Saturday, November 29, 2008

Bernard Baars - A Conscious Brain - Meanderings on Human Sentience...

Bernard Baars is a cognitive (neuro)scientist interested in consciousness and related topics like volition and self, their brain basis and evolution, and ethical questions related to them. He's also interested in altered and “higher” states. See Wikipedia entry.

This is a new blog, hosted by Nature Network, but it is off to an interesting start.
A Conscious Brain - Meanderings on Human Sentience...

The very word “consciousness” used to be something of a taboo in the scientific world. But today a growing number of well-known scientists have joined the quest to understand it. The list includes Nobelist Gerald Edelman, Christof Koch, Rodolfo Llinas, Antonio Damasio, and many others. A specialized journal has been running for a decade-and-a-half. A scientific organization, the Association for the Scientific Study of Consciousness, has been holding international conferences for almost as long. Mainstream journals in psychology, brain science, neurology and neighboring fields have joined in.

Twelve years ago Francis Crick published an introductory article in Nature, saying that "the problem of the neural basis of consciousness looks ever more tractable as neurobiologists delve into the process of visual perception."

Crick spent the last decades of his productive life pursuing the notoriously tricky problem of the conscious brain. It was Crick who strongly encouraged pioneering studies on visual consciousness, notably by Nikos Logothetis and his team, using binocular rivalry in macaque monkeys. That continues to be a very productive stream of work today.

Binocular rivalry is an attractive paradigm for the following reason. Try this experiment: Hold one pencil (or another small object) in front of your right eye, and an identical pencil in front of your left eye, both at the same distance, a few inches from each eye. Now see if you can “fuse” the two identical pencils into a single conscious pencil. That simulates binocular vision in nature: We constantly fuse nearly identical views of the same objects in the world around us. We do it so smoothly that we rarely even realize which of our two separate eyes is the dominant or “conscious” one.

But now try a variation. Hold a pencil in front of one eye, and a pen with a different color and shape in front of the other. Do they fuse into a single conscious percept? Not if the experiment is done carefully. The two images will compete with each other if they cannot be perceptually fused.

When two images compete, one tends to be conscious for some time, while the other is suppressed. What happens to the suppressed input? We have good evidence that the unconscious stimulus is still processed to quite a high level in the brain.

Thus the brain receives two nearly identical stimuli, one of which is conscious, the other unconscious. We can now ask the question, “What is the difference between two very similar brain events when only one is reportable as conscious?” Binocular rivalry is the double-slit experiment in the experimental study of consciousness.

Experiments like this have put visual consciousness on the map. Many other methods have now been added. But it’s not just visual awareness alone; we can study consciousness as a state via sleep versus waking, coma and general anesthesia. Or we can study medical conditions like narcolepsy, and the brain chemistry of new “wakefulness” drugs like provigil. We can explore profound puzzles like “blindsight,” the ability of patients with damage to the first visual cortex to spot certain visual events and still hotly deny that they ever really saw them. Other patients lack emotional feelings, or bodily sensations, or the ability to see motion or certain kinds of objects. There are dozens of conditions that dissociate conscious from unconscious brain events. Those natural and experimental dissociations make it possible to study consciousness “as such.”

Today, a PubMed search for “consciousness” brings up 23,142 articles. Not all of them are about consciousness as the major focus, but many are. Then there are the scientific synonyms like “explicit” vs. “implicit cognition,” “supra-” vs. “subliminal stimulation,” “aware” vs. “unaware” conditions and many more. As Science magazine wrote in its 2005 anniverary issue, the “biological basis of consciousness” is now often considered one of the top unsolved problems in science. Unsolved, but not necessarily unsolvable.

Consciousness is back, after a long absence.

This blog - A Conscious Brain - turns the spotlight on a number of recent discoveries and ideas, in a really fun and fast-moving field of science. There is now marked empirical progress, and theories are emerging. It’s still early days; when it comes to the conscious brain we may be living in the early age of science. Yes, we are collecting better evidence, but without a Newton or Copernicus to show how it makes sense. Yet consciousness science is finally back on track. New findings appear every month, testable issues are debated, and normal, healthy science is beginning to grow.

We don’t know that human (or animal) consciousness can ever be understood - but we’ll never know unless we try.

That’s what A Conscious Brain is about.

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