AI-generated image created by Prof. Blundell

Near-death experiences (NDEs) have captivated humanity for centuries. Individuals who have come close to death often recount vivid and surreal experiences that include out-of-body sensations, encounters with deceased loved ones, seeing a tunnel of light or feeling a profound sense of peace. Despite their mystical quality, scientists are increasingly convinced that NDEs can be explained, at least in part, by biochemistry. By examining what happens in the brain during moments of extreme stress, trauma or oxygen deprivation, researchers are beginning to demystify the origins of these experiences. This article explores the biochemical processes that may underpin NDEs, offering insight into why they occur and how they shape our understanding of consciousness.

Understanding NDEs

The first modern study of NDEs began in the 1970s when psychiatrist Dr Raymond Moody coined the term in his book "Life After Life". He documented hundreds of cases where individuals described similar sensations after coming close to death. These experiences often follow a familiar pattern: a feeling of leaving the body, travelling through a tunnel, meeting spiritual beings, and sometimes reviewing one's life in vivid detail. NDEs are not confined to one culture or belief system. They have been reported across the world and throughout history, yet their commonality suggests a potential biological basis.

The brain's response to trauma

To understand the biochemical reasons behind NDEs, we must first explore what happens to the brain during trauma or extreme stress. The brain is an extraordinarily complex organ, highly sensitive to changes in its environment. When the body is under duress - whether from cardiac arrest, severe blood loss or asphyxiation - the brain experiences a sharp reduction in oxygen and glucose supply, both of which are critical for its functioning.

Hypoxia or oxygen deprivation, is particularly damaging to the brain. Neurons, the brain cells responsible for transmitting information, begin to malfunction within seconds of oxygen depletion. However, before neurons die, they enter a hyperactive state, releasing a flood of neurotransmitters in an effort to communicate. This neurotransmitter surge could potentially trigger the extraordinary sensations reported in NDEs.

The role of neurotransmitters

Neurotransmitters are chemical messengers in the brain that regulate everything from mood to perception. During a near-death event, certain neurotransmitters are released in large quantities, which may help explain the intense sensations that people describe.

Glutamate: Glutamate is the brain's primary excitatory neurotransmitter, responsible for stimulating neurons and facilitating brain activity. During oxygen deprivation, the brain releases large amounts of glutamate. This glutamate flood can overstimulate neurons, leading to an altered state of consciousness. Studies have suggested that glutamate-induced excitotoxicity could explain the heightened perception, out-of-body experiences and even life reviews that occur during NDEs.

Endorphins: Endorphins are the brain's natural painkillers, released in response to stress or trauma. In near-death situations, the brain floods the body with endorphins, which not only help to numb physical pain but also create a sense of euphoria. Many people who experience NDEs report feeling calm, peaceful, and detached from their physical body - emotions that can be attributed to this endorphin rush.

Serotonin: Serotonin is a neurotransmitter that regulates mood, and its release during moments of crisis may contribute to the surreal and emotionally profound nature of NDEs. Some research suggests that high levels of serotonin during trauma can lead to vivid visual hallucinations, a key feature in NDEs, such as seeing tunnels of light or encountering deceased loved ones.

Norepinephrine and dopamine: These neurotransmitters play critical roles in the brain's stress response. Norepinephrine heightens awareness and prepares the body for the "fight or flight" response, while dopamine is associated with feelings of reward and pleasure. During a near-death event, a flood of dopamine and norepinephrine may create a heightened state of arousal and sensory perception, leading to the vivid and emotionally charged experiences reported by many NDE survivors.

Ketamine and NDEs: A clue from anaesthesia

Further insight into the biochemistry of NDEs comes from studies on ketamine, a dissociative anaesthetic used in both medical and recreational contexts. In low doses, ketamine can induce sensations strikingly similar to those described in NDEs, including out-of-body experiences, intense visual hallucinations and feelings of peace and detachment.

Ketamine works by blocking NMDA receptors in the brain, which are responsible for regulating glutamate. By inhibiting these receptors, ketamine produces a state of dissociation from the physical body. Some researchers believe that a similar process may occur during NDEs, as the brain's response to trauma mimics the effects of ketamine, leading to altered consciousness.

Studies have shown that patients who have been administered ketamine report experiences nearly identical to those of NDEs, including tunnel vision, meeting spiritual entities and a sense of transcendence. This has led some scientists to hypothesise that the brain may naturally release chemicals similar to ketamine during moments of extreme stress, explaining the near-universal nature of NDEs across cultures.

DMT: The 'Spirit Molecule' and its role in NDEs

Another compound that has garnered attention in discussions of NDEs is Dimethyltryptamine (DMT), a powerful hallucinogen found in certain plants and produced naturally in small quantities by the human brain. Some researchers have suggested that DMT, often referred to as the "spirit molecule", may play a role in near-death experiences.

Dr Rick Strassman, who conducted groundbreaking research on DMT in the 1990s, noted that the effects of DMT often mirror those of NDEs. Subjects administered DMT reported being transported to otherworldly realms, encountering beings of light and experiencing a profound sense of peace and interconnectedness - experiences strikingly similar to those described by NDE survivors.

While the exact function of naturally occurring DMT in the human brain remains unclear, some hypothesise that the brain may release a surge of DMT during moments of extreme stress, such as a near-death experience. This could explain the vivid and transcendental nature of many NDEs.

The temporal lobe: a gateway to the mystical?

The temporal lobe, a region of the brain located near the temples, is also thought to play a crucial role in NDEs. This part of the brain is responsible for processing sensory information, emotions and memory, making it a prime candidate for explaining the life reviews and heightened perceptions often reported during NDEs.

Electrical stimulation of the temporal lobe has been shown to produce mystical experiences, including a sense of detachment from the physical body and encounters with spiritual beings. Some scientists believe that during moments of trauma, abnormal electrical activity in the temporal lobe could trigger these sensations, providing a neurological basis for many of the elements found in NDEs.

In fact, studies have shown that patients with temporal lobe epilepsy sometimes experience events similar to NDEs during seizures. These individuals often report feelings of déjà vu, vivid hallucinations and intense emotional experiences - phenomena that closely resemble those described by NDE survivors.

A burst of activity at death

Recent research has provided further insight into the brain's activity at the moment of death. In a 2013 study conducted on rats, scientists discovered that the brain experiences a sudden burst of activity in the moments following cardiac arrest. This surge of brain activity, which lasted for about 30 seconds, was characterised by highly synchronised neural firing, similar to the patterns seen during conscious states.

Although this study was conducted on animals, it raises intriguing questions about what happens in the human brain during the dying process. Could this final burst of activity be responsible for the heightened perceptions and vivid experiences associated with NDEs? Some researchers believe that this brain surge may be the brain's last attempt to make sense of its environment, producing the extraordinary experiences reported by many near-death survivors.

Demystifying the near-death experience

While NDEs have long been shrouded in mystery, advances in neuroscience and biochemistry are beginning to shed light on the biological processes that may underlie these phenomena. By examining the brain's response to trauma, the role of neurotransmitters, and the influence of chemicals like DMT and ketamine, scientists are piecing together a biochemical explanation for NDEs.

Though much about NDEs remains unknown, one thing is clear: these experiences offer profound insights into the nature of consciousness, perception and the brain's incredible capacity to adapt to extreme situations. Whether viewed as evidence of an afterlife or a biological response to trauma, NDEs continue to fascinate both scientists and the public alike, providing a unique window into the mysteries of the human mind.

Renald Blundell is a biochemist and biotechnologist with a special interest in Natural and Alternative Medicine. He is a professor at the Faculty of Medicine and Surgery, University of Malta.