I've never had an NDE, but I've had an OBE -- out of body experience.
Many NDE's can be explained by scientists as spontaneous firing of neurons under trauma and/or drugs (as in surgery, illness or accident). That doesn't mean scientists are right all or even some of the time on this.
My own experience was entirely spiritual. I was participating in spiritual counseling at the Church of Scientology in Los Angeles, California. It was about 1971 and the counseling was called "Power Processing." And powerful it was!
All I remember of the counseling questions was that it involved other people and relationships. Suddenly, the room went gray and seemed like a tunnel where all I could clearly see was the counselor -- a fine chap named David Light (AOLA's Director of the Treasury or "purser").
The next moment, I couldn't feel the chair I was in, couldn't hear him, or see anything in the room. In fact, I was no longer in my body. I saw the ground 15 feet below and the side of the building in which my body still sat. I could see the cracking and heavily textured pink stucco, plus the bluish gray blinds (closed) in the window between me and my body. I could also see the near-empty parking lot of the Chez Claude restaurant, next door, with its large ball light fixtures.
The moment I realized that the light was passing through me and that I was not casting a shadow, I found myself back in my body.
It took me over 40 years to figure out why. When I became self-conscious, I was descending back into ego (the false self we use to exist in this physical realm). With ego, we cannot see any more -- thus the Bible's description as "Darkness."
I realized only last month that only by subduing ego entirely can we awaken the true self (the immortal spirit, soul, Holy Ghost), within, and return to our lack of dependence on physical eyes and see with our own true sight -- called the "Light."