With the help of one man and 26 cats, scientists from the University of Montreal and the Medical Centre Regina Maria in Romania say they've discovered a new frontier in brain function: activity beyond the flat EEG line that has typically signified a person in a very deep coma has become brain dead.
In a study published this week, researchers observed unusual brain activity in the EEG data of a man in a deep coma who was receiving an anti-epileptic medication. The never-before-seen pattern of the electrical waves, which the researchers dubbed Nu-complexes, started in a deeper coma state than EEG activity had ever been observed in before.
Wanting to observe the phenomenon further, the researchers put 26 cats into a reversible deep coma state, past the point of a flat EEG line, when activity in the cortex goes quiet. Every single one of the cats showed activity in the hippocampus, a part of the brain that deals with learning and memory, signals that were then relayed to the cortex.
This doesn't indicate that patients declared brain dead will all of a sudden wake up—the brains studied here were healthy, and the comas were drug-induced and reversible. But this deeper type of coma could be a better form of neuroprotection than the level of coma that induces a flat EEG reading, the researchers hypothesize. When patients are put in a medically induced coma, which can protect the brain after a serious injury, the lack of brain activity may cause the organ to atrophy, so the greater activity could be beneficial in the long run. "An inactive brain coming out of a prolonged coma may be in worse shape than a brain that has had minimal activity," according to co-author Florin Amzica.
Since this brain activity has only been observed in a single human, though, much more research will be needed to understand the phenomenon.
The study appears in PLOS ONE.