Scientists say they’ve discovered a totally new kind of brain activity lurking beyond the “flat-lined” state seen in deep comas.
A team of Canadian and Romanian researchers found evidence of cerebral activity both in a human coma patient and in 26 cats induced by drugs into an incredibly deep (but reversible) coma. They describe the new phenomenon, which they’ve dubbed “Nu-complexes,” in a paper published Wednesday in the journal PLoS ONE.
Initial stages of comas are comparable to deep sleep, but if a person progresses into a deeper and deeper quietude, the brain state alters more dramatically. In cases of very deep comas, an electroencephalogram (EEG) monitor will render a flat line (also called an isoelectric line), marking a state in which the brain’s electrical activity has either stopped or is so low it is virtually undetectable. This is considered one of the boundary lines between having a living brain and brain death, but is not the only criteria that doctors use to declare someone brain-dead; there usually has to be evidence of structural damages in the brain as well.
This new research suggests that cerebral activity can revive after the flat-lined state, under certain conditions. The work started when Romanian doctor and study coauthor Bodan Florea observed unusual brain activity in a hospital patient who went into a coma following a heart attack.
Florea and two University of Montreal researchers decided to try and re-create the human patient’s brain state in animals. They pushed laboratory cats to the flat-lined state with an anesthetic called isoflurane. When they gave the cats doses of the drug even higher than the amount that induces a flat EEG line, they saw “a re-vitalization of activity in the brain,” marked by the appearance of sharp EEG waves in all 26 subjects. The brain activity revealed itself to be oscillations stemming from the hippocampus -- a brain area associated with memory and learning -- and sent to the cortex. The team believes these waves, or Nu-complexes, match the brain state of the human patient.
“Nu-complexes appear in a deeper state of coma, provided that neurons are well-fed, well-supplied with blood and oxygen and in good shape,” senior author Florin Amzica said in a phone interview.
The find, Amzica says, is a new frontier in brain research. There are still many remaining questions about the kind of extra-deep coma that gives rise to Nu-complex. It is even possible that this kind of brain activity might even keep a brain from “atrophying” after a long period of coma.
“We want to know if this state is beneficial for the brain,” Amzica says. Though “at this point we don’t know if any [brain] modifications are set into motion by such a deep coma.”
However, the team wants to caution people not to interpret their study as a sign that, perhaps, one’s brain-dead relative was actually alive.
"Those who have decided to or have to 'unplug' a near-brain-dead relative needn't worry or doubt their doctor,” Amzica said in a statement. “The current criteria for diagnosing brain death are extremely stringent. Our finding may perhaps in the long term lead to a redefinition of the criteria, but we are far from that. Moreover, this is not the most important or useful aspect of our study.”
SOURCE: Kroeger et al. “Human Brain Activity Patterns beyond the Isoelectric Line of Extreme Deep Coma.” PLoS ONE published 18 September 2013.
Roxanne has liked science ever since she started watching "Bill Nye the Science Guy" on Saturday mornings over a bowl of sucrotic O's. She especially likes writing about...