It is a pleasure to review a book about the science of spirituality that is refreshingly free of ideological axes to grind. The author of The Spiritual Doorway in the Brain: A Neurologist’s Search for the God Experience (London: Penguin Press, 2011), Kevin Nelson, is a clinical neurologist who treats patients with disorders of the brain. In his many years of practice he was impressed by the phenomenon of near death experiences (NDEs) and began to collect cases. Once he had a few dozen case histories in hand he, like many other investigators before him, noticed that these experiences evidenced some commonalities between them.
These common experiences included passing through a tunnel, a bright light, feeling of dying or being dead, out-of-body experience, a life review, and a feeling of peace or even bliss. What's more, these experiences happened very often in sequence and could be captured afterward in a narrative. Whether or not the experience was described in religious terms, patients often reported that it changed their outlook on life significantly, making them feel more intensely the preciousness of life and increasing their compassion for themselves and others.
Like any good scientist or clinician, Dr. Nelson wondered why NDEs had these particular characteristics. His tentative answer is that when blood flow is restricted to the brain for several minutes certain neurologic events inevitably occur—among them transient activation of brainstem reflexes which in turn, for some people, dis-inhibit REM (rapid eye movement) sleep physiology. The tunnel experience is correlated with (not due to) low blood flow to the retina. The bright light is correlated with activation of visual centers that normally occurs when REM is triggered. Feeling dead is correlated with the paralysis that normally accompanies REM activation. Out of body experiences are correlated with de-activation of the temporo-parietal junction that normally occurs in REM. Life review is correlated with activation of hippocampal structures, and bliss is correlated with activation of the reward system. The fact that the experiences occur in sequence and exhibit a narrative quality is due to REM dreaming or, more specifically, perhaps to lucid dreaming. In support of this set of proposed correlations, Nelson points out that you can get one or more components of NDEs as part of the REM experience when REM operates abnormally, as in narcolepsy, or awakenings with paralysis or even in normal dreaming. In addition, Nelson presents a small Internet survey study showing that people who have had NDEs also tend to exhibit signs of REM dis-inhibition in daily life.
While Nelson argues for strong associations between NDEs and components of REM, he argues that one possible brain model for spiritual experiences is those “in-between” states between sleep and waking consciousness with lucid dreaming being a prime example. Nelson does not claim that this sort of explanation for spiritual experiences can be or will be the whole story – merely that it is one clue we can use along the way to deriving a full theory of the brain bases for spiritual experiences. I entirely agree with this assessment.
Indeed I myself have urged (in my books on both sleep and on religion) that we need to pay special attention to the details of REM as a source for religious experience. The idea, of course, is not new. Traditional peoples all over the world considered dreams to be “doorways” or “portals” into the spirit realm and most religious traditions have developed methods to interpret and use dreams in spiritual practices. Anthropologists too have long argued that dreams are a source of religious experience but psychologists and neuroscientists have not followed up on these leads… until now.
Nelson, other scientists, and I have pointed beyond dreams to the physiology of REM and the transitions between sleep-wake states in order to understand consciousness. Alan Hobson in particular has provided detailed and elegant state-transition models of consciousness. However, scientists interested in religion have not yet used the wealth of data and theory generated from decades of study of REM and state transitions between REM and waking to understand the brain bases of religious consciousness. Nelson’s work, then, is a big step forward.
A few caveats are in order regarding Nelson’s suggestions, however. The correspondence between NDE phenomenology and aberrant REM phenomenology is not perfect. Nelson claims, for example, that the bliss experienced in NDEs may be related to activation of reward centers during REM, but REM is not reliably associated with activation of reward centers. Instead, REM is more consistently associated with activation of amygdala-related aversive and fear centers. Indeed, it may be that reward centers require REM deprivation, not activation. Similarly, Nelson claims that the experience of undergoing a “life review” during an NDE is related to activation of hippocampal structures during REM, but these structures also undergo de-activation in order to transfer memories to cortical sites during REM. Thus, access to long term memory stores is not reliable in REM.
As Nelson knows, REM intrusion into waking consciousness has often been invoked in models for phenomena very unlike spiritual experiences – things like delirium, depression and schizophrenia. While some die-hard mechanical materialists might like to call religious beliefs and practices delusional, I do not think Nelson would want to endorse such a sweeping claim. In short, to flesh out his theory, Nelson would do well to try to spell out how you get more compassionate people, more sane people, from REM intrusions. Perhaps it is a matter of degree – does some intrusion enrich, but too much lead to disaster?