NEAR-DEATH experiences are often reported by patients who have been exposed to severe trauma, such as cardiac arrest, and who have been close to death but subsequently resuscitated. Features of the NDE include buzzing noises, a deep sense of peace, passing through a tunnel into a bright light and meeting people who have died combined with a strong sense of the validity of the experience.
Another commonly reported aspect of the NDE is an out of body experience (OBE) in which the body is viewed from above and general surroundings can be observed. Some patients claim to have seen surgeons operate on them and to have heard conversations taking place. Medical personnel have occasionally supported the latter claims and verified their accuracy.
Many explanations have been posited for the NDE, but it is still not fully understood. For many it is an indication of the reality of an afterlife, and those who have had the experience often report an increased appreciation for life and a decreased fear of death.
NDEs and OBEs raise interesting questions with regard to consciousness and the relationship between the brain and the mind. Can the mind (or the spirit, according to some) objectively detach from the body while retaining apparently normal neurological functions such as vision, taste, smell and comprehension, or are these experiences the consequence of dreams, hallucinations or other processes precipitated by trauma or associated factors?
Dr Karl Jansen, a psychiatrist working at the Maudsley Hospital, London, has proposed an explanatory model based primarily on the effect of particular anaesthetics on brain function. Ketamine, for instance, is a short-acting hallucinogenic, dissociative anaesthetic that can induce an NDE in normal subjects. When used medically, it is usually co-administered with benzodiazepines or other sedatives to prevent the occurrence of dissociative experiences such as OBEs which are referred to as “psychic emergence reactions”.
With regard to the reference above to patients reporting conversations occurring in the operating theatre, Jansen cites research indicating that “ketamine can permit sufficient sensory input to allow accounts of procedures during which the patient appeared wholly unconscious”.
Dr G M Woerlee, an Australian anaesthesiologist working in the Netherlands, has proposed a different model to account for the tunnel and light phenomena reported as accompanying NDEs. He refers primarily to oxygen starvation and its effects on vision. He explains that with decreased oxygen levels and increased sympathetic nervous system activity in dying patients, the pupils are maximally dilated which results in a sensation of extreme brightness. Those in attendance (nurses, surgeons, etc) appear as bright, blurred forms and this may account for the regular reports of the presence of dead people or angelic beings.
It is suggested that the tunnel effect is due to peripheral vision being affected initially by oxygen depletion, followed by the central parts of the retina, resulting in a narrowing of the visual field. A similar tunnelling phenomenon is often experienced during fainting episodes when blood flow to the head is temporarily disrupted.
An interesting set of experiments is under way across 25 hospitals in the United States and the UK under the direction of Dr Sam Parnia, a consultant in critical care medicine working at Southhampton University. He is investigating whether reports of OBEs reflect genuine observations.
The initial phase of the investigation will have pictures placed on special shelves installed in operating theatres and intensive-care units that are only visible if observed from above and close to ceiling level. It is intended that 1,500 cardiac arrest survivors will be interviewed to ascertain if any actually saw the pictures during OBEs.
Psychologists, philosophers, neurologists and other professionals are working hard to understand the nature of consciousness and the mind-brain issue. The generally accepted view is that consciousness is an emergent property of our physiology. Given the complexity of the human brain and its vast electrical and chemical interconnections, the potential for emergent phenomena is essentially incalculable.
My own view is that the phenomenon of emergence is sufficient to account for NDEs and OBEs, and there is no need to refer to spiritual or supernatural variables. Obviously a lot of detail needs to be filled in, but the models proposed by Jansen, Woerlee and others to whom I have not referred, provide good starting points for continued investigation.
I doubt if the subjects in Parnia’s experiments will report back accurately on the content of his pictures. The results should emerge in 2012, so we must wait and see. As always in science, the data will decide.
Paul O’Donoghue is a founder member of the Irish Skeptics Society