by Tanya Lewis
Probably for as long as humans have been able to grasp the concept of consciousness, they have sought to understand the phenomenon.
the mind was once the province of philosophers, some of whom still believe the subject is inherently unknowable. But neuroscientists are making strides in developing a true science of the self.
Here are some of the best contenders for a theory of consciousness.
Cogito ergo sum
Not an easy concept to define, consciousness has been described as the state of being awake and aware of what is happening around you, and of having a sense of self. [Top 10 Mysteries of the Mind]
The 17th century French philosopher René Descartes proposed the notion of "cogito ergo sum" ("I think, therefore I am"), the idea that the mere act of thinking about one's existence proves there is someone there to do the thinking.
Descartes also believed the mind was separate from the material body — a concept known as mind-body duality — and that these realms interact in the brain's pineal gland. Scientists now reject the latter idea, but some thinkers still support the notion that the mind is somehow removed from the physical world.
But while philosophical approaches can be useful, they do not constitute testable theories of consciousness, scientists say.
"The only thing you know is, 'I am conscious.' Any theory has to start with that," said Christof Koch, a neuroscientist and the chief scientific officer at the Allen Institute for Neuroscience in Seattle.
Correlates of consciousness
In the last few decades, neuroscientists have begun to attack the problem of understanding consciousness from an evidence-based perspective. Many researchers have sought to discover specific neurons or behaviors that are linked to conscious experiences.
Recently, researchers discovered a brain area that acts as a kind of on-off switch for the brain. When they electrically stimulated this region, called the claustrum, the patient became unconscious instantly. In fact, Koch and Francis Crick, the molecular biologist who famously helped discover the double-helix structure of DNA, had previously hypothesized that this region might integrate information across different parts of the brain, like the conductor of a symphony.
But looking for neural or behavioral connections to consciousness isn't enough, Koch said. For example, such connections don't explain why the cerebellum, the part of the brain at the back of the skull that coordinates muscle activity, doesn't give rise to consciousness, while the cerebral cortex (the brain's outermost layer) does. This is the case even though the cerebellum contains more neurons than the cerebral cortex.
Nor do these explain how to tell whether consciousness is present, such as in brain-damaged patients, other animals or even . [Super-Intelligent Machines: 7 Robotic Futures]
Neuroscience needs a theory of consciousness that explains what the phenomenon is and what kinds of entities possess it, Koch said. And currently, only two theories exist that the neuroscience community takes seriously, he said.