First Steps toward a Neuroscience of Consciousness

The brain is a complex system, but that doesn’t mean it’s incomprehensible. Our neural circuits were carved by natural selection to solve problems that our ancestors faced during our species’ evolutionary history. Your brain has been molded by evolutionary pressures just as your spleen and eyes have been. And so has your consciousness. Consciousness developed because it was advantageous, but advantageous only in limited amounts.” —David Eagleman

The nature of consciousness has been a core concern of spirituality, particularly Buddhism, for centuries.

Now, psychologists at UCLA have made a first step toward developing a scientific definition of consciousness.

They found that consciousness does not live in a particular place in our brain. Rather, it arises from the mode in which billions of neurons communicate with one another.

Using functional magnetic resonance imaging (fMRI) brain-imaging, researchers investigated what happens to a human brain when it slips into unconsciousness.

“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 ‘zigzag’ route and stop in several places,” said lead author Martin Monti.

Graph Theory and Propofol

The team studied how the flow of information in the brains of 12 healthy volunteers changed as they lost consciousness under anesthesia with propofol. Participants ranged in age from 18 to 31 and were evenly divided between men and women.

The psychologists analyzed the network properties of the subjects’ brains using a branch of mathematics known as graph theory.

Graph theory is often used to study complex systems like air-traffic patterns, information on the Internet and social groups.

“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.

Coma and Vegetative Consciousness

When patients suffer severe brain damage and enter a coma or a vegetative state, Monti said, it is very possible that the sustained damage impairs their normal brain function as well as the emergence of consciousness in the same manner as was seen by the life scientists in the healthy volunteers under anesthesia.

“It could, however, also be the case that losing consciousness because of brain injury affects brain function through different mechanisms,” said Monti. His research team is now addressing this question in another study. “As profoundly defining of our mind as consciousness is, without having a scientific definition of this phenomenon, it is extremely difficult to study.”

This study marks an initial step toward conducting neuroscience research on consciousness.

Monti’s expertise lies in cognitive neuroscience, the relationship between language and thought, and how consciousness is lost and recovered after severe brain injury.

He was part of a team of American and Israeli brain scientists who used fMRI on former Israeli Prime Minister Ariel Sharon in January 2013 to assess his brain responses.

Surprisingly, Sharon, who was presumed to be in a vegetative state since suffering a brain hemorrhage in 2006, showed significant brain activity, Monti reported.

The former prime minister was scanned to assess the extent and quality of his brain processing, using methods recently developed by Monti and his colleagues. The scientists found subtle but encouraging signs of consciousness.

Martin M. Monti, Evan S. Lutkenhoff, Mikail Rubinov, Pierre Boveroux, Audrey Vanhaudenhuyse, Olivia Gosseries, Marie-Aurélie Bruno, Quentin Noirhomme, Mélanie Boly, Steven Laureys.
Dynamic Change of Global and Local Information Processing in Propofol-Induced Loss and Recovery of Consciousness.
PLoS Computational Biology, 2013; 9 (10): e1003271 DOI: 10.1371/journal.pcbi.1003271

Image: Jurgen Ziewe, Wellcome Images