Two of the patients showed a surge of gamma wave activity, considered the fastest brain activity and associated with consciousness. Photograph: Deco/AlamyDeath and dying

People in comas showed ‘conscious-like’ brain activity as they died, study says

‘Potential neuro-signatures of consciousness’ observed in unresponsive patients at time of death, scientists sayHannah Devlin Science correspondent@hannahdevMon 1 May 2023 15.00 EDT

Some recall bright lights at the end of a tunnel, feeling the presence of loved ones or floating above their body after a near-death experience. Now, scientists say they have captured “conscious-like” brain activity in dying patients in findings that give new insights into the process of death.

“How vivid experience can emerge from a dysfunctional brain during the process of dying is a neuroscientific paradox,” said Jimo Borjigin, of the University of Michigan, who led the study. “We saw potential neuro-signatures of consciousness.”

The study used data from four patients who had died in hospital while their brains were being monitored using EEG recordings because they had previously suffered suspected seizures. All four of the patients were comatose and unresponsive and had been deemed beyond medical help. With their families’ permission, life support had been withdrawn and they had subsequently suffered cardiac arrest and died.

The scientists retrospectively analysed the brain activity data in the moments after life support was withdrawn until the patients’ deaths. Upon removal of ventilator support, two of the patients showed an increase in heart rate along with a surge of gamma wave activity, considered the fastest brain activity and associated with consciousness.

This might correspondent to the patients being “internally awakened”, Borjigin suggested.

The activity was detected in the so-called hot zone, an area in the back of the brain linked to conscious brain activity. This area has been correlated with dreaming, visual hallucinations in epilepsy, and altered states of consciousness in other brain studies.

The other two patients did not display the same increase in heart rate or brain activity, according to the study published in the Proceedings of the National Academy of Sciences.

Scientists said it was impossible to know exactly what the brain activity might correspond to as a subjective experience.

“It may be activating internal covert consciousness, bringing out memories of the past, it could be a brain survival mechanism, we don’t know,” said Borjigin.