Death is one of life's greatest mysteries, but new research may shed light on what happens when we pass to the other side.
Imagine reliving your entire life in the space of mere seconds. Like a flash of lightning, you watch all the memorable moments you lived through. This process, known as 'life recall', can be similar to what it's like to have a near-death experience. What happens inside your brain during these experiences and after death are questions that have puzzled neuroscientists for centuries.
There's long been the school of thought that life flashes before one's eyes in the face of death, a notion corroborated by multiple reports from people on the brink of passing. Over the years, people have reported witnessing multiple scenes from their past during split-second emergencies, with the first report emerging well over a century ago. In 1892, a Swiss geologist named Albert Heim fell from a rock face while mountain climbing. He later described the accident, "as if on a distant stage, my whole past life [was] playing itself out in numerous scenes".
In July 2005, a woman named Gill Hicks was sitting near one of the bombs that exploded on the London Underground. She survived the attack, but had been on the cusp of death. In a TedTalk in 2016, Hicks recounted what it was like to be on the precipice of passing: "My life was flashing before my eyes, flickering through every scene, every happy and sad moment, everything I have ever done, said, experienced."
Now, US neuroscientists who recorded the activity of a dying human brain say that as we die, our brainwave patterns are similar to those that occur during dreaming, recalling memories and meditation - and our brains may remain active and coordinated during, and even after, we pass.
A new study on these findings, published in Frontiers in Aging Neuroscience this week, brings new insight into a possible organisational role of the brain during death and suggests an explanation for vivid life recall in near-death experiences.
When an 87-year-old patient developed epilepsy, Dr Raul Vicente of the University of Tartu in Estonia and his colleagues used continuous electroencephalography (EEG) to detect the seizures and treat the patient. During these recordings, the patient suffered a heart attack and passed away. This unexpected event allowed the scientists to record the activity of a dying human brain for the first time ever.
"We measured 900 seconds [15 minutes] of brain activity around the time of death and set a specific focus to investigate what happened in the 30 seconds before and after the heart stopped beating," said Dr Ajmal Zemmar, a neurosurgeon at the University of Louisville in Kentucky, US who organised the study.
"Just before and after the heart stopped working, we saw changes in a specific band of neural oscillations, so-called gamma oscillations, but also in others such as delta, theta, alpha and beta oscillations."
Brain oscillations, more commonly known as 'brainwaves', are patterns of rhythmic brain activity normally present in living human brains. The different types of oscillations, including gamma, are involved in high-cognitive functions such as concentrating, dreaming, meditation, memory retrieval, information processing and conscious perception, just like those associated with memory flashbacks.
The researchers say the brainwaves they recorded in the 30 seconds prior to and after the patient's heart stopped beating are usually involved in these high-cognitive functions, and could be a literal example of someone's life flashing before their eyes.
"Through generating oscillations involved in memory retrieval, the brain may be playing a last recall of important life events just before we die, similar to the ones reported in near-death experiences," Zemmar said.
"These findings challenge our understanding of when exactly life ends and generate important subsequent questions, such as those related to the timing of organ donation."
While this study is the first of its kind to measure a human's live brain activity during the process of dying, similar changes in gamma oscillations have been previously observed in rats kept in controlled environments. This indicates that during death, it's possible the brain organises and executes a biological response that could be seen across various species.
However, these findings are based on a single case and stem from the brain of a patient who had suffered injury, seizures and swelling, which complicates the interpretation of the data, the researchers note.
Nonetheless, Zemmar plans to investigate more cases and says the results are a source of hope.
"As a neurosurgeon, I deal with loss at times. It is indescribably difficult to deliver the news of death to distraught family members," he said.
"Something we may learn from this research is that although our loved ones have their eyes closed and are ready to leave us to rest, their brains may be replaying some of the nicest moments they experienced in their lives."
