Their research, published in the online journal PLOS Computational Biology, is paving the way toward developing a scientific definition of consciousness.
“In terms of brain function, the difference between being conscious and unconscious is a bit like the difference between driving from Los Angeles to New York in a straight line versus having to cover the same route hopping on and off several buses that force you to take a ‘zig-zag’ route and stop in several places,” said lead study author Martin Monti, Ph.D., an assistant professor of psychology and neurosurgery at UCLA.
The researchers used functional magnetic resonance imaging (fMRI) to investigate how the flow of information changed in the brains of 12 healthy participants (ages 18-31) as they lost consciousness under anesthesia with propofol. The participants were evenly divided between men and women.
Using a branch of mathematics known as graph theory, the psychologists analyzed the “network properties” of the subjects’ brains.
“It turns out that when we lose consciousness, the communication among areas of the brain becomes extremely inefficient, as if suddenly each area of the brain became very distant from every other, making it difficult for information to travel from one place to another,” Monti said.
The finding shows that consciousness does not “live” in a particular place in our brain but rather “arises from the mode in which billions of neurons communicate with one another,” he said.
When individuals experience severe brain damage and enter a coma or a vegetative state, Monti said, it is very likely that the sustained damage hinders their normal brain function and the emergence of consciousness in the same way observed in the healthy volunteers under anesthesia.
“If this were indeed the case, we could imagine in the future using our technique to monitor whether interventions are helping patients recover consciousness,” he said.
“It could, however, also be the case that losing consciousness because of brain injury affects brain function through different mechanisms.”
“As profoundly defining of our mind as consciousness is, without having a scientific definition of this phenomenon, it is extremely difficult to study,” Monti noted. This study, he said, marks an initial step toward conducting neuroscience research on consciousness.
The research was conducted at Belgium’s University Hospital of Liege.