A telltale signature of consciousness has been detected that takes us a step closer to disentangling the brain activity underlying conscious and unconscious brain processes.
It turns out that there is a similar pattern of neural activity each time we become conscious of the same picture, but not if we process information from the image unconsciously. These contrasting patterns of activity can now be detected via brain scans, and could one day help determine if patients with brain damage are conscious. They might even be used to probe consciousness in animals.
“It's very exciting work,” says neuroscientist Raphaël Gaillard of the University of Cambridge, who was not involved in the work. “The use of a reproducibility measure to disentangle conscious and non-conscious processes is genuinely new.” Gaillard has previously shown that coordinated activity across the entire brain is one of the signatures of consciousness .
So far, efforts to find a brain signature of consciousness have focused on the intensity of neural activity, how long it lasts, and whether signals tend to be synchronised across different regions of the brain.
“We were looking for something other than the intensity and duration of the neural activity that characterises conscious neural processing,” says Aaron Schurger of Princeton University in New Jersey, who led the new work.
He and his colleagues hypothesised that when the brain is presented with the same sensory input – a picture, say – time after time, then conscious awareness of the picture should produce similar neural activity each time.
Conversely, if the sensory input did not enter conscious awareness, it should produce different brain activity each time because there would be other subconscious processes going on at the same time.