'Dying Brain Hypothesis' Not Dead
Interested to see The Skeptic magazine taking a pop at Pim van Lommel's hospital study of near-death experiences in its recent issue. This study, originally published in the medical journal The Lancet in 2001 has been hugely influential, so its not surprising the mag wants to cut it down to size.
Van Lommel and his team spent 13 years interviewing patients in ten different Dutch hospitals who had been resuscitated following a cardiac arrest. The aim was to see whether they had experienced an NDE. Eighteen per cent reported some memory from their period of unconsciousness, and 12% - one in eight - experienced several of the classic features: out-of-body perception, the tunnel, the light, blissful feelings, panoramic life review, and so on. Van Lommel concluded that medical factors could not account for the phenomenon. If purely physiological factors resulting from cerebral anoxia were the cause, he reasoned, most of the patients should have had an NDE.
This piece is by Jason J. Braithwaite, a researcher in visual cognitive neuroscience. He argues that survivalists like van Lommel have 'repeatedly misunderstood and misrepresented the dying-brain hypothesis when trying to argue against it'. According to this theory, as formulated by Susan Blackmore and others, it's not the mere presence of anoxia that causes vivid seeming hallucinations, but the rate of its onset. If it comes on too rapidly, the patient will lose consciousness and black out, so no conscious experience or memory could occur.
However van Lommel made no attempt to measure the level of anoxia, so is in no position to make claims regarding its effects or the lack of them. He also, Braithwaite claims, ignores the way that anoxia impacts on different parts of the brain, and how some areas will be more susceptible than others. In any case, he goes on, it's not anoxia itself that is said to cause the NDE, but neural disinhibition, which can also be caused by drugs, epilepsy and so on.
Braithwaite also takes issue with the idea that a flat cortical EEG is an indication of total brain inactivity. Recent research with epileptics shows that large scale seizure activity can occur in deep sub-cortical regions that does not register at all on scalp-based EEG traces - an indication that an EEG is an unreliable measure of neural activity. In other words, there still lacks any reliable evidence that a person who reports an NDE was literally brain-dead at the time. He cites evidence that inter-ictal discharges in the hippocampus or amygdala alone are more than sufficient to produce complex meaningful hallucinations - no involvement from the cortex is necessary.
In short, he concludes that the dying brain hypothesis lives on - van Lommel's data notwithstanding. That should be pretty cheering to the Skeptic's readers. The article is forcefully argued and will leave them with the impression that all the fuss about van Lommel's study has been overdone, that it provides zero support it provides for the claims of survival, and so there's nothing to worry about.
Will it impact on the wider debate? Braithwaite knows his stuff, and his points about anoxia and EEG read-outs are probably quite relevant. It confirmed my feeling that the whole business of trying to prove that an individual could not possibly have had the experience since nothing was going on in his/her brain at the time - and certainly nothing that could have accounted for it - is fraught with difficulty. To that extent he's done a good job, and he's certainly a forceful advocate for the sceptic position.
But those of us who get our information from other sources besides sceptic magazines will not be left much further on. It's all very well to beat off attacks on the so-called dying brain hypothesis, but I've never been very certain what this ever actually amounted to. It's a rather grand term that implies to the uninitiated that the entire pantheon of effects in the near-death experience - any one of which is pretty surprising on its own, but which in combination many people justly find to be hugely meaningful and impactful - can somehow be explained away on the basis of neurological activity, whose effects we can only describe in very general terms. What the patient saw wasn't there, so it must have been a hallucination, and anoxia is implicated in neural disinhibition which causes hallucinations. There's your explanation. What more do you want?
I often wonder whether sceptics understand the enormity of what they are trying to explain away. (I remember coming across Michael Shermer somewhere referring to the near-death experience as 'obviously a wishful hallucination' - what magisterial certainty!) At one point Braithwaite raises the subject of the 'vivid and meaningful experiences' that are reported by patients undergoing brain stimulation, and which van Lommel argues are quite unlike the near-death experience. Van Lommel says:
These recollections ... consist of fragmented and random memories unlike the panoramic life-review that can occur in NDE. Further, transformational processes with changing life-insight and disappearance of fear of death are rarely reported after induced experiences. ... Thus, induced experiences are not identical to NDE...
That seems the very least one can say, but Braithwaite thinks 'this claim is not entirely accurate'. He suggests that the context of the two events - one when the patient is relaxed and enjoying a constant controlled interaction with the surgeon and receiving constant feedback, the other where the patient is possibly undergoing some form of trauma, confusion, disorientation, etc - may play a part.
It is certainly not unreasonable to assume that the small experiential differences between NDE and brain stimulation studies can be explained, to some degree, by these large differences in context. This is certainly a far more probably conclusion than that of mind-brain dualism.
It's a nice try, but... small experiential differences? Braithwaite quotes several sources, among which I recognised Wilder Penfield, the neurosurgeon whose book on this subject I read some years ago, and whose work poking around in the brains of conscious epileptics I'm certain produced nothing remotely comparable to the panoramic life review or the ineffable feelings commonly described in the NDE, to name only two. But that's the nub of all this - for some people, absolutely anything is more probable than mind-brain dualism. Like all paranormal debunkers, the author radiates indignation at the idea, and the irresponsibility of those who dare to suggest it.
The fact is, for those who can recognise the challenge here, the dying brain hypothesis is not really a hypothesis at all - it's a set of defensive stratagems based on inaccurate comparisons and speculative generalisations. Some of it sort of hangs together if you don't look too closely at what experiencers actually say - Blackmore's idea of the dying cells in the visual cortex causing the tunnel effects has certainly gained traction in this regard. But in other respects it just relies on bluff and misinformation - Blackmore's chapter on out-of-body perception in Dying to Live being a prime example.
What I find so interesting is that in the sceptical analysis the transcendental and transormative element hardly gets any mention at all. OK, there may be something going on at some deep level of the brain, beyond the ability of instruments to detect. But is that really the point? Patients aren't just continuing to have experiences, something happens to them so powerful that when they return to existence they think and behave differently. What possible, meaningful neurological explanation could there be for that?
My feeling is that no materialist account of the NDE will be complete until we address this. We should surely all by now be able to recognise that it's a coherent and relatively common human experience, and one that has relevance to the human condition, on a personal and on a cultural level. So let's stop pretending that it's simply some weird nonsense that happens when the brain winds down, and nothing really to worry about. Let's instead ask ourselves why, if we are the creatures formed by natural selection that believe ourselves to be, something as odd and yet as meaningful as the near-death experience could ever have evolved. What's the purpose of it?
http://monkeywah.typepad.com/paranormal ... -dead.html
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