombies. “You drive to work on autopilot, move your eyes, brush your
teeth, tie your shoelaces, talk, and all the other myriad chores that constitute
daily life.” Indeed, he says, “Any sufficiently well-rehearsed activity is best
performed without conscious, deliberate thought. Reflecting too much about any
one action is likely to interfere with its seamless execution.”
Given the range and effectiveness of these zombie agents, Koch believes the
great mystery is why we are not complete zombies. Or to put it another
way: What purpose does consciousness serve? Why does it exist at all?
2. THE DOORS OF PERCEPTION
On the desk in Koch’s office in Caltech’s Beckman Building stands an object
that serves as a reminder of the problems that bedevil brain science, and the
follies to which its practitioners are prone — a small white phrenology bust,
its skull divided by black lines into regions such as “Self-Esteem,” “Ideality”
and “Sublimity.” Behind the desk, dressed in faded jeans and an electric-blue
shirt, Koch is expounding on the current state of consciousness studies. He
speaks at a machine-gun pace, as if there is barely enough time in life to get
through all the ideas that are crowding through his head. It’s a habit that has
infected his entire lab, the byproduct of an intellectual virus that instills in
its host an urgent need to know, and know now, how the mind functions.
For the past 2,500 years, Koch notes, philosophers have been trying to figure
out the relationship between mind and body. “We know that if your heart stops
beating you will not be conscious, but what are the other physiological
requirements for a state of conscious awareness?” Descartes famously believed
the bridge between body and mind was in the pineal gland, but he had no idea how
that connection might operate. And neither does anyone today, Koch says.
Formulated on the foundation of Cartesian dualism, Western science seems on the
subject of human subjectivity to run smack up against a wall of its own
devising. In a recent paper in the journal Nature, Koch and his longtime
collaborator Francis Crick (co-discoverer of the double helix of DNA) stated
bluntly, “The physical basis of consciousness appears to be the most singular
challenge to scientific, reductionist worldview.”
Koch’s interest in the mind dates back to his student days in Germany. There
he majored in both physics and philosophy, the German scientific-education
system being considerably less hostile to the latter discipline than are many of
its American counterparts. Koch’s education actually spanned three continents.
The son of a diplomat, he was born in Kansas City, Missouri — “I’m as American
as apple pie,” he jokes in an accent rippling with Teutonic undercurrent. He
spent his high school years in Morocco, where he graduated with a French
baccalaureate, then went on to Germany and a doctorate in information processing
from the Max Planck Institute for Biological Cybernetics. Before coming to
Caltech, he was based at MIT.
More than a few philosophers have expressed the view that, in principle,
science cannot provide an explanation for the phenomenon of
consciousness. University of Arizona mind-think superstar David Chalmers has
suggested that entirely new kinds of laws might be involved; Oxford physicist
Roger Penrose believes the solution lies in as-yet-undetected quantum processes;
for philosopher Colin McGinn, the problem is simply intractable. Koch is buying
none of this. Under the watchful gaze of his phrenology bust, he insists, “It
behooves us with science not to say that we can’t do this.” Philosophers
can argue forever, he says, but “You can’t solve the problems of mind just by
thinking about them. You have to go out and do experiments and see what is
actually going on.”
Koch’s lab is dedicated to the proposition that the doors of perception can
be subjected to rigorous empirical scrutiny, that the mental state of
consciousness must be accompanied by physiological processes that can be
studied scientifically. His mission in life is to identify what he and Crick
have called these “neurological correlates of consciousness.”
Of the 30 billion neurons in the human brain, most of them are probably
not involved in the feeling of conscious awareness. “At any moment, some
neuronal processes in your head correlate with consciousness, while others do
not — what is the difference between them?” Koch asks. Or as he
puts it more formally in his book, “What are the neuronal mechanisms sufficient
to cause a specific conscious percept” such as seeing the color red, or hearing
a piece of music?
Until recently, there seemed little hope for progress. Now, according to
Koch, neuroscientists finally possess appropriate tools. Functional MRI scanners
are making it possible to examine human brains in situ, while advances in neural
recording are enabling scientists to see the outputs of individual neurons.
Researchers at his lab are collaborating with a neurosurgery team at UCLA to
investigate the response of neurons in people scheduled for brain surgery. In
particular, Koch is interested in the problem of visual consciousness: how and
when and under what circumstances we are consciously aware of what we see.
So much of what we see we are not aware of at all. As we sit in Koch’s
office, he offers to reveal to me a small portion of my own zombie self. For a
moment I am seized by visions of a nasty chemical cocktail, my mind turned to
mush, my body rendered into a helpless puppet, but instead of reaching for a
syringe, Koch turns on his computer. He brings up an image of an airplane on a
runway and tells me that when he presses a key some major feature will
disappear. I am to tell him what it is. Koch jabs at the keyboard and the image
flashes momentarily, but as far as I can tell everything remains the same. He
does it again, several times, but still I see nothing different. Finally Koch
tells me it is the aircraft’s fuselage that disappears. Once it’s pointed out,
the omission becomes glaringly evident.
If our minds don’t notice things that do occur, they can also invent things
that don’t. Koch pulls up another image, a simple black screen speckled with
slow-moving blue dots and a couple dozen bright-yellow spots. He asks me to
stare at the screen and tell him what happens. After about a minute, some of the
yellow spots begin to wink on and off. Wrong, Koch tells me. Nothing happens.
All the spots remain on the screen; my mind has just invented the flashing.
Koch’s lab has a slew of more sophisticated versions of these and other
experiments, which teach us, he says, that what we see “is not a simple mapping
of the world out there, but a construction” that results from complex neural
interactions. In short, I am not a camera but a highly nonlinear
processing system. Koch hopes that if he can tease out the neural correlates of
visual awareness he will be able to cast light on other aspects of conscious
perception — including that greatest of all conundrums, self-consciousness.
3. CONSCIOUSNESS REFRAMED
As long ago as the 1890s, William James dreamed about a scientific
explanation for consciousness. Yet for much of the past century, the C-word was
viewed with nearly as much disdain in scientific circles as the notion of a
soul. Over the last decade, however, consciousness has become one of the hottest
topics in science — a steady stream of books announce the latest theories; two
peer-review journals have been formed (Consciousness and Cognition and
The Journal of Consciousness Studies); and the field has spawned a slew of
conferences, from the strictly academic events of the Society for the Study of
Consciousness to the freewheeling hoopla of the Tucson Conferences, where Koch
is on the program committee. “We get everyone from neurologists to shamanists to
people experimenting with drugs,” he says.
The emergence of consciousness as a respectable scientific topic is in large
part due to the influence of Crick and fellow Nobel Laureate Gerald Edelman. In
1979, in an editorial accompanying a special Scientific American issue on
the brain, Crick suggested that the time had come to move forward on this
hitherto verboten subject. Fifteen years later, in his controversial book The
Astonishing Hypothesis, Crick threw down the gauntlet: “A person’s mental
activities are entirely due to the behavior of nerve cells, glial cells, and the
atoms, ions and molecules that make them up.” What exactly are those behaviors?
Crick advocated focusing on the subproblem of visual consciousness, and he put
forward a research program designed to pinpoint the “awareness neurons” that
enable us to see. His ideas have formed the inspiration for Koch’s own program,
and the two scientists have been working closely together ever since.
On a muggy day this summer, I visit Koch and his mentor at Crick’s rambling
ranch-style home in La Jolla. Though Crick has lived 30 years in California,
where he is based at the Salk Institute, he remains an Englishman through and
through. Tall and majestic, he radiates an aura of noblesse oblige, though,
uncommonly for a scientist of his iconic stature, there is nothing snobbish
about him. At 84, Crick still seems to be sucking in the world with the wonder
of a precocious child. Now suffering from advanced cancer, he walks with a
stick, but during three hours of conversation he blazes forth with ideas and
fiercely held opinions. One gets the feeling that if the inexorable hand of the
biological clock were not ticking so loudly, he could live yet another life with
just as spectacular results.
Crick has never been one to dream small. Sitting in his study overlooking a
lush, rose-filled garden and surrounded by the latest issues of a dozen research
journals, he talks about the goals he set himself as a young man in the 1940s.
There were two problems that interested him, he says: “the borderline between
the living and the nonliving,” and the nature of consciousness. Amazingly, it
took just four years — from 1949 to 1953 — for him and James Watson to elucidate
the structure of DNA, thereby solving the mystery by which living things encode
their own blueprint. Fifty years later, Crick still seems awestruck by this
discovery. “That was a fluke,” he tells me. “I thought this problem would take
me the rest of my life.” No one then imagined that the structure of the DNA
molecule would turn out to be so critical to genetics: “It could have been a
very boring structure.”
Instead, when he and Watson first divined the double helix, they immediately
recognized that, in this twinned spiral, nature had found a miraculous means to
store and implement its genetic code. Since each helix carries a complete copy
of this code, the double spiral could be unzipped — thus one side could
be replicated and restored, while the other side is put into action synthesizing
proteins. Watson and Crick’s astonishing revelation about DNA was that the
form of the molecular chain encompassed not only its code but also its
function.
Having found the material structure underlying life (and since then made a
slew of further discoveries in molecular biochemistry), Crick began to think
about his other great interest. Might it be possible to find the material
structures underlying the mind? “When I came to the Salk Institute,” he says, “I
told them that I wanted to work on the brain.”
Crick began by studying the visual system of primates, a fairly conventional
area of research at the time. Yet although scientists were trying to understand
the process of visual awareness, the monkeys they tested were always unconscious.
Crick became disenchanted. If understanding consciousness was the goal, surely
that state should be the minimal requirement for test subjects. In 1980, when he
received a million-dollar grant to set up a visiting-scholars program at the
Salk Institute, he began to invite in other researchers to strategize about new
approaches to the science of mind. One of his first invitations went to Christof
Koch.
4. NEURAL LEARNING
Many contemporary philosophers of the mind assume that consciousness must be
a phenomenon involving the entire brain, or at least large parts of it. Crick
and Koch believe, however, that awareness is a local phenomenon emerging from
the behavior of small networks or “coalitions” of neurons interacting. Because
only a tiny number of neurons may be involved at any point in time, Koch notes,
the physiological signature of consciousness might be quite difficult to find.
Crick and Koch’s biggest challenge is to design experiments with enough rigor to
tease out the conscious from the unconscious levels of perception.
At Koch’s Caltech lab, I am invited to sit in on a test session in which a
student volunteer lends his mind to research by allowing his body to be zapped
with electric shocks. In charge of the experiment is R. Mckell Carter, an
intense young doctoral student who speaks even faster than Koch. Like his
mentor, Carter is a rock climber, and he moves with the easy grace of someone
who feels comfortable in his skin. Carter’s research revolves around classical
Pavlovian conditioning, in which subjects learn to associate two sensory
phenomena — say, the sound of a bell with the smell of food. These days, one of
the stimuli is often a mild electric shock. In the experiment I am to observe,
the subject is asked to look at a computer screen on which images of animals
flash. Some of the images are preceded by a shock, and the question is to what
extent the subject can learn to anticipate when the shock will occur. It’s the
unconscious mind that registers first, by triggering a sharp rise in skin
conductance on the palms. (When we are stressed, our palms sweat and the skin
becomes more conductive.)
Today’s volunteer is Jim, a tall, dark-eyed sophomore. Once he’s wired —
electrodes on the right hand, sensors on the left hand — Carter proceeds to
determine the appropriate level of electrical bite. “You want it to be the
maximum level of discomfort that the subject can tolerate without it being
painful,” he deadpans. For reasons that are not understood, people have wildly
different responses to the shocks. The head of Caltech’s Human Safety Committee
“maxed out” the machine, Carter tells me — even at full charge, the shocks
didn’t bother him at all. I tanked a mere third of the way up the scale. Jim
settles on a point around the two-thirds mark. Now he is asked to rest his head
in a stand so that Carter can track the motion of his eyes. In all, he’ll be
monitored by three computers, though with the electrodes dangling from his arms
and the metal contraption cradling his head, the whole setup looks as if it’s
been devised by Victor Frankenstein.
Jim is now ready to begin. Soon elephants and butterflies are flashing across
the screen. Halfway through the test, it’s clear his unconscious is learning its
stuff — the skin-conductance peaks are beginning to appear before the shocks
hit, which means that somewhere in his mind neurons have learned when to expect
these jolts. This is a brand-new experiment, Carter tells me. They get to study
both “trace” and “delay” conditioning at once, giving them an unprecedented
window into some of the unconscious mechanisms of perception.
Yet if Koch’s team is beginning to reveal the physiological footprints of our
most intimate mental state, the question remains: How do the material processes
they are discovering give rise to subjective states of mind? How is it
that neuronal spiking in response to, say, the color red gives rise to the rich
subjective experience of “seeing” red, the full-on panoply of feeling
that philosophers refer to as qualia — the redness of red, the painfulness of
pain and so on? For all our advances in neuroscience, Oliver Sacks wrote in a
recent essay, “Neuronal activity and psychic activity still seem utterly
different,” even “incommensurable” in kind.
In their Nature article, Crick and Koch frankly admit their ignorance:
“No one has produced any plausible explanation of how the experience of the
redness of red could arise from the actions of the brain,” they write. In short,
the mind-body problem remains as intractable as ever. Crick and Koch’s
innovation has been to sidestep the grand philosophical dilemma — what Chalmers
calls the “hard problem” — and to get on with the mundane field work. Rather
than try to explain how consciousness arises, or even what consciousness
is, they have confined themselves to identifying the neurological
conditions under which consciousness is present.
Koch draws a parallel with the discovery of the double helix and the
subsequent development of gene science. In the early 1950s, he points out, “No
one had much idea what a gene was,” but the discovery of the physical structure
of DNA provided a foundation on which to investigate the question. Half a
century later, geneticists have cataloged most of the human genome; they can
insert, delete and alter individual genes at will. Just as an understanding of
the physical basis of heredity revolutionized our view of life, so, Crick and
Koch believe, understanding the material processes behind consciousness will
lead eventually to a comprehensive and applicable theory of mind.
5. RETURN OF THE ZOMBIES
“I know of no logical reason why you couldn’t be a zombie,” Koch declares
amiably as we chat one morning in the Caltech cafeteria. Considering my insomnia
the night before, I must admit to feeling less than fully present. Koch,
however, is jazzed as ever and about to embark on another “awesome” climbing
trip to Zion National Monument, where he and Zinn will rappel down a 1,500-foot
canyon, at times having to travel from one drop to the next underwater. In
addition to a heavy load of climbing tackle, they’ll be hauling wetsuits.
Whatever doubts I harbor about myself, I am pretty certain that anyone who can
think through such an operation is unlikely to be a zombie. The idea of planning
is in fact central to Crick and Koch’s thesis about the purpose of
consciousness.
In principle, Koch says, there is no reason why consciousness is necessary to
life. With enough “input sensors and output effectors,” it is conceivable that
“A zombie could pretty much do anything.” But since every zombie behavior must
be hard-wired, the more situations it must respond to, the more complex its
internal mechanism must become. Instead, “Evolution has chosen a different path,
synthesizing a much more powerful and flexible system” that we call
“consciousness.” The main function of this innovation, he and Crick propose, is
to enable organisms to deal rapidly with unexpected events and to plan for the
future. As Koch likes to say, consciousness puts us “online,” allowing us to
override our instinctual “offline” programming.
Within Crick and Koch’s scheme, the neural correlates of consciousness map
the things in an organism’s environment of which it is currently aware. As my
awareness flits from, say, the cup of coffee in front of me to the sound of a
bird singing outside, the contents of this “cache memory” change. Thus, Crick
and Koch propose that consciousness is innately linked to short-term memory.
That linkage is key, Koch says, for it suggests what he refers to as “an
operationalized test” for consciousness. Since zombie agents operate purely
according to preprogrammed rules, a zombie would have no need for short-term
memory, and hence Koch believes the absence of this feature would serve as an
indication that consciousness was also missing.
Consider the following situation: You see an outstretched hand, but instead
of shaking it immediately, which instinct would dictate, you are required to
close your eyes and wait several seconds before doing so. Koch and Crick suspect
that without a short-term memory, a zombie could not do this task, or any other
in which an artificial delay was imposed between “an input and the associated
motor output.” Absence, like presence, has a neurological signature, and Koch
imagines a kind of “conscious-ometer” that could be used to measure who and what
is consciously aware.
One immediate application would be anesthesiology: When is a patient about to
undergo surgery truly out? But in The Quest for Consciousness, due out in
January, Koch also suggests more controversial applications. When does
consciousness arise? he asks. Is it present in the newborn child? Or does it
gradually emerge? And if so, at what stage in the infant’s development? At the
other end of life’s continuum, does consciousness gradually fade as dementia
sets in, or does it linger in diminished form until the bitter end? With an
operationalized test, he writes, we could “monitor the presence of consciousness
in premature babies and young infants, in patients whose minds are afflicted
with severe autism or senile dementia, and in patients who are too injured to
speak or even to signal.” As a practicing Catholic who attends Mass every
Sunday, Koch is haunted by the question of life’s end; his father died while
suffering from Parkinson’s disease, and that long drawn-out mental decline
etched itself deeply into his son’s psyche. “Wouldn’t you want to know if
someone you loved was conscious or not?” he demands.
A conscious-ometer could also be applied to animals. Every morning Koch goes
running with one of his three large dogs, and there is no doubt in his mind that
they are extremely aware. How far down the animal kingdom does the trait extend?
“Is a fly conscious?” Koch asks. “Is a bee?” Recent evidence from an Australian
researcher reveals that bees possess an ability to learn complex navigational
cues: Koch suspects that to some extent they must be aware.
Koch’s conscious-ometer is more than a mere thought-experiment; he genuinely
hopes to build one. For the moment, he is concentrating not on humans but on
biology’s most common test subject, the mouse. He and his colleagues are trying
to develop “a mouse model of consciousness,” a rigorous way of determining if
and when a mouse is aware. Over the past decade, biologists have learned how to
turn individual genes on and off in the developing rodent fetus. With a mouse
model of consciousness, Koch could begin to explore what genes are essential for
this phenomenon. One question he would like to pursue is whether it is possible
to genetically engineer an animal without conscious awareness — a zombie
mouse.
Several years ago, Koch tells me, one of his best friends, a schizophrenic,
committed suicide. It was an act that he finds almost incomprehensible and, as a
Catholic, deeply disturbing. “If we want to understand the human mind and all
the suffering it is subject to, then we have to understand its
physiological basis,” he says, his voice rising with a sense of urgency. Koch
ends his book with a call for a scientific theory “that accounts for what
organisms, under what conditions generate subjective feelings;
what purpose they serve, and how they come about.” Whether science
can finally breach the gap between “matter” and “mind” — a category division
that some argue is a disaster of its own making — remains to be seen. Two
thousand years of history suggest the problem has depths that will not easily be
plumbed by any physiological probe. But if in the 21st century somebody finally
does understand the emergence of consciousness from the neurochemical mass of
our brains, he or she will no doubt owe a debt to Christof Koch.
What Does a Neuron See?
Human beings are exceptionally good at visual perception — we can
easily distinguish among thousands of faces, even ones we’ve never seen before.
The best computer vision systems struggle with this problem and are usually
fooled by simple disguises, or merely a change in lighting. How do our brains
piece images together? What is going on at the neuronal level that makes us so
skilled at this task? For years, vision researchers have been experimenting with
animals, including monkeys, measuring the output from single neurons through
probes embedded in their brains.
But you can’t stick probes into human brains — at least not under normal
circumstances. There is, however, a small cohort of epileptics whose condition
requires surgery, and in preparation for that procedure electrodes are implanted
beneath their skulls to gather information about the seizures. Such patients
provide a unique opportunity for researchers to observe brain function directly.
Christof Koch’s graduate student Leila Reddy has been working with a group of
such patients at UCLA’s Cognitive Neurophysiology Laboratory under renowned
surgeon Itzhak Fried.
A diagnostic cranial implant will typically contain 64 electrodes, each one a
microthin wire that can potentially record the output of a single neuron. In
practice, however, signals from neighboring neurons often blur together, and
Reddy says she is lucky to get more than a couple of useful signals from each
run. Moreover, patients awaiting brain surgery can’t be expected to endlessly
look at pictures, so while most are very receptive to the research, time
constraints are critical. Yet even under these conditions, Reddy and her
predecessor Gabriel Kreiman have made some startling discoveries.
It turns out that in the medial temporal lobe many neurons respond
only to specific categories of images. Fifteen percent seem to respond
exclusively to faces or animals. It’s as if we are hard-wired to see them.
That’s not surprising, Koch says, when you consider that “For most of human
history, animals would have been either predators or lunch.” But how specific is
our visual machinery? Kreiman, who is now at MIT, discovered that it can be
highly specific. One neuron he recorded fired only when the patient was shown
pictures of the Three Stooges’ Curly. In another patient, Kreiman found a neuron
that responded only to images of Bill Clinton. “We don’t know how it would have
reacted to Monica Lewinsky,” Reddy notes slyly.
At this early stage, it’s important not to make too grandiose claims, Reddy
cautions, but the research bolsters Koch’s thesis that within the brain,
consciousness is a local phenomenon. Kreiman showed that many neurons will
respond only when we are consciously aware of the image we’re
looking at. Reddy is now embarking on a series of experiments to determine if
there are also neurons that fire when the patient isn’t aware. According
to Koch’s new theory of mind, most of our brain is not involved in the state of
conscious awareness. What Reddy is hoping to find is the empirical signature of
this “zombie self.”
