Elusive On/Off Switch Found for Human Consciousness
When I was a child about nine years old or so, I embarked on a mission to discover the barrier between waking and sleeping. I believed that if I concentrated each night before falling asleep, I would recognize the moment I slipped out of consciousness and into dream. I never found the precise line — although I did, unintentionally, teach myself to lucid dream.
But now there is research showing that the brain does have an on/off switch that triggers unconsciousness. Mohamad Koubeissi at the George Washington University in Washington DC and his colleagues describe for the first time a way to switch off consciousness by electrically stimulating a part of the brain called the claustrum.
Their accidental discovery could lead to a deeper understanding of a fundamental mystery of the human brain; that is, how conscious awareness arises.
The discovery came while the researchers were studying a woman who has epilepsy. During a procedure, they used deep brain electrodes to record signals from different parts of her brain in order to determine where here seizures were originating. One electrode was place next to the claustrum, a thin, sheet-like structure underneath the neocortex. Although this area has never been electrically stimulated before, it had been implicated in the past as a possible control center for consciousness by neuroscientist Francis Crick, who identified the structure of DNA, and his colleague Christof Koch of the Allen Institute for Brain Science in Seattle.
Koubeissi and his team found that Crick and Koch might have been on to something. When they stimulated the area with electrical impulses from the brain electrodes, the woman stopped reading, stared blankly into space and didn’t respond to auditory or visual commands. Her breathing slowed as well. She had lost consciousness. When the scientists turned off the electrical stimuli, she immediately regained consciousness with no memory of blanking out. Additional attempts were tried over two days and each time, the same thing happened.
New Scientist reported on the results and in the article Koubeissi says he thinks the claustrum indeed plays a vital role in triggering conscious. “I would liken it to a car,” he told New Scientist reporter Helen Thompson.
“A car on the road has many parts that facilitate its movement – the gas, the transmission, the engine – but there’s only one spot where you turn the key and it all switches on and works together. So while consciousness is a complicated process created via many structures and networks – we may have found the key.”
One researcher, Anil Seth, who studies consciousness at the University of Sussex, UK, pointed out that the woman in the study had had part of her hippocampus removed earlier as a way to treat her epilepsy, so she doesn’t represent a “normal” brain.
Additional research is needed. But the results could open wide a door on one of the most mysterious aspects of existence. We could determine once and for all what living creatures are aware of themselves and the world around them.
Credit: PASIEKA/Science Photo Library/Corbis