Sep 19 2008

Studying Near Death Experiences

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Near death experiences (NDEs) have been a favorite topic for the paranormal crowd for some time. If one could prove that consciousness survives the physical death of the body that would go a long way to opening the door to a wide range of paranormal claims. NDEs often occur in the medical setting, and this is partly why a team of doctors from the UK and USA are planning a rigorous study of NDEs.

That NDEs occur is not controversial – many people report remembering experiences around the time of cardiac arrest from which they were revived. Typical experiences include a sense of floating outside of one’s body, even looking down upon oneself and the events going on. Some people report a bright light, and others report “passing over” and being greeted by deceased loved-ones. The experience is often peaceful or euphoric, which contrasts to the way people feel when they eventually wake up. Surviving a cardiac arrest takes its toll and is not a pleasant experience.

The question is not whether or not people have such experiences – the question is how to interpret them. Just as even the most rigorous skeptic does not question that people see UFOs, but rather what the UFOs likely are.

The burden of proof for anyone claiming that NDEs are evidence for the survival of the self beyond the physical function of the brain is to rule out other more prosaic explanations. This burden has not been met.

Neuroscientists are piecing together plausible explanations for each of the components of the NDE. The sensation of floating outside one’s body can be reliably induced by suppressing that part of the brain that makes us feel as if we possess our bodies. The experience is identical to that reported by those who have had an NDE. This experience can be replicated by drugs or magnetic stimulation. There are even reports (I have had one such patient) of people who have a typical NDE experience during seizures. The bright light can be explained as a function of hypoxia (relative lack of oxygen) either to the retina or the visual cortex. Any everything else is simply the culturally appropriate hallucinations of a hypoxic brain.

Critics of such explanation try to argue that during the experience the brain is not active, therefore the brain cannot be the source of the experiences. There are two problems with this argument. First, it has not been established that the brain is not sufficiently active to generate experiences. In all cases people survived the experience (by definition) to report what they remember. That means the brain did not go entirely without oxygen for very long or otherwise it would have been catastrophically damaged. During cardiopulmonary resuscitation (CPR) the cardiac output is about 20-25% normal – enough to delay damage to tissues. So the brain is getting some oxygen. Not enough to be conscious, but enough to have some function – perhaps generate a dream-like hallucination or out-of-body experience.

Second, the argument assumes without justification that the memories reported by those who survive CPR and have an NDE were formed during the CPR or when they were unconscious. It is more likely that some or all of those memories formed when the person was waking up adn their sense of time is as distorted as all their brain function. Unlike in the movies, people do not wake up fully conscious and lucid after having their heart restarted. After minutes of CPR the brain has taken a hit due to the hypoxia. People typically wake from this event slowly – taking hours or even days, depending on the duration and quality of the CPR. They will necessarily pass through a phase where they are what is called encephalopathic (their brain is functioning but not well), which is a type of delirium. It is common to have bizarre thoughts and perceptions, hallucination, and illusions during this period.

When patients then fully wake up to report their experiences, all they have is their memories, which includes the memories of the transition period from unconscious, through a delirious period, and to fully conscious.  They have no way of knowing when those memories formed.

The only way to definitively distinguish between memories formed during CPR and those formed during the period of encephalopathy is for the memories to contain specific details that could only have been obtained during the CPR. This claim is often made, but either there is a lack of compelling documentation, or the details are too vague to be definitive. People describing a typical CPR experience, for example, is not specific. Sometimes people after a NDE will claim to recognize the nurse or doctor who worked on them, but they may just be attaching those memories to people they encountered before or after the experience.

This brings us to the proposed study. What Dr. Sam Parnia, the head of the study, wants to do is to place a sign with specific information on it on top of shelving so that it can only be viewed from the ceiling. These will be placed in intensive care units and emergency departments. Patients who experience cardiac arrest and survive will be systematically interviewed at the participating hospitals and asked if they had any NDE and also be asked if they were able to identify the signs on top of the shelves. Assuming no cheating goes on, the only way such patients could have obtained the information would be if there experience of floating above their bodies was an actual experience interacting with the real physical world.

The study is likely to take 2-3 years so we won’t have results for a while.

The purpose of the study explicitly recognizes that the claim that NDEs are a non-physical experience of consciousness requires this type of evidence to distinguish it from a mere hallucination of a hypoxic or encephalopathic brain.  I predict that the study will be negative, and that proponents of NDEs as a spiritual experience will be unmoved by this evidence.

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