Spike at the end of the tunnel

Electrical readings from seven patients who died in hospital suggest that the brain undergoes a surge of activity at the moment of death, according to a study just published in the Journal of Palliative Medicine.

Palliative care is a medical approach that aims to make dying patients as comfortable as possible. As part of this, doctors from George Washington University Medical Centre’s intensive care unit were using standard alertness monitors for seven patients that include EEG measurements of the frontal lobes.

The monitors are commercial devices designed to help anaesthetists monitor how ‘awake’ patients are, and they combine the electrical readings from the brain into a single signal that reflects alertness.

For each of the seven patients, the researchers noticed that at the point where blood pressure dropped to zero there was a surge in brain activity. The graph on the right is from one of the patients and shows a typical activity burst.

This is not the first time these have been noticed, but previous reports were single cases and the electrical surges were explained away as due to electrical interference from other sources. In these new cases, the doctors could be pretty confident that previously suggested sources of interference weren’t present.

Instead, they suggest that the surge was due to ‘anoxic depolarisation’ – a process where the lack of oxygen destabilises the electrical balance of the neurons leading to one last cascade of activity.

Now, this is just a case series and the neuroelectrical measures aren’t the best. The researchers encourage more systematic research with appropriate tools, but they do suggest an intriguing hypothesis with regard to ‘near death experiences’:

We speculate that in those patients who suffer cardiac arrest who are successfully revived, they may recall the images and memories triggered by this cascade. We offer this as a potential explanation for the clarity in which many patients have “out of body experiences” when successfully revived from a near death event.

One of the difficulties, of course, is that although ‘near death experiences’ are a well-known phenomenon, we only know about them from people who weren’t really dying (or even from people who were never actually ‘near death’ as one of my favourite studies attests).

Nevertheless, neuroscience studies on the dying are likely to be of increasing interest especially as the debate about what counts as death become more prominent.

Link to DOI entry and summary of study.