By Stuart Hameroff, MD and Deepak Chopra, MD
The idea that conscious awareness can exist after death, generally referred to as the 'soul', has been inherent in Eastern and Western religions for thousands of years. In addition to spiritual accounts, innumerable subjective reports of conscious awareness seemingly separated from the subject's brain and physical body occur in conjunction with so-called near death experiences (NDEs) in patients resuscitated after cardiac arrest (1,2). Such patients describe remarkably consistent phenomenology including a white light, being in a tunnel, serenity, deceased loved ones, life review and, in some cases, floating out of the body (out-of-body experiences - OBEs). Comparable experiences have been reported in various types of meditative and altered states, traumatic psychological events, or seemingly without cause. A Gallup poll estimated some 10 million Americans have reported NDEs/OBEs (3). The drug ketamine, used as a 'dissociative' anesthetic, can produce subjective reports of conscious awareness outside the body (4), as can various other psychoactive drugs.
Modern science is unable to explain NDEs/OBEs, and ignores and derides such reports as unscientific folly or hallucination. But modern science can't explain normal, in-the-brain consciousness. Despite detailed understanding of neuronal firings and synaptic transmissions mediating non-conscious cognitive functions, there is no accounting for conscious awareness, free will or 'qualia'- the essence of experienced perceptions, like the redness, texture and fragrance of a rose. Philosopher David Chalmers refers to this as the 'hard problem' - explaining qualia and the subjective nature of feelings, awareness, and phenomenal experience - our 'inner life'. Unable to explain consciousness in the brain, it is easy to see why conventional science ignores out-of-body, or after-death consciousness, rejecting even the possibility of their occurrence.
Science can measure brain electrical activity known to correlate with consciousness, for example high frequency synchronized electroencephalography (EEG) in the gamma range ('gamma synchrony'). Monitors able to measure and process EEG and detect gamma synchrony and other correlates of consciousness have been developed for use during anesthesia to provide an indicator of depth of anesthesia and prevent intra-operative awareness, i.e. to avoid patients being conscious when they are supposed to be anesthetized and unconscious. The 'BIS' monitor (Aspect Medical Systems, Newton MA) records and processes frontal electroencephalography (EEG) to produce a digital 'bispectral index', or BIS number on a scale of 0 to 100. A BIS number of 0 equals EEG silence, and 100 is the expected value in a fully awake, conscious adult. Between 40 and 60 is recommended by the manufacturer for a level of general anesthesia. The 'SEDline' monitor (Hospira, Lake Forest, IL) also records frontal EEG and produces a comparable 0 to 100 index.
In recent years these monitors have been applied outside of anesthesiology, e.g. to dying patients at or near the moment of death, revealing startling end-of-life brain activity.
In a study reported in the Journal of Palliative Medicine, Chawla et al. (5) reported on 7 critically ill patients from whom life support (medications, machine ventilation) was being withdrawn, allowing them to die peacefully. As per protocol, they were monitored with a BIS or SEDline brain monitor. While on life support the patients were neurologically intact but heavily sedated, with BIS or SEDline numbers near 40 or higher. Following withdrawal, the BIS/SEDline generally decreased below 20 after several minutes, at about the time cardiac death occurred. This was marked by lack of measurable arterial blood pressure or functional heartbeat. Then, in all 7 patients' post-cardiac death, there was a burst of activity as indicated by abrupt rise of the BIS or SEDline to between 60 and (in most cases) 80 or higher. After a period of such activity ranging from one minute to 20 minutes, the activity dropped abruptly to near zero.
In one patient, analysis of raw SEDline data revealed the burst of post-cardiac death brain activity to be apparent gamma synchrony, an indicator of conscious awareness. Chawla et al. raise the possibility that the measured post-cardiac death brain activity might correlate with NDEs/OBEs. Of course the patients died, so we have no confirmation that such experiences occurred.
In another study published in the journal Anesthesia and Analgesia, Auyong et al. (6) describe three brain-injured patients from whom medical and ventilatory support were withdrawn prior to 'post-cardiac death' organ donation. These patients were hopelessly brain-damaged, but technically not brain dead. Their families consented to withdrawal of support and organ donation. Such patients are allowed to die 'naturally' after withdrawal of support, then quickly taken to surgery for organ donation.
The three patients in the Auyong et al. study prior to withdrawal of support had BIS numbers of 40 or lower, with one near zero. Soon after withdrawal, near the time of cardiac death, the BIS number spiked to approximately 80 in all three cases, and remained there for 30 to 90 seconds. The number then abruptly returned to near zero, followed thereafter by declaration of death and organ donation. Various sources of artifact for the end-of-life brain activity were considered and excluded.
Auyong et al. did not consider the possibility of NDEs correlating with the observed end-of-life brain activity, nor did an extensive editorial accompanying their article (7).
Obviously we can't say whether end-of-life brain activity is indeed related to NDEs/OBEs, or even possibly the soul leaving the body. Nor do we know how commonly it occurs (10 out of 10 in the two studies cited). Those issues aside, the mystery remains as to how end-of-life activity occurs in brain tissue which is metabolically dead, receiving no blood flow nor oxygen. The BIS and SEDline numbers, indicators of level of awareness, are near zero. Then, a burst of synchronized, coherent bi-frontal brain activity occurs, seemingly gamma synchrony EEG (an indicator of consciousness). As marked by BIS and SEDline numbers near 80, the activity persists for a minute or more. Then it abruptly ceases.
There are proposed explanations for the end-of-life brain activity as non-functional, generalized neuronal depolarization. Chawla et al. suggested excess extracellular potassium causes last gasp neuronal spasms throughout the brain. But that couldn't account for the global coherence - synchronized, organized. Another suggested cause is calcium-induced neuronal death which could implicate disruption of cytoskeletal microtubules inside neurons as the precipitating factor. But again, how and why the bifrontal coherent synchrony?
Perhaps the end-of-life brain activity IS related to conscious NDEs or even OBEs, but without the 'Near', i.e. the patients have the experience and are not revived. White light, tunnel, serenity, deceased loved ones, floating life review. What would that imply?
Some see NDEs/OBEs as metaphysical or spiritual events, manifestations of consciousness, or the soul, leaving the body (8). Skeptics suggest NDEs/OBEs are hallucinations or illusions, manifestations of an ischemic/hypoxic brain (9). But hypoxic/ischemic patients, if conscious, are confused, agitated and don't form memory.
If end-of-life brain activity does correlate with conscious NDE/OBE phenomenology, we still face the question of how/why conscious activity of any sort is occurring in the nearly dead brain. But here we at least have some logical possibilities based on disparities between energy requirements for consciousness and other brain functions. Neuronal hypoxia and acidosis would disable sodium-potassium ATPase pumps, preventing axonal action potentials, but temporarily sparing lower energy dendritic activity which may correlate more directly with consciousness (10), Another possibility is that consciousness is a low energy quantum process (11), in which case reduced molecular dynamics may limit thermal decoherence, providing a temporal window for enhanced quantum coherent states and a burst of enhanced consciousness. A quantum basis for consciousness also raises the scientific possibility of an afterlife, of an actual soul leaving the body and persisting as entangled fluctuations in quantum spacetime geometry (12).
We can't as yet say for sure, but end-of-life brain activity could very well represent NDEs/OBEs phenomenology which is remarkably consistent among subjects, generally pleasant and often described as life-changing and helpful. Even skeptics of NDEs as metaphysical, soul-related events contend they convey beneficial effects to survivors (9). They should be valued.
Anesthesiologists or other physicians taking care of such patients face several ethical dilemmas. Following withdrawal of support such patients may exhibit the 'appearance of suffering': labored breathing, sweating, grimacing. Whether the patient is actually suffering depends on whether they have any conscious awareness. Given that the BIS and SEDline numbers are low, they probably are not conscious. But we don't know for sure. Physicians would normally treat such signs with sedative and/or pain-killing drugs. However without ventilatory or medical support, such intervention could be seen as 'hastening demise', pushing the patient toward death. The American Society of Anesthesiologists prohibits such interventions, as do hospital protocols for post-cardiac death organ donation. We do not actively push patients toward death.
Now, end-of-life brain activity and the possibility of NDE/OBE phenomenology present another dilemma - how to avoid actions which could conceivably prevent end-of-life brain activity, as that could be seen as also preventing NDEs/OBEs, and perhaps even the soul from leaving the body.
We think the optimal management in end-of-life patients with apparent suffering is to give ketamine which alleviates suffering without hastening demise (ketamine does not generally depress breathing nor cardiovascular function). Moreover ketamine by itself has been suggested to induce NDE-like phenomenology (4), elevate BIS numbers during anesthesia(13), and could preserve or possibly enhance end-of-life brain activity, whatever it actually is.
Based on the possibility that end-of-life brain activity could correspond with NDE/OBE phenomenology, or even the soul leaving the body, end-of-life patients deserve to have it. We want it. Patients and their families should be aware of this when making agonizing decisions about withdrawal of support and organ donation.
End-of-life brain activity just may be a sign of the soul.
Stuart Hameroff, MD
Diplomate, American Board of Anesthesiology
Professor, Anesthesiology and Psychology
Director, Center for Consciousness Studies
University of Arizona, Tucson, Arizona
Deepak Chopra, MD
Co-Director of Chopra Center for Well Being
Author of over 56 books
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