Is X the Explanation of the Near Death Experience (NDE)?

“If you ignore everything paranormal about NDEs, then it’s easy to conclude, there’s nothing paranormal about them.”

- Bruce Greyson

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If you want to stand on the shoulders of giants, it involves a lot of legwork - good research and journalism involve a long paper trail, synthesizing evidence and perspectives to try and best make sense of complex phenomena. There are some times when a completely naive perspective can provide valuable insight, but for the most part, you ignore the work of others to your own detriment.

It seems like every year or two, there's an article proclaiming a "new explanation" of the NDE, but these articles often contain little that is new or explanatory to those who are familiar with the literature. These "explanations" are usually only relevant to certain occurrences of the NDE, such as cases occurring in cardiac arrest, without any acknowledgement of this limitation in scope. A telling omission in such papers is the absence of any reference to the Handbook of Near Death Experiences or any attempt to refute the arguments put fourth by its authors. Instead of looking at a comprehensive review of the literature, some authors continue to propound ideas that have already been shown to be woefully inadequate, which I imagine is terribly frustrating to those actually seeking to understand the NDE.

Here's a couple suggestions to keep the NDE literature moving forward:

1. Do a comprehensive literature review. While this should go without saying, I've seen too many articles put fourth ideas that have been called into question in previous research, without ever acknowledging or addressing these issues. It's impossible to have a dialog without understanding the state of the literature.
2. Acknowledge the scope of your research. The NDE is a complex phenomenon which occurs in response to many different events. Limiting the scope of research is fine, but at least acknowledge that your findings may not generalize beyond a specific context (e.g. cardiac arrest).
3. Tackle the thorny issues. While prospective studies of apparent veridical perception are still underway, in my opinion, there's enough evidence out there to warrant serious scientific consideration.

Changing Trains - A Reflection

I am a big fan of Randi's Prize, so when Robert Mcluhan had a post on his blog about changing worldviews, I thought I'd do a bit of reflection on where I've been.

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Although I grew up in a Catholic household, was confirmed, and even was an altar server for several years, I never saw eye-to-eye with the church. Even in elementary school, I was incredulous that some people ascribed to biblical literalism, and didn't seem to give much thought to the problem of evil, or the innumerable archaic laws and acts of barbarism of the Old Testament- needless to say, these thoughts made for some uncomfortable moments in CCD. I learned to keep these to myself, along with my fondness for the Bhagavad Gita.

My views on religion took drastic turns in college, where I encountered the extremes of religion for the first time. As someone who believed that our intelligence and curiosity were integral parts of the human experience, I was profoundly disturbed by my first encounters with religious fundamentalists, who unswervingly believed that the Bible supplanted any textbook on the physical or biological sciences, and viewed a class on evolution as a test of their faith. I had honestly never met anyone before who trusted dogma more than their own faculties or believed that prayer is the only acceptable treatment for disease.

After witnessing the frightening effects of fundamentalism on the mind, I began to increasingly identify with the ideals skeptical movement, naively hoping that a dose of rational inquiry would cure some of what ails the world. A university education in biology and psychology had convinced me that biological naturalism was the only logical answer to the mind-body problem, and I came to believe that anything outside mainstream science was a slippery slope to irrationality and superstition. Full of hubris, I derided anything associated with the paranormal, since I was already sure that the world fit neatly into my materialist worldview, and I had seen the battery of many paranormal straw men at the hands of the skeptical movement. Looking back, it was terribly ironic how my commitment to "skeptical inquiry" made me view actual skeptical inquiry into paranormal topics as a waste of time, since I'd already become convinced that such research was pointless.

In an even more ironic twist of fate, it was this hubris that actually lead me to challenge my prior beliefs. I was in the library one day, and happened to see a flier advertising a talk about some paranormal phenomenon. Eager to self-righteously assert my rationalism, I went off to find a legitimate (read: skeptical) book on the topic. While rifling through the shelves, looking for another book, I ended up picking up a copy of The Handbook of Near-Death Experiences on a whim. Unbeknownst to me, this book was not about to lead me to the conclusion I expected.

After my assumptions about the near-death experience (NDE) were roundly refuted, the next few months were spent grappling with cognitive dissonance and what McLuhan calls "rational gravity." Was I missing something obvious? Was I losing my ability to reason? If not, are there other ostensible paranormal phenomena which merit reconsideration? On one hand, it was exciting to learn about the mind-boggling phenomenon of the NDE, but this excitement came with the emotional baggage of having to grapple with what appeared to be a serious challenge to my worldview. This was the first time I encountered the type of serious rational inquiry to which I was supposedly committed, and it bore no resemblance to the straw men which I had previously encountered. This experience began to chip away at my confidence in "skeptical inquiry," and made me realize that I might have to entertain ideas that I'd previously dismissed as absurd, such as dualism or psi. I began to worry that if I began to dig deeper, I would soon be sliding down the slippery slopes into the land of woo woo.

So with great trepidation, down those slopes I went, reading about deathbed visions, cases of the reincarnation type, apparitions, mediumship, and so on - topics that I would have laughed off a few months beforehand. While there are a great number of ostensible paranormal cases which are not objectively evidential or could potentially be attributed to fraud, cognitive biases, cryptomnesia, false memories, inadequate controls, and so fourth, the best cases I've encountered seemed to elude a materialist explanation. I find the topics of psi and survival particularly intriguing, but I'm still unsure what to make of them. Right now, all I can be sure of is that actual skeptical inquiry is far more interesting than derision and confirmation bias.*

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* This is poking fun at myself and my own cognitive biases, not anyone else - It doesn't matter to me whether you're a fence-sitter, or are on one side or another, so long as you're actually inquiring.

Reports of my Near-Death Have Been Greatly Exaggerated

Stop me if you've heard this one, but there's finally a reductionist materialist explanation of the near death experience (NDE)- seriously, they mean it this time. All of these articles are loosely based on a recent publication in PNAS, which found intense, synchronous EEG activity in a sample of 9 anesthetized mice in the 30 seconds immediately following experimental cardiac arrest¹. So does this unequivocally show that NDEs are the hallucination of a dying brain, or is this a kernel of interesting neurophysiology caught in a snowball of hyperbole and polemic?

For those interested in using data for illumination, not support, let's take a step back and try and put this study into context. The NDE is a complex phenomenological experience often associated with a life-threatening event. While NDEs can occur during cardiac arrest, they have also been reported in response to trauma, illness, and drownings, even when an individual may not be in mortal danger. An adequate explanation of the NDE has proven elusive, since it must account for apparent consciousness, perception, and memory during a period in which the brain seems incapable of supporting these functions.

Proposed Physiological Explanations for NDE Phenomena

Biological hypotheses proposed to account for the NDE range are usually based on a hodgepodge of superficially similar phenomenology associated with hypoxia, hypercarbia, REM intrusion, epilepsy, psychoactive drugs, dissociation, endorphins, and gravity-induced loss of consciousness, but these analogies fall apart under any scrutiny^2,3. Susan Blackmore argued the dying brain hypothesis, attempting to explain NDE phenomenology as hallucinatory experiences created by a brain starved of sensory input and blood flow⁴. While Blackmore's ideas initially sound convincing, and they were initially an important contribution to the discussion of the NDE, the advancement of the field has really put them out to pasture^2,3. Since there's not really a good materialist alternative to the dying brain hypothesis, it often gets touted as scientific consensus, irrespective of its glaring omissions, and any research which appears to support it at first glance is heralded as the explanation of the NDE.

The Borjigin et al. Study & The Dying Brain Hypothesis

If we observe coherent brain activity in rats after cardiac arrest, is this even relevant to the phenomenal experience of the NDE? First, we should note that we have no way of inferring about the phenomenal experience of rats during this burst of brain activity. Secondly, this burst of activity hasn't been seen in humans, although electrodes on the scalp are probably not as sensitive as electrodes implanted in the brain. Thirdly, even if this activity did occur in human beings, we have no idea if it is actually related to conscious experience - I'm not an expert in EEG, but I do know that synchronous activity can occur in seizures, whose phenomenology is different from the NDE.

In my opinion, this finding isn't terribly relevant to the human phenomenal experience during cardiac arrest, but it is intriguing. The brain has extremely high metabolic demands to sustain the constant depolarization and repolarization of neurons. We shouldn't expect an immediate, complete abolition of brain activity after cardiac arrest, but the synchronicity of the activity is very intriguing. It's also interesting to note that even when implanted EEG electrodes were used, giving us one of the best windows into brain activity, all coherent activity was abolished within 30 seconds of cardiac arrest, which is consistent with research in humans. It appears that any sustained consciousness, perception, and memory after this period would not be explained by a neural basis.

If this activity does occur in some or all humans after cardiac arrest, does this explain the NDE? Not really, since the NDE can occur in the absence of injury, and can be shared between individuals, all of which argues against the dying brain hypothesis^2,3,5. It also makes one wonder how a very brief flurry of neural activity could be responsible for both generating a vivid conscious experience while simultaneously encoding it in memory for later recovery, especially when trauma to the brain is typically associated with both absence of consciousness and loss of memory².

Principle of Charity - Does This Explain The NDE?

Let's grant those seeking to bolster the dying brain hypothesis with the results of the Borjigin et al. study a couple premises, which in my opinion, are not well supported to date:

1. The coherent activity observed in rats was associated with conscious experience
2. Similar activity occurs in humans, but has not been observed due to measurement limitations
3. The experiences associated with the NDE occur in this burst of activity

Aside: If someone can explain how we're to soundly infer about the phenomenal experience of rats from their EEG, I'm sure Thomas Nagel would have your full attention.

The NDE is not just the "experience," as one of the thorniest issues is how individuals with severely compromised brain function are able to not only have conscious experiences, but have accurate memory and perception. Furthermore, this apparent veridical perception (AVP) can occur in individuals whose eyes were covered in gauze in preparation for surgery, the comatose, and even those blind from birth^2,3. If NDEs were just hallucinatory experiences of a dying brain, it seems unlikely that they'd occur in the absence of injury, be consistent with reality, and potentially even shared between multiple people⁵.

Common "explanations" for apparent veridical perception are based on the assumption that while brain activity on the cortical surface may be abolished, there might be deep brain activity which could somehow explain the phenomena. Research in humans and this latest study in rats demonstrate that even when electrodes are implanted in the brain, it appears that EEG activity is abolished within 30 seconds of cardiac arrest, arguing against deep brain activity as an ostensible explanation of AVP.

So What Have We Learned Today?

In summary, the Borjigin et al. study is quite intriguing, and a valuable addition to the neurophysiology and NDE literature. Like most studies into a complex, interesting phenomenon, it raises far more questions than it does answers. Unfortunately, it appears that a level-headed discussion of this finding in the context of the larger picture hasn't happened yet, and that's quite disappointing. Even when we grant several unsupported premises to the dying brain hypothesis, it still doesn't adequately explain the NDE^2,3. This latest finding is not germane to NDEs occurring in the absence of injury, and may even argue against the dying brain hypothesis in some well documented accounts, such as those of Al Sullivan and Pam Reynolds.

Take note, pop-sci "journalists," this is how it's done. Since you're paid by the click, I know you're not about to let a body of research get in the way of a good sensationalist headline.

1. Borjigin J, Lee U, Liu T, Pal D, Huff S, Klarr D, Sloboda J, Hernandez J, Wang MM, Mashour GA. Surge of neurophysiological coherence and connectivity in the dying brain. PNAS USA. 2013 Aug 12.

2. Holden JM, Greyson, B, and James D, eds. The Handbook of Near-Death Experiences: Thirty Years of Investigation. Santa Barbara, CA: Praeger, 2009.*

3. Carter C. Science and the Near-Death Experience: How Consciousness Survives Death. Toronto: Inner Traditions, 2010.

4. Blackmore S. Dying to Live: Near-Death Experiences. London: Grafton, 1993.

5. Moody RA and Perry P. Glimpses of Eternity: Sharing a loved one's passage from this life to the next, New York, NY: Guideposts, 2010.

* I can't recommend this book highly enough: if you're genuinely interested in learning about the NDE, this book is truly unparalleled - Before anyone publishes another "explanation" of the NDE, you should learn from those who have been researching the topic for decades.