A blinding light. Angelic choruses. Your whole life flashing before your eyes. We all know the kinds of things we mean when we talk about someone having a “near-death experience.”

Scientifically, though, the concept is pretty ill-defined. Ask a neuroscientist, or a critical care physician, for example, what a near-death experience is, or what it means, and you’ll leave them fairly stumped (or fighting amongst themselves). Further research is needed, as they say.

That’s why now, scientists from a wide range of disciplines have published a new consensus statement regarding the study of death. Published in the Annals of the New York Academy of Sciences, the paper is the first-ever peer-reviewed statement on the scientific study of death, and is designed to “provide insights into potential mechanisms, ethical implications, and methodologic considerations for systematic investigation” and “identify issues and controversies” in the research area.

The statement comes at a critical (no pun intended) time, as “death” in the 21st century isn’t the same as death even a hundred years ago.

“[B]eing ‘irreversibly dead’ is technology dependent,” wrote Anders Sandberg, a research fellow at the University of Oxford’s Future of Humanity Institute, back in 2016.

“For a long time, a lack of breathing and pulse were regarded as hallmarks of death, until resuscitation methods improved. Today, drowning victims that suffer extreme hypothermia, lack of oxygen, and lack pulse and breathing for several hours can be revived (with luck and some heavy medical interventions).”

“Even not having a heart isn’t death if you are on the transplant surgeon’s table,” he pointed out.

Sandberg wasn’t involved in the study, but he hits at the heart of the issue: modern medicine has fundamentally changed how we think about death. All of a sudden, we’re learning just how little we know about this most universal part of life.

“Cardiac arrest is not a heart attack,” explained Sam Parnia, director of Critical Care and Resuscitation Research at NYU Grossman School of Medicine, and lead author of the new paper, in a statement.

“[Instead, it] represents the final stage of a disease or event that causes a person to die,” he continued. “The advent of cardiopulmonary resuscitation (CPR) showed us that death is not an absolute state, rather, it’s a process that could potentially be reversed in some people even after it has started.”

In fact, the researchers point out, evidence suggests that neither physiological nor cognitive processes end at the “point of death” – and while scientific studies have so far not been able to prove the reality of near-death experiences, neither can they disprove them.

What is notable is that these experiences – of which there are hundreds of millions recorded from cultures around the world – consistently follow the same themes and narrative arcs. Generally speaking, your average near-death experience involves first feeling separated from your body and having a heightened sense of consciousness and recognition of death; next, a sense of travel to some destination followed by a meaningful and purposeful analysis of your actions, intentions and thoughts towards others throughout your life; then, you’ll feel like you’re in a place that feels like “home”, before finally returning to the real world (and, probably, a lot of very relieved paramedics.)

While that may sound pretty psychedelic, we also know that near-death experiences don’t have a lot in common with hallucinations, illusions, or psychedelic drug induced experiences – though they do often result in the same sort of positive long-term psychological transformation that recent studies have associated with the use of substances like psilocybin.

“What has enabled the scientific study of death is that brain cells do not become irreversibly damaged within minutes of oxygen deprivation when the heart stops,” explained Parnia. “Instead, they ‘die’ over hours of time. This is allowing scientists to objectively study the physiological and mental events that occur in relation to death.”

Modern science has already given us an insight into some of this experience: electroencephalography studies have shown, for instance, the emergence of gamma activity and electrical spikes in relation to death – a phenomenon usually associated with increased awareness. Could that be responsible for the “heightened states of consciousness and recognition of death” felt by those nearing the end? With future research, Parnia and his colleagues hope, we may one day know the answer for sure.

“Few studies have explored what happens when we die in an objective and scientific way,” Parnia said.

“[Our paper] offer[s] intriguing insights into how consciousness exists in humans and may pave the way for further research.”