What a Flat EEG Does and Doesn't Mean

Cardiac arrest is not brain death, and the difference matters

A reader told me I hadn’t been clear enough about something: a cardiac arrest is not the same as brain death. They were right, and I’d rather be corrected in public than be wrong in private. So here is what we know, and what it means for things I’ve said before.

What happens to the brain in cardiac arrest with a flat EEG

When the heart stops, blood stops reaching the brain. Within a few seconds, the electrical signal at the scalp begins to slow. By about 10 to 20 seconds, it’s flat. That is what doctors mean by a flat EEG.

But flat on the scalp does not mean dead. Brain cells can survive for minutes without blood, which is the only reason people can be brought back at all. And a scalp EEG mostly picks up activity near the surface of the cortex. It can’t see deep structures well. So the careful claim is that organised electrical activity at the surface stops. “No brain activity” goes further than the evidence does, and I’ve been guilty of that kind of loose wording myself.

Here is the awkward part for my own side. Pim van Lommel’s 2001 Lancet study followed 344 patients through 509 successful resuscitations. Sixty-two of them (18%) remembered something from the time they were clinically dead. That is a real finding, and the study was well designed for counting how often it happens. But it did not record an EEG on those patients. It argued from earlier research that the signal would have gone flat within seconds. That is a reasonable argument. It is not a measurement, and I should have said so.

The dying brain isn’t quiet

Now for something that surprised a lot of people, including me. In 2013, Jimo Borjigin’s lab at the University of Michigan stopped the hearts of rats. In the first 30 seconds and before the signal went flat, the rats’ brains showed a burst of fast, highly organised gamma activity.

In 2023. her team reported a similar burst in two of four comatose patients after life support was withdrawn. The authors were careful. They said they couldn’t rule out that it was a pathological process with nothing to do with conscious experience.

This cuts both ways, and I’m not going to pretend otherwise. It shows the dying brain is not simply switched off, so a vivid experience in those first seconds is not a mystery on its own.

A materialist can point to it and say the brain is putting on a final show. But it also shows that nobody has yet connected such a burst to what patients actually report. Two of four patients is a small number, and a burst is not a story. Neither camp gets to claim this one.

The timing problem

This is the hardest problem in the whole debate, and it’s the one I’d put to anyone making strong claims, myself included. People tell us their experience after they wake up. They can’t tell us when in the sequence it happened. It could have been in the seconds as consciousness faded. It could have been during the burst. It could have been during CPR, or as they were coming round. CPR itself can bring some people back to a kind of awareness. Without a timestamp, a vivid memory cannot be placed inside the flat stretch.

That is why a beautiful account of floating above the room, however sincere and however life changing, does not settle anything on its own. The experience is real to the person. The question is when it happened, and memory has no clock.

So what can I fairly say? Some people report clear, structured experiences around cardiac arrest, and many come away changed. That is well documented. Whether any of it happened while the brain showed no organised activity has not been shown. The only way to settle it is to tie something in the report to an event at a known time. That is what the next post is about.

Kathy Postelle Rixon is Chair of The Philosophical Society: Oxford, an independent researcher in consciousness studies, and a shamanic practitioner of more than forty years, working in Q’ero, Norse and Celtic traditions. You can contact her at kathy@magicinharmony.com or visit her website at www.magicinharmony.com.