True of a lot of things people believe in, we often can't figure out the specific reason as to why they hold on to their beliefs. We are not infrequently left in the dark. I have often wondered why researchers in neuroscience are so attached to the assumption that consciousness is, somehow, produced by the brain. Not a few researchers hold this assumption. Despite many years of work by many researchers there is still no scientific theory of how the brain creates conscious experience. What seems apparent is that these same researchers expect to find a solution which answers the question, "How does the biological brain make us experience consciousness?" This expectation, it seems clear to me, admits a strong bias: I believe that the brain makes consciousness as against, consciousness can interact with a brain but is, intrinsically, brain independent.
I imagine the reasoning of the researchers goes something like this. As a conscious being, I see physical correlates in the brain by means of an fMRI, which appear to have a mutual relationship with my conscious experiences. Therefore, I conclude that consciousness is brain generated.
But the only thing our researchers can truly say, if they were honest, is that the activity of consciousness is reflected in the mirror of the brain which the fMRI shows. In this respect, the researchers are somewhat like Narcissus in Ovid's Metamorphosis who has fallen in love with a reflected image of himself in a pool of shining water. In the same way, the researcher believes that the biological brain is vital (the image of Narcissus in the pool) and consciousness is dead or at best an illusion (the real, vital Narcissus).
In reference to the Metamorphosis, our researcher has found a substance in what is only shadow. He looks in wonder upon the fMRI. He is charmed by it, spell-bound by it. But this image, including the anatomical brain which is set in his skull, is no more self-animating than a marble statue. Ovid says, "The vision is only shadow, only reflection, lacking any substance. . . .He watches, all unsatisfied, that image vain and illusive, and he almost drowns in his own watching eyes."
Also, it should not surprise us that during an NDE the brain stem activity is flatlined. Of course there are various explanatory models warring with each other trying to explain this puzzling phenomenon from brain-centric explanations to transcendental explanations. Science comes to its limits with any and all models which are useful fictions; which give a certain explanatory power. So, it boils down to politics, that is, various persuasion strategies designed to influence the masses. But there is no Buddhism here. The Buddhist notion of mind (citta) and consciousness (vijñāna) are alien to the world of neuroscience. Here is what I mean.
"What we commonly call the mind is a set of operations carried out by the brain. Brain processes underlie not only simple motor behaviors such as walking and eating but also all the complex cognitive acts and behavior that we regard as quintessentially human—thinking, speaking, and creating works of art. As a corollary, all the behavioral disorders that characterize psychiatric illness—disorders of affect (feeling) and cognition (thought)—result from disturbances of brain function" (E.R. Kandel, J.H. Schwartz, T.M. Jessell, S.A. Siegelbaum, & A.J. Hudspeth (Eds.), Principles of Neural Science, 5th ed., p. 5).
For traditional Buddhism, such a definition of mind falls under the rubric of materialism. Buddhism, as I have said before, is a first-person science (science according to the OED is the state or act of knowing) which is the investigation of ātman, per se, or the same, my self intrinsically. The world from this position outward is immaterial or, ultimately, Mind-only. Let's call it spiritual, or a least psychological. On the other hand, the world viewed from the outside (material things) to beings is material. There is no mind of consciousness to be seen. This is the image of Narcissus who is be-spelled by the shadows—the nothingness of the reflected image.