A vegetative-state patient, who has been behaviorally unresponsive for 16 years, showed remarkably similar brain activity as healthy volunteers when viewing Alfred Hitchcock clips. Using brain imaging, researchers may have discovered a common neural code that underlies the conscious experiences we share, even in the absence of behavioral responses.
Interpreting human consciousness based on brain activity (and without speech or actions) is a major challenge of modern neuroscience. The new study, published in Proceedings of the National Academy of Sciences this week, could help detect if a patient who’s unable to respond is actually conscious -- and maybe even what they’re thinking, though that’s a stretch for now.
Using fMRI, Lorina Nacia and colleagues from the University of Western Ontario examined neural activity in 12 healthy participants and two behaviorally unresponsive, brain-injured individuals with unknown levels of consciousness as they each viewed edited sequences of “Alfred Hitchcock Presents -- Bang! You’re Dead.” In this 1961 black-and-white TV episode, a child carries a partially loaded revolver around town. All the participants had to do was watch and follow along as best as they could.
Across all the healthy participants, watching the short 8-minute film elicited a common pattern of synchronized neural activity in the frontal and parietal brain regions involved in high-level cognitive processes. These include monitoring and analyzing information in our surroundings. Activity in these regions was stronger during the highly suspenseful movie moments -- which imposed greater cognitive demands in terms of understanding the plot -- compared with the less suspenseful frames that required less executive processing.
Viewing the thriller didn’t evoke activity in the frontal and parietal regions of one of the brain injury patients, a 20-year-old woman. She showed patterns of brain activity only in sensory (and not executive) areas, Nature reports. The pattern of brain activity in the second patient, however, resembled that of healthy participants (pictured to the right) -- in particular, their executive engagement and moment-to-moment perception of the movie's content.
Even though the 34-year-old man had been entirely unresponsive since he was a teenager, these findings indicate that he was consciously aware and possibly able to follow the movie plot. “It was actually indistinguishable from a healthy participant watching the movie,” study coauthor Adrian Owen of Western University tells Nature.
The findings suggest a common neural basis of human consciousness and allows for the interpretation of conscious experience in the absence of behavioral responses. "For the first time, we show that a patient with unknown levels of consciousness can monitor and analyze information from their environment, in the same way as healthy individuals," Naci explains in a news release. "We already know that up to one in five of these patients are misdiagnosed as being unconscious and this new technique may reveal that that number is even higher."
Images: Western University (top), Lorina Naci (middle)