Consciousness: science's biggest mystery: the quest to understand consciousness has captured the imaginations of cognitive neuroscientists, psychologists and philosophers, who tend to line up on either side of a classic matter-spirit divide

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A baffling and profound mystery lies at the heart of one of the fastest-growing research areas in science today.

The mystery is human consciousness and how--or even whether--it arises out of our fleshy brains. How does it happen that billions of nerve cells collaborate in an organ no bigger than haft a football, allowing us not only to navigate intricate math equations and entertain elaborate thoughts, but to observe ourselves as we perform such functions, to feel exquisite emotions that a computer couldn't begin to comprehend?

It is a fascinating field of study that is luring some of the nation's best and brightest scientists, including some with a religious bent. They are drawn because they know that the explanation, when it comes, will be as stunningly mind-boggling as the discovery of DNA or the development of quantum physics. And--because it stands to potentially overthrow the reigning scientific assumption that everything has a material explanation--it could unite science and religion in a way no discovery has before.

Scientists know a lot about the brain's structure and functions, yet know next to nothing about the process that leads to the clear sense of identity that emerges from our experiences and to our richly diverse inner lives.

Consciousness is not simply the opposite of unconsciousness. It involves a definite sense that someone is in the driver's seat, an executive "I" who constantly monitors input from the senses, from inner states, from emotions, from the environment, then orders behavior and speech with access to both a memory library and an imagination.

It is comprised of our sense of identity, location and time, of our perceptions of the world around us, the memories that lace our stories and beliefs about the world, our emotional states and inclinations, our capacity to direct perceptions and thoughts, our sense of well-being, our zest for life, and much more. Consciousness is the brain's overall awareness of the competing claims of all that information at any given time.

The quest to understand it has captured the imaginations of cognitive neuroscientists, psychologists and philosophers, who tend to line up on either side of a classic matter-spirit divide.

Those holding to the "materialist" view contend that the overwhelming evidence points to consciousness as a product of the inert gray matter in our skulls and nothing more. Harvard psychologist Steven Pinker asserts that "the supposedly immaterial soul we now know can be bisected with a knife, altered by chemicals, started or stopped by electricity, and extinguished by a sharp blow or by insufficient oxygen."

But there's another group willing to consider an alternative view, one found in many spiritual traditions: that consciousness arises from something beyond the material world; that it is conceivably a key component of the cosmos, as fundamental as space, time and matter.

As answers are found, they may bridge the gap in scientific worldviews. But for now, both groups agree that ethical and religious questions abound in the area of consciousness research. "Questions once confined to theological speculations and late-night dorm room bull sessions are now at the forefront," Pinker says.

At what point does a fetus acquire consciousness? Could we "raise" a mind like pioneers raised a barn, by building a sufficiently intricate machine? Is a cat's mind quantitatively or qualitatively different from ours? What kind of consciousness exists in the partly fused brains of a pair of Siamese twins? When the physiological activity of the brain finally ceases, does that executive "I" go entirely out of existence?

Pinker describes the current state of research: "With some problems a modicum of consensus has taken shape. With others, the puzzlement is so deep that they may never be resolved. Some of our deepest convictions about what it means to be human have been shaken. It shouldn't be surprising that research on consciousness is alternately exhilarating and disturbing. No other topic is like it."

Cognitive neuroscientists agree that it's a field that still awaits its Einstein or its Francis Crick, the co-discoverer of DNA. In fact, Crick himself was working in the area of cognitive neuroscience until he died in 2004.

Woven on an enchanted loom

The physical building blocks of the mind are neurons, highly specialized, electrically excitable nerve cells down which voltage travels. Those currents are sent down the axon, a long stalk for transmitting the information over distance. At the axon's tip are treelike branching dendrites receiving signals from other neurons. The information jumps between the neurons across synapses by means of chemical transmitters.

The result is a rich tapestry woven together moment by moment on the brain's enchanted loom. It cannot be located in one specific area of that organ, scientists say. It's distributed over many parts and perhaps beyond.