About the Continuity of Our Consciousness
Pim van Lommel,
Cardiologist, Division of Cardiology, Hospital Rijnstate, PO Box 9555, 6800 TA Arnhem, The Netherlands.
Some people who have survived a life-threatening crisis report an extraordinary experience. Near-death experiences (NDE) occur with increasing frequency because of improved survival rates resulting from modern techniques of resuscitation. The content of NDE and the effects on patients seem similar worldwide, across all cultures and times. The subjective nature and absence of a frame of reference for this experience lead to individual, cultural, and religious factors determining the vocabulary used to describe and interpret the experience. NDE can be defined as the reported memory of the whole of impressions during a special state of consciousness, including a number of special elements such as out-of-body experience, pleasant feelings, seeing a tunnel, a light, deceased relatives, or a life review. Many circumstances are described during which NDE are reported, such as cardiac arrest (clinical death), shock after loss of blood, traumatic brain injury or intra-cerebral haemorrhage, near-drowning or asphyxia, but also in serious diseases not immediately life-threatening. Similar experiences to near-death ones can occur during the terminal phase of illness, and are called deathbed visions. Furthermore, identical experiences, so-called "fear-death" experiences, are mainly reported after situations in which death seemed unavoidable like serious traffic or mountaineering accidents. The NDE is transformational, causing profound changes of life-insight and loss of the fear of death. An NDE seems to be a relatively regularly occurring, and to many physicians an inexplicable phenomenon and hence an ignored result of survival in a critical medical situation.
And should we also consider the possibility of conscious experience when someone in coma has been declared brain dead by physicians, and organ transplantation is about to be started? Recently several books were published in the Netherlands about what patients had experienced in their consciousness during coma following a severe traffic accident, following acute disseminated encephalomyelitis (ADEM), or following complications with cerebral hypertension after surgery for a brain tumour, this last patient being declared brain dead by his neurologist and neurosurgeon, but the family refused to give permission for organ donation. All these patients reported, after regaining consciousness, that they had experienced clear consciousness with memories, emotions, and perception out of and above their body during the period of their coma, also "seeing" nurses, physicians and family in and around the ICU. Does brain death really means death, or is it just the beginning of the process of dying that can last for hours to days, and what happens to consciousness during this period? Should we also consider the possibility that someone who is clinically dead during cardiac arrest can experience consciousness, and even whether there could still be consciousness after someone really has died, when his body is cold? How is consciousness related to the integrity of brain function? Is it possible to gain insight in thisrelationship? In my view the only possible empirical approach to evaluate theories about consciousness is research on NDE, because in studying the several universal elements that are reported during NDE, we get the opportunity to verify all the existing theories about consciousness that have been discussed until now. Consciousness presents temporal as well as everlasting experiences. Is there a start or an end to consciousness?
In this paper I first will discuss some more general aspects of death, and after that I will describe more details from our prospective study on near-death experience in survivors of cardiac arrest in the Netherlands, which was published in the Lancet.1 I also want to comment on similar findings from two prospective studies in survivors of cardiac arrest from the USA2 and from the United Kingdom.3 Finally, I will discuss implications for consciousness studies, and how it could be possible to explain the continuity of our consciousness.
2. ABOUT DEATH
First I want to discuss death. The confrontation with death raises many basic questions, also for physicians. Why are we afraid of death? Are our concepts about death correct? Most of us believethat death is the end of our existence; we believe that it is the end of everything we are. We believe that the death of our body is the end of our identity, the end of our thoughts and memories, that it is the end of our consciousness. Do we have to change our concepts about death, not only based on what has been thought and written about death in human history around the world in many cultures, in many religions, and in all times, but also based on insights from recent scientific research on NDE?
What happens when I am dead? What is death? During our life 500000 cells die each second, each day about 50 billion cells in our body are replaced, resulting in a new body each year. So cell death is totally different from body death when you eventually die. During our life our body changes continuously, each day, each minute, each second. Each year about 98% of our molecules and atoms in our body have been replaced. Each living being is in an unstable balance of two opposing processes of continual disintegration and integration. But no one realizes this constant change. And from where comes the continuity of our continually changing body? Cells are just the building blocks of our body, like the bricks of a house, but who is the architect, who coordinates the building of this house. When someone has died, only mortal remains are left: only matter. But where is the director of the body?What about our consciousness when we die? Is someone his body, or do we "have" a body?
3. SCIENTIFIC RESEARCH ON NEAR-DEATH EXPERIENCE
In 1969 during my rotating internship a patient was successfully resuscitated in the cardiac ward by electrical defibrillation. The patient regained consciousness, and was very, very disappointed. He told me about a tunnel, beautiful colours, a light and beautiful music. I have never forgotten this event, but I did not do anything with it. Years later, in 1976 Raymond Moody first described the so-called "near-death experiences", and only in 1986 I read about these experiences in the book by George Ritchieentitled "Return from Tomorrow," which relates what he experienced during a period of clinical death of 6-minutes duration in 1943 during his medical study.4 After reading his book I started to interview my patients who had survived a cardiac arrest. To my great surprise, within two years about fifty patients told me about their NDE.
My scientific curiosity started to grow, because according to our current medical concepts, it is not possible to experience consciousness during a cardiac arrest, when circulation and breathing have ceased.
Several theories on the origin of an NDE have been proposed. Some think the experience is caused by physiological changes in the brain such as brain cells dying as a result of cerebral anoxia, and possibly also caused by release of endorphins, or NMDA receptor blockade.5 Other theories encompass a psychological reaction to approaching death6 or a combination of such reaction and anoxia.7 But until now there was no prospective, meticulous and scientifically designed study to explain the cause and content of an NDE. All studies had been retrospective and very selective with respect to patients. In retrospective studies 5-30 years can elapse between occurrence of the experience and its investigation, which often prevents accurate assessment of medical and pharmacological factors. We wanted to know if there could be a physiological, pharmacological, psychological or demographic explanation why people experience consciousness during a period of clinical death. The definition of clinical death was used for the period of unconsciousness caused by anoxia of the brain due to the arrest of circulation and breathing that happens during ventricular fibrillation in patients with acute myocardial infarction.
We studied patients who survived cardiac arrest, because this is a well-described life threatening medical situation, where patients will ultimately die from irreversible damage to the brain if cardio-pulmonary resuscitation (CPR) is not initiated within 5 to 10 minutes. It is the closest model of the process of dying.
So, in 1988 we started a prospective study of 344 consecutive survivors of cardiac arrest in ten Dutch hospitals with the aim of investigating the frequency, the cause and the content of an NDE.1 We did a short standardised interview with sufficiently recovered patients within a few days of resuscitation, and asked whether they could remember the period of unconsciousness, and what they recalled. In cases where memories were reported, we coded the experiences according to a weighted core experience index. In this system the depth of the NDE was measured according to the reported elements of the content of the NDE. The more elements were reported, the deeper the experience was and the higher the resulting score was.
Results: 62 patients (18%) reported some recollection of the time of clinical death. Of these patients 41 (12%) had a core experience with a score of 6 or higher, and 21 (6%) had a superficial NDE. In the core group 23 patients (7%) reported a deep or very deep experience with a score of 10 or higher. And 282 patients (82%) had no recollection of the period of cardiac arrest.
In the American prospective study of 116 survivors of cardiac arrest 11 patients (10%) reported an NDE with a score of 6 or higher; the investigators did not specify the number of patients with a superficial NDE with a low score.2 In the British prospective study of 63 survivors of cardiac arrest only 4 patients (6.3%) reported an NDE with a score of 6 or higher, and 3 patients (4.8%) had a superficial NDE, a total of 7 patients (11%) with memories from the period of cardiac arrest.3
In our study about 50% of the patients with an NDE reported awareness of being dead, or had positive emotions, 30% reported moving through a tunnel, had an observation of a celestial landscape, or had a meeting with deceased relatives. About 25% of the patients with an NDE had an out-of-body experience, had communication with "the light," or observed colours, 13% experienced a life review, and 8% experienced a border.
What might distinguish the small percentage of patients who report an NDE from those who do not? We found that neither the duration of cardiac arrest nor the duration of unconsciousness, nor the need for intubation in complicated CPR, nor induced cardiac arrest in electrophysiological stimulation (EPS) had any influence on the frequency of NDE. Neither could we find any relationship between the frequency of NDE and administered drugs, fear of death before the arrest, foreknowledge of NDE, religion or education. An NDE was more frequently reported at ages lower than 60 years, and also by patients who had had more than one CPR during their hospital stay, and by patients who had experienced an NDE previously. Patients with memory defects induced by lengthy CPR reported an NDE less frequently. Good short-term memory seems to be essential for remembering an NDE. Unexpectedly, we found that significantly more patients who had an NDE, especially a deep experience, died within 30 days of CPR (p<0.0001).
We performed a longitudinal study with taped interviews of all late survivors with NDE 2 and 8 years following the cardiac arrest, along with a matched control group of survivors of cardiac arrest who did not report an NDE.1 This study was designed to assess whether the transformation in attitude toward life and death following an NDE is the result of having an NDE or the result of the cardiac arrest itself. In this follow-up research into transformational processes after NDE, we found a significant difference between patients with and without an NDE. The process of transformation took several years to consolidate. Patients with an NDE did not show any fear of death, they strongly believed in an afterlife, and their insight in what is important in life had changed: love and compassion for oneself, for others, and for nature. They now understood the cosmic law that everything one does to others will ultimately be returned to oneself: hatred and violence as well as love and compassion. Remarkably, there was often evidence of increased intuitive feelings. Furthermore, the long lasting transformational effects of an experience that lasts only a few minutes was a surprising and unexpected finding.
Several theories have been proposed to explain NDE. However, in our prospective study we did not show that psychological, physiological or pharmacological factors caused these experiences after cardiac arrest. With a purely physiological explanation such as cerebral anoxia, most patients who had been clinically dead should report an NDE. All 344 patients had been unconscious because of anoxia of the brain resulting from their cardiac arrest. Why should only 18% of the survivors of cardiac arrest report an NDE?
And yet, neurophysiological processes must play some part in NDE, because NDE-like experiences can be induced through electrical "stimulation" of some parts of the cortex in patients with epilepsy,8 with high carbon dioxide levels (hypercarbia)9 and in decreased cerebral perfusion resulting in local cerebral hypoxia, as in rapid acceleration during training of fighter pilots,10 or as in hyperventilation followed by Valsalva maneuver.11 Also NDE-like experiences have been reported after the use of drugs like ketamine,12 LSD,13 or mushrooms.14 These induced experiences can sometimes result in a period of unconsciousness, but can at the same time also consist of out-of-body experiences, perception of sound, light or flashes of recollections from the past. These recollections, however, consist of fragmented and random memories unlike the panoramic life-review that can occur in NDE. Further, transformational processes are rarely reported after induced experiences. Thus, induced experiences are not identical to NDE.
Another theory holds that NDE might be a changing state of consciousness (transcendence, or the theory of continuity), in which memories, identity, and cognition, with emotion, function independently from the unconscious body, and retain the possibility of non-sensory perception. Obviously, consciousness during NDE was experienced independently from the normal body-linked waking consciousness.
With lack of evidence for any other theories for NDE, the concept thus far assumed but never scientifically proven, that consciousness and memories are localized in the brain should be discussed. Traditionally, it has been argued that thoughts or consciousness are produced by large groups of neurons or neuronal networks. How could a clear consciousness outside one's body be experienced at the moment that the brain no longer functions during a period of clinical death, with flat EEG?15 Furthermore, blind people have also described veridical perceptions during out-of-body experiences at the time of their NDE.16 Scientific study of NDE pushes us to the limits of our medical and neurophysiological ideas about the range of human consciousness and relationship of consciousness and memories to the brain.
Also Greyson2 writes in his discussion: "No one physiological or psychological model by itself explains all the common features of NDE. The paradoxical occurrence of heightened, lucid awareness and logical thought processes during a period of impaired cerebral perfusion raises particular perplexing questions for our current understanding of consciousness and its relation to brain function. A clear sensorium and complex perceptual processes during a period of apparent clinical death challenge the concept that consciousness is localized exclusively in the brain." And Parnia and Fenwick3 write in their discussion: "The data suggest that the NDE arises during unconsciousness. This is a surprising conclusion, because when the brain is so dysfunctional that the patient is deeply comatose, the cerebral structures, which underpin subjective experience and memory, must be severely impaired. Complex experiences such as are reported in the NDE should not arise or be retained in memory. Such patients would be expected to have no subjective experience [as was the case in the vast majority of patients who survive cardiac arrest in the three published prospective studies1-3 or at best a confusional state if some brain function is retained. Even if the unconscious brain is flooded by neurotransmitters this should not produce clear, lucid remembered experiences, as those cerebral modules, which generate conscious experience, are impaired by cerebral anoxia. The fact that in a cardiac arrest loss of cortical function precedes the rapid loss of brainstem activity lends further support to this view. An alternative explanation would be that the observed experiences arise during the loss of, or on regaining consciousness. The transition from consciousness to unconsciousness is rapid, with the EEG showing changes within a few seconds, and appearing immediate to the subject. Experiences which occur during the recovery of consciousness are confusional, which these were not". In fact, memory is a very sensitive indicator of brain injury and the length of amnesia before and after unconsciousness is an indicator of the severity of the injury. Therefore, events that occur just prior to or just after loss of consciousness would not be expected to be recalled. And as stated before, in our study1 patients with loss of memory induced by lengthy CPR reported significantly fewer NDE. Good short-term memory seems to be essential for remembering NDE.
4. SOME TYPICAL ELEMENTS OF NDE
Before I discuss in greater detail some neurophysiological aspects of brain functioning during cardiac arrest, I would like to reconsider certain elements of the NDE, like the out-of-body experience, the holographic life review and preview, the encounter with deceased relatives, the return into the body and the disappearance of the fear of death.
4.1. The Out-of-Body Experience
In this experience people have veridical perceptions from a position outside and above their lifeless body. NDEers have the feeling that they have apparently taken off their body like an old coat and to their surprise they appear to have retained their own identity with the possibility of perception, emotions, and a very clear consciousness. This out-of-body experience is scientifically important because doctors, nurses, and relatives can verify the reported perceptions. This is the report of a nurse of a Coronary Care Unit:
During night shift an ambulance brings in a 44-year old cyanotic, comatose man into the coronary care unit. He was found in coma about 30 minutes before in a meadow. When we go to intubate the patient, he turns out to have dentures in his mouth. I remove these upper dentures and put them onto the 'crash cart.' After about an hour and a half the patient has sufficient heart rhythm and blood pressure, but he is still ventilated and intubated, and he is still comatose. He is transferred to the intensive care unit to continue the necessary artificial respiration. Only after more than a week do I meet again with the patient, who is by now back on the cardiac ward. The moment he sees me he says: 'O, that nurse knows where my dentures are.' I am very surprised. Then he elucidates: 'You were there when I was brought into hospital and you took my dentures out of my mouth and put them onto that cart, it had all these bottles on it and there was this sliding drawer underneath, and there you put my teeth.' I was especially amazed because I remembered this happening while the man was in deep coma and in the process of CPR. It appeared that the man had seen himself lying in bed, that he had perceived from above how nurses and doctors had been busy with the CPR. He was also able to describe correctly and in detail the small room in which he had been resuscitated as well as the appearance of those present like myself. He is deeply impressed by his experience and says he is no longer afraid of death.
4.2. The Holographic Life Review
During this life review the subject feels the presence and renewed experience of not only every act but also every thought from one's past life, and one realizes that all of it is an energy field which influences oneself as well as others. All that has been done and thought seems to be significant and stored. Insight is obtained about whether love was given or on the contrary withheld. Because one is connected with the memories, emotions and consciousness of another person, you experience the consequences of your own thoughts, words and actions to that other person at the very moment in the past that they occurred. Hence there is during a life review a connection withthe fields of consciousness of other persons as well as with your own fields of consciousness (interconnectedness). Patients survey their whole life in one glance; time and space do not seem to exist during such an experience. Instantaneously they are where they concentrate upon (non-locality), and they can talk for hours about the content of the life review even though the resuscitation only took minutes. Quotation:
All of my life up till the present seemed to be placed before me in a kind of panoramic, three-dimensional review, and each event seemed to be accompanied by a consciousness of good or evil or with an insight into cause or effect. Not only did I perceive everything from my own viewpoint, but I also knew the thoughts of everyone involved in the event, as if I had their thoughts within me. This meant that I perceived not only what I had done or thought, but even in what way it had influenced others, as if I saw things with all-seeing eyes. And so even your thoughts are apparently not wiped out. And all the time during the review the importance of love was emphasised. Looking back, I cannot say how long this life review and life insight lasted, it may have been long, for every subject came up, but at the same time it seemed just a fraction of a second, because I perceived it all at the same moment. Time and distance seemed not to exist. I was in all places at the same time, and sometimes my attention was drawn to something, and then I would be present there.
Also a preview can be experienced, in which both future images from personal life events (sometimes remembered only later in the shape of "déja vu") as well as more general images from the future occur, even though it must be stressed that these surveyed images should be considered purely as possibilities. And again it seems as if time and space do not exist during this review. Quotation:
I had a nice eye contact, they looked at me full of love, and then I surveyed a great part of my life to come; the care for my children, the terminal illness of my wife, the circumstances I would be mixed up with, in my job and besides. I surveyed it completely; and then I got the feeling that I had to decide now: 'I may stay here, or I have to go back,' but I had to decide now.
4.3. The Encounter with Deceased Relatives
If deceased acquaintances or relatives are encountered in an otherworldly dimension, they are usually recognized by their appearance, while communication is possible through thought transfer. Thus, during an NDE it is also possible to come into contact with fields of consciousness of deceased persons (interconnectedness). Sometimes persons are met whose death was impossible to have known; sometimes persons unknown to them are encountered during an NDE. Quotation:
During my cardiac arrest I had a extensive experience (...) and later I saw, apart from my deceased grandmother, a man who had looked at me lovingly, but whom I did not know. More than 10 years later, at my mother's deathbed, she confessed to me that I had been born out of an extramarital relationship, my father being a Jewish man who had been deported and killed during the second World War, and my mother showed me his picture. The unknown man that I had seen more than 10 years before during my NDE turned out to be my biological father.
4.4. The Return into the Body
Some patients can describe how they returned into their body, mostly through the top of the head, after they had come to understand through wordless communication with a Being of Light or a deceased relative that "it wasn't their time yet" or that "they still had a task to fulfil." The conscious return into the body is experienced as something very oppressive. They regain consciousness in their body and realize that they are "locked up" in their body, meaning again all the pain and restriction of their disease. They also realize that a part of their consciousness with deep knowledge and understanding as well as the feeling of unconditional love and acceptance have been taken away from them again. Quotation:
And when I regained consciousness in my body, it was so terrible, so terrible... that experience was so beautiful, I never would have liked to come back, I wanted to stay there... and still I came back. And from that moment on it was a very difficult experience to live my life again in my body, with all the limitations I felt in that period.
4.5. The Disappearance of Fear of Death
Nearly all people who have experienced an NDE lose their fear of death. This is due to the realization that there is a continuation of consciousness, even when you have been declared dead by bystanders or even by doctors. You are separated from the lifeless body, retaining the ability of perception. Quotation:
It is outside my domain to discuss something that can only be proven by death. For me, however, the experience was decisive in convincing me that consciousness lives on beyond the grave. Death was not death, but another form of life.
This experience is a blessing for me, for now I know for sure that body and mind are separated, and that there is life after death.
Following an NDE people know of the continuity of their consciousness, retaining all thoughts and past events. And this insight causes exactly their process of transformation and the loss of fear of death. Man appears to be more than just a body.
5. NEUROPHYSIOLOGY IN CARDIAC ARREST
All these elements of an NDE were experienced during the period of cardiac arrest, during the period of apparent unconsciousness, during the period of clinical death! But how is it possible to explain these experiences during the period of temporary loss of all functions of the brain due to acute pancerebral ischemia?
We know that patients with cardiac arrest are unconscious within seconds. But how do we know that the electroencephalogram (EEG) is flat in those patients, and how can we study this? Complete cessation of cerebral circulation is found in cardiac arrest due to ventricular fibrillation (VF) during threshold testing at implantation of internal defibrillators. This complete cerebral ischemic model can be used to study the result of anoxia of the brain.
In VF complete cardiac arrest occurs, with complete cessation of cerebral flow, resulting in acute pancerebral anoxia. The middle cerebral artery blood flow, Vmca, which is a reliable trend monitor of the cerebral blood flow, decreases to 0 cm/sec immediately after the induction of VF.17 Through many studies in both human and animal models, cerebral function has been shown to be severely compromised during cardiac arrest, and electrical activity in both cerebral cortex and the deeper structures of the brain has been shown to be absent after a very short period of time. Monitoring of the electrical activity of the cortex (EEG) has shown that ischemia produces a decrease of power in fast activity and in delta activity and an increase of slow delta I activity, sometimes also an increase in amplitude of theta activity, progressively and ultimately declining to isoelectricity. More often initial slowing and attenuation of the EEG waves is the first sign of cerebral ischemia. The first ischemic changes in the EEG are detected an average of 6.5 seconds after circulatory arrest. With prolongation of the cerebral ischemia, progression to isoelectricity occurs within 10 to 20 (mean 15) seconds from the onset of cardiac arrest.18-21
After defibrillation the Vmca, measured by transcranial Doppler technique, returns rapidly within 1-5 seconds after a cardiac arrest of short duration. However, in the case of a prolonged cardiac arrest of more than 37 seconds, the Vmca shows an initial overshoot upon reperfusion, a transient global hyperaemia, followed by a significant decrease in cerebral blood flow up to 50% or less of normal.22 This results also in an initial overshoot of cerebral oxygen uptake (hyperoxia) with a fast decrease in cerebral oxygen uptake to borderline values for a considerable time due to delayed hypoperfusion.18,22 In the case of a prolonged cardiac arrest the EEG recovery also takes more time, and normal EEG activity may not return for many minutes to hours after cardiac function has been restored, depending on the duration of the cardiac arrest, despite maintenance of adequate blood pressure during the recovery phase. Additionally, EEG recovery underestimates the metabolic recovery of the brain, and cerebral oxygen uptake may be depressed for a considerable time after restoration of circulation.18 In acute myocardial infarction the duration of cardiac arrest (VF) in the Coronary Care Unit (CCU) is usually 60-120 seconds, on the cardiac ward 2-5 minutes, and in out-of-hospital arrest it usually exceeds 5-10 minutes. Only during threshold testing of internal defibrillators or during electrophysiological stimulation studies will the duration of cardiac arrest rarely exceed 30-60 seconds.
Anoxia causes loss of function of our cell systems. However, in anoxia of only some minute's duration this loss may be transient; in prolonged anoxia cell death occurs, with permanent functional loss. During an embolic event a small clot obstructs the blood flow in a small vessel of the cortex, resulting in anoxia of that part of the brain, with loss of electrical activity. This results in a functional loss of the cortex like hemiplegia or aphasia. When the clot is dissolved or broken down within several minutes the lost cortical function is restored. This is called a transient ischemic attack (TIA). However, when the clot obstructs the cerebral vessel for minutes to hours, it will result in neuronal cell death, with a permanent loss of function of this part of the brain, with persistent hemiplegia or aphasia, and the diagnosis of cerebrovascular accident (CVA) is made. So transient anoxia results in transient loss of function.
In cardiac arrest global anoxia of the brain occurs within seconds. Timely and adequate CPR reverses this functional loss of the brain, because definitive damage of the brain cells, resulting in cell death, has been prevented. Long lasting anoxia, caused by cessation of blood flow to the brain for more than 5-10 minutes, results in irreversible damage and extensive cell death in the brain. This is called brain death, and most patients will ultimately die.