The iconic image of a tunnel of light during near-death experiences, often portrayed in movies and literature or shared in personal accounts, is frequently linked to visions of the afterlife. Nevertheless, there might be a scientific basis for these occurrences and other related experiences.

As death approaches, the body undergoes swift and profound changes, notably a reduction in vital functions. This includes a slower heart rate, leading to diminished oxygen flow throughout the body, affecting the brain in particular. Other physical alterations can include a decrease in body temperature and irregular, shallow breathing patterns.

It’s not only the external organs that experience these shifts—the brain also undergoes major transformations. Research from the University of Michigan indicates that the brains of individuals nearing death exhibit a substantial surge in activity.

In the study, which observed four patients being taken off life support, two showed a spike in brain activity just before death. Fascinatingly, this activity mirrored the processes found in conscious thought.

This cerebral activity is driven by gamma waves, or brain waves, with one participant exhibiting a three-hundred-fold increase. Jimo Borjigin, a researcher from the University of Michigan, proposed the existence of a ‘covert consciousness’ that may become active shortly before death.

Professor Borjigin elaborated that those nearing death could recall “seeing or hearing things, having an out-of-body experience, or sensing movement as if they are flying.” She added, “I believe we have potentially identified or discovered fundamental anatomical steps to the neurosignatures of covert consciousness.”

“We’d like to be able to study human subjects under less devastating circumstances, where the patients are known to be able to survive and then tell the story where they can correlate their brain signature with a subjective experience.”

In relation to serotonin and hallucinations, Professor Borjigin referred to a previous study she conducted on rats in a lab. She observed a surge in serotonin in the brain just moments before death.

This chemical, typically found in excessive amounts in psychiatric disorders, could also trigger hallucinations. However, it remains unclear whether rats experience similar brain chemistry to humans.

Despite this, she drew from a previous PNAS study, which discovered that the brains of dying rats emitted a similar surge of gamma waves during heart attacks. In a 2013 paper, her team penned: “These data demonstrate that the mammalian brain can, albeit paradoxically, generate neural correlates of heightened conscious processing at near-death.”

Research unveiled in the Journal of the Missouri State Medical Association also scrutinises the role of brain consciousness and its influence on near-death experiences. However, it emphasises that there is still a great deal that researchers don’t comprehend about the brain’s relationship with consciousness, as well as its impact on near-death experiences.