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Vol. LVII, No. 9
May 6, 2005
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Studies of Consciousness Reawakening, Panel Reports

On the front page...

For many decades considered too obvious, or mysterious, to be studied scientifically, the notion of human consciousness and how it is generated is once again under the microscope, reported a panel of experts convened for a Mar. 22 STEP Science for All session on "Consciousness: How Does the Brain Create Mind?"

The scientists were not all of one mind (heck, the mind itself might not be all of one mind), but a consensus emerged that, in the words of philosopher Dr. Patricia Churchland, "It looks very likely that what we consider mental phenomena is actually brain phenomena.There is no mind-independent substance, just the physical brain" that is responsible for consciousness. "It's not 100 percent certain, but highly probable."

Continued...

 
Dr. Patricia Churchland suggested that we are as naïve today about the true nature of consciousness as the ancients — who thought that the same “element” that consumed firewood also illuminated stars, comets and the northern lights — were about fire.  
That probability is the fruit of broad surveys of neuroscientific study, narrowly focused investigations of an emotion as simple as fear, and on fascinating glimpses into minds damaged by stroke or other brain injury.

Churchland, professor of philosophy at the University of California, San Diego, proceeded on the assumption that "mind is what the brain does," but cautioned that we are far from being able to assign any particular conscious state to the firing of specific neurons. Even so, she argued, "We won't have defined consciousness if all we find are the cortical correlates of it."

Just as fundamental concepts such as temperature, proteins and genes were only understood after years of theoretical fine-tuning — what she called "the profile of discovery" — consciousness itself might one day yield to scientific analysis.

She used the metaphor of fire, which in ancient times was thought to be the root of such disparate phenomena as stars, comets, the northern lights, as well as forest fires, to explain how a definition of consciousness might mature.

We now know that fire is rapid oxidation, she observed, but it has taken millennia to realize that only terrestrial fires depend on oxidation, and that stars are fueled by fusion, comets are cold iceballs lit by starlight, and that no flame ignites the northern lights.

"I suspect that consciousness will go the way of fire," she said. "Neuroscience is still very much in its nascent stages," and cannot yet approach the major puzzles of consciousness, including information storage, modularity, computation, integration, functional organization and time management, she said.

Science's ability to ask good questions about the nature of consciousness has itself been hampered in the past 40 years by a fashionable arm of inquiry known as behaviorism, said Dr. Bernard Baars, a research fellow at the Neurosciences Institute in San Diego. "Consciousness has only been spoken of in euphemisms, as in the way Victorians used to speak of sex." His approach, now more than 2 decades in the making, has been to study consciousness as a variable — states characterized, like gravity, by more and less of it. He has pioneered the concept of "global workspace theory." It posits that the brain — with its 20 billion neurons each firing 10 times per second — is like a "massive society of information processors." Consciousness, in Baars' view, involves brainwide distribution of information; unconscious input stays, by contrast, quite limited in distribution.

 
Speakers at the STEP forum on human consciousness included (from l) Dr. Todd Feinberg, Dr. Joe LeDoux, Churchland and Dr. Bernard Baars.  

Like Churchland, he agrees that it is "too early in the field's history" to arrive at a conceptual definition of consciousness. But just as with fire, and temperature and genes, some fairly smart operational definitions are maturing toward actual concepts.

Interestingly, Baars argued that dreaming is actually a conscious state — studies have shown it (and common sense suggests that humans would have no record of having dreamed if not for this quality).

Lest the discussion become too abstract, Dr. Joe LeDoux of the Center for Neural Science at New York University illuminated the basic neural pathways underlying consciousness of a very raw kind — the sense of fear. Examining the nature of feelings and how the brain makes them, he showed that our emotional responses aren't necessarily dependent on feelings. There are unconscious pre-processes that generate conscious feelings.

If you see a snake, for example, you unconsciously recoil, and only later form an emotion.

LeDoux advanced a "reconsolidation" theory of memory in which our recollections are only as good as the last time they were retrieved; we have no access to the virgin events that originally created them. Perhaps that explains why people habitually revisit bad memories; repeated rinsing might dilute their unpleasantness.

Commenting on the role of the unconscious, LeDoux noted, "There's more to the self than meets the mind's eye."

If consciousness can be defined as self-awareness, what better way to study it than to look at how it changes when damaged by head injury, or stroke or aneurysm? Dr. Todd Feinberg of Albert Einstein College of Medicine offered a clinician's view of the impact of neurological disorders on sense of self.

He focused on delusional mental syndromes in which victims don't recognize their own body parts as belonging to them. In one, married women who are afflicted commonly misidentify the limb as belonging to their husband; men affected by it are likely to attribute ownership to the mother-in-law, he insisted with a straight face.

These conditions, including Capgras syndrome, asomatognosia and alien hand syndrome (in which, in its classical form, a person's hand systematically tries to undo the actions of the other) yield evidence for Feinberg of a "neural hierarchy theory" making consciousness not the king atop a mountain of subservient neurological input, but rather a democracy moved by forces erupting within it.

The four guest speakers might not fully have answered the question, "What is the real nature of conscious awareness?," posed by the meeting's lead organizer, NCI's Dr. Grace Ault, but they certainly reached the borderlands. To see the whole program, visit www.videocast.nih.gov.

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