Emblems of Awareness: Brain Signatures Lead Scientists to the Seat of Consciousness
Sanders, Laura, Science News
Humankind's sharpest minds have figured out some of nature's deepest secrets. Why the sun shines. How humans evolved from single-celled life. Why an apple falls to the ground. Humans have conceived and built giant telescopes that glimpse galaxies billions of light-years away and microscopes that illuminate the contours of a single atom. Yet the peculiar quality that enabled such flashes of scientific insight and grand achievements remains a mystery: consciousness.
Though in some ways deeply familiar, consciousness is at the same time foreign to those in its possession. Deciphering the cryptic machinations of the brain--and how they create a mind--poses one of the last great challenges facing the scientific world.
For a long time, the very question was considered to be in poor taste, acceptable for philosophical musing but outside the bounds of real science. Whispers of the C-word were met with scorn in polite scientific society.
Toward the end of the last century, though, sentiment shifted as some respectable scientists began saying the C-word out loud. Initially these discussions were tantalizing but hazy: Like kids parroting a dirty word without knowing what it means, scientists speculated on what consciousness is without any real data. After a while, though, researchers developed ways to turn their instruments inward to study the very thing that was doing the studying.
Today consciousness research has become a passion for many scientists, and not just for the thrill of saying a naughty word. A flood of data is sweeping brain scientists far beyond their intuitions, for the first time enabling meaningful evidence-based discussions about the nature of consciousness.
"You're not condemned to walk around in this epistemological fog where it's all just sort of philosophy and speculation," says neuroscientist Christof Koch of Caltech and the Allen Institute for Brain Science in Seattle. "It used to be the case, but now we can attack this question experimentally, using the tools of good old science to try to come to grips with it."
Knowledge emerging from all of this work has ushered researchers into a rich cycle of progress. New experimental results have guided theoretical concepts of consciousness, which themselves churn out predictions that can be tested with more refined experiments. Ultimately, these new insights could answer questions such as whether animals, or the Internet, or the next-generation iPhone could ever possess consciousness.
Though a detailed definition remains elusive, in simplest terms, consciousness is what you lose when you fall into a deep sleep at night and what you gain when you wake up in the morning. A brain that is fully awake and constructing experiences is said to be fully conscious. By comparing such brains with others that are in altered states of awareness, researchers are identifying some of the key ingredients that a conscious brain requires.
In the hunt for these ingredients, "we decided to go for big changes in consciousness," says Giulio Tononi of the University of Wisconsin-Madison. He and others are studying brains that are deeply asleep, under anesthesia or even in comas, searching for dimmer switches that dial global levels of consciousness up or down.
Scrutinizing brain changes that correspond to such levels has led some scientists to a central hub deep in the brain. Called the thalamus, this structure is responsible for constantly sending and receiving a torrent of neural missives. Other clues to consciousness come from a particular kind of electrical signal that the brain produces when it becomes aware of something in the outside world. But rather than one kind of signature, or one strategic brain structure, consciousness depends on many regions and signals working in concert. The key maybe in the exquisitely complicated ebb and flow of the brain's trillions of connections. …