There has been a lot of mystery surrounding what is known as near-death experiences or NDEs. The term was coined in psychiatrist Raymond Moody’s popular book Life After Life (1975), in which he detailed people’s testimonials of their NDEs. Moody interviewed 150 people who experienced an NDE as a result of being clinically dead or nearly being clinically dead. It’s worth pointing out that people can experience the subjective effects of an NDE without dying or nearly dying (i.e. through the use of certain drugs).
Based on the subjective reports he collected, Moody claimed there were some common features to the NDE. These included: (1) An overwhelming feeling of peace, (2) An out-of-body experience (OBE), (3) Travelling through a tunnel, (4) Encountering a golden light, (5) Seeing one’s life flash before one’s eyes, and other ‘mystical’ and ‘spiritual’ experiences – feelings of all-encompassing love and timelessness. If someone has a religious background before such an experience, or perhaps interprets the experience in religious terms, they may regard the NDE as a window into a spiritual dimension, heaven, or some sort of ‘after-life’. However, there are more scientifically grounded explanations for why NDEs occur.
Neuroscientist Dean Mobbs, from the University of Cambridge, says, “Many of the phenomena associated with near-death experiences can be biologically explained” in a paper published in Trends in Cognitive Sciences. According to a study by Pim van Lommel and others, 50% of NDE subjects reported an awareness that they were dead. But, as Mobbs points out, people with Cotard or “walking corpse” syndrome also report a feeling that they are dead. This is not due to the soul’s journey out of the physical body but instead is often due to trauma and the associated changes in brain regions such as the parietal cortex and prefrontal cortex. Claiming awareness of being dead is the patient or NDE subject trying to make sense of their strange experience, as opposed to their immaterial soul leaving their physical body.
Out-of-body experiences (OBEs) can be explained in a similar way. OBEs have been reported by people who have experienced sleep paralysis, which can result in vivid hallucinations and the sensation of floating above one’s body. A study published in the Neuroscientist also found that OBEs can be artificially triggered by stimulating the temporoparietal region of the brain. Your perception of your body is ultimately modelled in the brain, so if that function is tampered with, then your experience of your body can be radically altered.
Other hallucinations, such as meeting the deceased, can be explained by the abnormal functioning of dopamine (a neurotransmitter). This affects some people suffering from Parkinson’s disease who report seeing “ghosts”. The experience of seeing your life flash before your eyes might be caused by the stress hormone noradrenaline, which would presumably be released during trauma. Noradrenaline is released by the locus coeruleus region of the brain and this region is also connected to brain regions which mediate memory and emotion (such as the amygdala and hypothalamus).
Karl Jansen’s work into ketamine has established that this dissociative drug can induce many of the phenomena associated with an NDE. Timothy Leary described ketamine use as “experiments in voluntary death”. Ketamine can induce an NDE through the observable effects it has on receptors and neurotransmitters in the brain. The euphoric and mystical aspects of the experience do, therefore, have a physical basis. Mobb also adds that ketamine affects the opioid system, a system which can also become active without the introduction of drugs, such as when an animal is under attack.
The most famous aspect of the NDE is probably travelling through a tunnel towards some beautiful source of light. This “tunnel vision” can be explained, at least in part, by a reduction in blood and oxygen flow to the eye. People have also reported hallucinating tunnels under the influence of drugs, such as ketamine. In a study conducted by Jimo Borjigin, a molecular biologist from the University of Michigan, it was found that electrical activity in the brain can actually increase during cardiac arrest, despite the brain being deprived of oxygen.
In a rather cruel experiment, Borjigin and colleagues used an EGG (which measures the electrical activity of the brain) on rats while the researchers induced cardiac arrest. They found a sharp increase in gamma wave frequency, a type of brain wave responsible for conscious perception. They also found that neurons of the dying rats were firing together in a much more coherent and synchronous way than in their normal, waking state. There was, therefore, a kind of ‘hyper-consciousness’. This could explain why NDE subjects report their experience as being undoubtedly real or a sign of some even truer reality.
In a paper by Birk Engmann, it is argued that the NDE is essentially a psychopathological symptom caused by a malfunction of the brain, brought on by the lack of blood circulation that accompanies physical death. Karl Jansen, the ketamine researcher, also emphasises that hallucinations, by definition, are experiences which seem real to the person. The scientific explanations of the NDE are far more convincing and consistent than explanations involving some sort of afterlife. As Dr Melvin Morse has put it, according to the ‘after-lifer’s’, “the spirit rises out of the body leaving the brain behind, but somehow still incorporating neuronal functions such as sight, hearing, and proprioception.” In other words, their claims are at odds with our current body of evidence which tells us that these functions (and consciousness in general) depend on the physical brain. The reason these functions are retained is that the brain is still active, albeit in a malfunctioning manner.
Rick Strassman in DMT: The Spirit Molecule speculates that the NDE may be caused by an endogenous release of the powerful psychedelic, DMT. Nevertheless, this claim remains in the realm of speculation, since there is no evidence that the human brain has an endogenous supply of DMT, that it is released in massive quantities at the moment of death, or that it is responsible for dreaming. We have ways of explaining NDE phenomena by referring to different mechanisms: stress, trauma, reduction in oxygen and blood flow, drugs, paralysis, mental disorders, dreaming, and so on. We should not resort to supernatural explanations (if they can be called ‘explanations’) which are full of contradictions and depend on testimony and anecdotal reports.