Human consciousness, the lens through which we experience life, is a hard thing to pin down in the brain — especially in people who have experienced traumatic brain injury and can’t tell us that their brains are still executing that essential function.
New research released Wednesday in Science Advances takes a big step forward in identifying brain patterns that act as clues to whether someone may still be experiencing consciousness, even if they can’t tell us themselves.
Scientists hope that by identifying these brain patterns, they may one day be able to help unresponsive patients regain consciousness.
This paper, first-authored by cognitive and clinical neuroscientist Athena Demertzi, Ph.D., is based on existing theories about how the brain produces consciousness. Consciousness, on some level, seems to be associated with brain connectivity. When we’re unconscious, previous studies indicate that regions of the brain turn inward, decreasing communication efforts with other, far-flung regions. When we’re tripping on LSD, the brain produces different types of connectivity, sending lots of signals among regions, a phenomenon that some explain as “altered consciousness”.
But during simple, sober consciousness, the brain steadily sends signals among brain regions and creates an experience of life that is far greater than the sum of its parts.
This paper identifies distinct patterns of brain activity associated with consciousness, which may help illuminate when unresponsive patients are actually switching between conscious and unconscious states:
“Working with families and patients’ caregivers all these years I realize that there is a constant demand for information on what’s happening with their beloved one,” Demertzi tells Inverse. “I consider the clinical relevance of our current findings promising to provide information about the state of consciousness in patients, yet I find they merit further validation before we use them as a clinical biomarker.”
Working from the University of Liége in Belgium, Demertzi began her investigation by taking fMRI images from 159 people, including healthy individuals, people under anesthesia, and patients with unresponsive wakefulness syndrome — a vegetative state in which someone’s eyes are open, but they show no signs of awareness. Demertzi analyzed the activity and connectedness of 42 different brain regions to illuminate the patterns. Overall, she identified four different patterns but found that two seem to be the most useful for determining consciousness.
The first of these is pattern one, which she describes as “the most complex pattern in terms of richness in the way regions communicate with each other.” Pattern one, she explains, is indicative of consciousness in healthy brains. The other pattern she noticed was pattern four, a “low coherence” pattern, meaning that the 42 regions she was tracking weren’t communicating very well. Pattern four, she suggests, indicated unconsciousness (it was commonly found in people under anesthesia) — which fits well with previous findings.
The new part about Demertzi’s study is that she noticed that some unresponsive patients tend to switch from the unresponsive pattern four to the highly responsive pattern one — even for the briefest of seconds.
“What our study indicates is that unresponsive patients, although they predominantly show the low-coherence pattern 4 from which they rarely exit, they also have instances of the complex pattern 1,” she explains. “We therefore wonder whether one day we will be able to spot these momentary brain configurations on time, so our choices for interventions are targeted in more specific ways, by stimulating and hence preserving these upstates of brain configuration.”
In short, she sees that moment when someone’s brain switches gears from the unresponsive pattern four to the potentially healthy pattern one as a unique and important opportunity. If doctors can intervene in that moment, she hope that we may be able to help patients in an unresponsivle state hold on to that pattern of brain activity that is associated with consciousness.
Whether that will actually help them return fully to a wakeful, engaged state is still hard to say, Demertzi admits. She also adds that some families who are trying to decide how to proceed with loved ones in these states could interpret her findings differently. “Some families might consider the ‘presence of consciousness’ hopeful and they would intensify the efforts to restore it, “ she adds. “While others might find it as a severely compromised state so that life is not worth living.”
In either case, this study provides a foundation that others may be able to build upon in the quest to restore permanent consciousness to those who have lost it.
Adopting the framework of brain dynamics as a cornerstone of human consciousness, we determined whether dynamic signal coordination provides specific and generalizable patterns pertaining to conscious and un- conscious states after brain damage. A dynamic pattern of coordinated and anticoordinated functional magnetic resonance imaging signals characterized healthy individuals and minimally conscious patients. The brains of unresponsive patients showed primarily a pattern of low interareal phase coherence mainly mediated by structural connectivity, and had smaller chances to transition between patterns. The complex pattern was further corroborated in patients with covert cognition, who could perform neuroimaging mental imagery tasks, validating this pattern’s implication in consciousness. Anesthesia increased the probability of the less complex pattern to equal levels, validating its implication in unconsciousness. Our results establish that consciousness rests on the brain’s ability to sustain rich brain dynamics and pave the way for determining specific and gen- eralizable fingerprints of conscious and unconscious states.