In 2016, an 87-year-old man went to the emergency room at Vancouver General Hospital after falling down. A CT scan showed that his brain was bleeding, and he needed surgery. After the operation, the man was stable for two days, but then he started to decline and have seizures.

Because of the seizures, his doctors measured the electrical signals from his brain using an electroencephalogram, or EEG. While the electrodes were on his head, the man had a heart attack and died.

Most recently, in 2021, a study looked at data from patients that died from heart attacks, who had also been undergoing standard EEG monitoring in an ICU. Of 19 patients who died a cardiac death, 11 had EEG activity following permanent cessation of the electrical or pump function of the heart, they reported. Jan Claassen, the senior author on that paper and a neurologist at Columbia University, said that they had one patient out of 19 who showed EEG activity briefly after blood flow to the brain stopped.

This has been seen in animals too. In a study from 2013, George Mashour, an anesthesiologist at the University of Michigan, and first author Jimo Borjigin looked for this brain activity in rats. They implanted electrodes into the brains of nine anesthetized rats, and then killed them. In the moment just after cardiac death, there was a surge of high-frequency brain activity.

They found that the surge of electrical activity wasn’t just the brain going “haywire” before death, Mashour said. The brain activity was coordinated, and in a specific higher wave frequency: the gamma bandwidth.  

Read the full article at Vice.