There's an intriguing if flawed article on the subject in Salon here.
Materialistic scientists have proposed a number of physiological explanations to account for the various features of NDEs. British psychologist Susan Blackmore has propounded the “dying brain” hypothesis: that a lack of oxygen (or anoxia) during the dying process might induce abnormal firing of neurons in brain areas responsible for vision, and that such an abnormal firing would lead to the illusion of seeing a bright light at the end of a dark tunnel.Would it? [ NDE researcher Pim] van Lommel and colleagues objected that if anoxia plays a central role in the production of NDEs, most cardiac arrest patients would report an NDE. Studies show that this is clearly not the case. Another problem with this view is that reports of a tunnel are absent from several accounts of NDErs. As pointed out by renowned NDE researcher Sam Parnia, some individuals have reported an NDE when they had not been terminally ill and so would have had normal levels of oxygen in their brains.
I'm not quite sure what to make of this, though I would expect that there would be some physical (chemical/electrical/mechanical) trace of the NDE - that is, if someone remembers an NDE it should do so by an observable change in their brains post facto. I expect that the cessation of metabolic (and hence chemical/electrical/mechanical) processes should, as a physical process itself, be a closed system.
And it well might be, and be the case that consciousness is not entirely contained in neural areas.
It goes without saying the parallels to Buddhist concepts are potentially profound - Buddha nature evidently does pervade the universe, and not as some kind of faint hope either.
More to the point, - or changing direction of this post somewhat - the change of awareness and acceptance of all that we are, all the muck and goo and anger and weakness and vulnerability - that can be employed as a force for the good, far more powerfully than reading about the NDE of someone else. I had to go an extra few feet for someone yesterday. The person had some problems in life I have been fortunate enough to avoid, or perhaps I'd experienced them in different ways. I didn't at first know why it was important for me to do what I did, but I think it was because it was a great way to acknowledge and say "no" to all the crap we'd all experienced in life. I was listening to a talk from Genjo Marinello the other day on resoluteness in practice. I think you need a smidgen of something with excitement that feels a little like anger to cultivate that resolution.