"Flat line was the deepest known form of coma," said study researcher Florin Amzica, neurophysiologist at Université de Montréal.
The new study shows "there's a deeper form of coma that goes beyond the flat line, and during this state of very deep coma, cortical activity revives," Amzica said. He noted the findings apply to patients in a medically induced coma with healthy brains that are receiving blood and oxygen. The conclusions may not extend to cases of comatose patients who have suffered major brain damage, he said.
The newly discovered coma state is characterized by electrical waves called Nu-complexes that are unlike other waveforms generated by the brain during known coma states, sleep or wakefulness. These waves originate in a deep brain region called the hippocampus, and then spread across the cortex (the brain's outermost layer), according to the study.
The new findings came from a serendipitous observation in a patient who was in a deep coma and receiving powerful epilepsy medication required to control his convulsions. EEG recordings of his brain's electrical activity showed peculiar and unexplainable waveforms, the researchers said. (10 Things You Didn't Know About the Brain)