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Of Chemistry and Consciousness

By Harrison Wein

On the Front Page...

The concept of consciousness is familiar to us all, but it may be the most mysterious feature of our existence. What exactly is consciousness? What gives us this self-awareness? Are our minds somehow separate from our bodies, destined never to be explained by science? These questions have occupied philosophers and artists ranging from the writings of Kant and Hegel to movies like Arnold Schwarzenegger's Total Recall.


Scientists are now finally glimpsing brain activity that they believe is associated with consciousness, yet many people question whether we can ever have real answers. "Scientific Approaches to Consciousness: Reductionism Debated," a symposium organized by the National Institute of Mental Health and held on May 10 in the Natcher Conference Center, brought together four of the leading researchers — two scientists and two philosophers — in the field of consciousness. They explored whether our sense of consciousness could ever be reduced to a set of nerve cells (or neurons) and chemical interactions in the brain.

"More people are exploring a wider variety of approaches and producing a greater number of new insights into consciousness than ever before," said Dr. Howard S. Kurtzman, chief of the Cognitive Science Program at NIMH and moderator of the seminar. But despite all this progress, he said, "It is not obvious how consciousness can be understood within the frameworks of psychological science and neuroscience...Consciousness poses probably the greatest challenge to reductionist approaches."

Reductionism Debated

The history of science is littered with problems thought to be insoluble and immune to a reductionist approach. Dr. Patricia S. Churchland, a philosopher from the University of California at San Diego, challenged the audience, "The fact that you yourself can't imagine the solution doesn't mean a whole lot." Heat, related to the movement of molecules, is one example of a phenomenon people thought could never be explained. Until people understood what molecules were and that faster-moving molecules caused higher temperatures, they found it inconceivable that temperature could ever be explained.

Genes and DNA are a similar example brought up by Dr. Christof Koch, a neuroscientist from the California Institute of Technology who is currently collaborating with DNA structure co-discoverer Francis Crick on some of his work. Koch showed a quote from a book published in 1916 and explained that, back then, people couldn't conceive how chromosomes, seemingly indistinguishable from each other, could convey all the properties of life. "We should not make the same mistake twice," he said. Koch assumes that there is a specific circuitry and specific neurons that generate consciousness. He argued, "Once we understand the neural circuitry of the brain it'll become clear why we're conscious."

Not all the speakers agreed. Dr. J. Allan Hobson of Harvard Medical School said, "My intuitive persuasion would be that consciousness will not yield in the way that we hope it will yield. But," he added, "I...never thought that changes in consciousness would yield to a reductionist approach as clearly as they do." Hobson was referring to the difference between waking and dreaming, which he said can be reduced to changes in levels of two kinds of molecules in the brain. He said, "This was something I did not imagine when I was a postdoctoral fellow at the NIH."

Dr. David J. Chalmers, a philosopher at the University of Arizona, was more adamant about the impossibility of ever fully understanding consciousness. Since you can never really know what people are thinking or feeling, how can you ever fully explain consciousness merely in terms of nerve cells and chemicals? "A purely physical explanation will not reductively explain first person data," Chalmers argued. "Close correlations, close associations — that's not enough to count as a reductive explanation...You've got to add in some kind of principle to bridge the gap, some kind of principle relating the two."

This something that Chalmers is talking about is what makes us the thinking, feeling, self-aware people we are. But it is unclear whether there really is something more than a play of language. A neurologist from the audience voiced his doubts: "I think the real problem here is when we start talking about language," he said. "In fact, I specifically blame a little thing with 4 letters: N-E-S-S. That thing is the real problem. When you say redness instead of red, that's the problem. You are putting a lot of stuff there that doesn't exist."

Linguistic Confusion

Ambiguities of language certainly help to confuse this topic. At times, it seemed like people were talking about completely different things. One audience member summed up: "I'm not sure what kind of added value we get by lumping all these things together as consciousness."

Chalmers, whose talk was entitled, "Toward a Non-Reductive Science of Consciousness," said in his introduction, "A lot of people mean a lot of different things when they talk about consciousness."

"Consciousness is kind of an umbrella term that includes various aspects of perception, attention, and knowledge," echoed Kurtzman, the moderator, in a telephone conversation. "The most difficult aspect to describe scientifically is this subjective feeling of consciousness and what that has to do with neurons and material reality. This raw subjectivity is hard to capture."

Starting To Understand Consciousness

Scientists like Koch and Hobson concentrate their efforts on aspects of consciousness that are easier to define and address. Koch, who said he was emboldened by twentieth century molecular biology and cell biology, described his studies into conscious awareness and visual recognition in his talk, "Identifying the Neuronal Correlates of Consciousness."

"Right now you might be conscious of my Arnold Schwarzenegger accent," Koch said in his introduction, "but you're not conscious of other things in the room. Most of the activity in your brain you have no conscious access to. You have no idea how you talk. I don't know how I put the words together. I don't have access to the way I see color, I hear, I analyze language." He asked, "Is there something special about the things you have access to?"

Koch showed how specific neurons in the brain respond to recognized images and the memories of images. For example, certain neurons in one monkey familiar with O.J. Simpson's image "fired" when the monkey saw a picture of Simpson but not of Elvis, Ronald Reagan or others. One neuron in a person's brain fired specifically when he saw an animal. Another fired when a person saw an image or cartoon of a famous person. Another fired at the image of a baseball. Only some of the neurons fired when the people were asked to remember certain images. By looking at these patterns of neuron activity and their overlap, Koch hopes to gain insight into visual consciousness and recognition.

States of Consciousness

Hobson, in his talk "Dreaming and the Brain," took another approach to understanding consciousness, addressing "states" of consciousness between sleeping and waking. Hobson said that levels of consciousness change with levels of activation in the brain. Different regions of the brain have also been linked to different states of consciousness by comparing positron emission tomography brain images of sleeping and waking people. Different sets of chemicals are associated with the sleeping and waking states as well.

"The kind of consciousness we feel," Hobson said, "is actively controlled by the brain stem," the lower stalk of the brain that connects it to the spinal cord. In different sleep states, Hobson explained, the sensory inputs are blocked; at other times the abstract thinking inputs are blocked. Different waking states such as daydreaming, being vigilant, relaxed, or drowsy, are also governed by the brain stem in this way.

"So now we're beginning to get a rather more complete picture of how consciousness changes with changes in the brain state," said Hobson. "Consciousness is the forebrain's representation of the world, our bodies and ourselves, and of course this is the great mystery...we still haven't said how this happens. What we can say is it is always a construction whose level, focus and form depend on the brain stem."

Explaining a Feeling

Yet the work of Koch and Hobson, while intriguing, doesn't begin to explain the more complicated aspects of consciousness — the self-awareness, the raw subjectivity. What makes the redness of red, the pain of headaches, the feeling of emotion, belief, imagination? According to Chalmers, if we don't explain these subjective experiences, the science is incomplete.

Can such things ever be explained? Chalmers says that first person data cannot be subject to the standard method of reductive explanation. We may one day explain how memory works, what neurons are involved in selective attention and what chemicals are associated with emotions, but even then, he argued, there will still be a further question: "Why is the performance of these functions accompanied by subjective experience?"

And herein lies the heart of the debate. Is subjective experience really something different and insoluble, as Chalmers claims, or is it just our egotistical minds that need to believe it is so? When Chalmers polled the audience about it, a majority raised their hands at the question, "Is there a further phenomenon over and above these functions that calls for explanation?" Chalmers noted, "A pretty strong majority say yes, even in this bastion of reductionism."

Churchland couldn't agree less. In her talk "Why Anti-Reductionism Is Wrong," she said, "If you want to argue that consciousness cannot be explained neurobiologically because conscious phenomena are intrinsic, and what intrinsic means for you is it doesn't have any parts and so can't be're just arguing in a circle."

Churchland maintains that scientists will continue to design revealing experiments and eventually explain these seemingly insoluble questions. "I look around at these brilliant graduate students, and I think, 'They've got a good shot at it.'"

In the meantime, research scientists continue to move one small step at a time. Koch explained his approach, "We try to focus on the most simple, basic level of awareness. And maybe once we understand the simple level then everything else will follow, but maybe this requires more complex laws that we still don't understand."

Koch concluded, "Dave [Chalmers] might be perfectly right and it may forever remain beyond a reductionist explanation. That's for the future to see. I'm just taking the working stiff approach."

Further information about the symposium, including access to a video archive of the proceedings, can by found at

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