Studies show that a lot of so-called near death experiences is just a chain reaction of neurotransmitters combined with epinepherine and lack of oxygen that intterupts normal brain patterns, and your subconcious may provide images from memory.

Skeptic magazine showed that a lot of paranormal experiences can be almost exactly replicated (i.e. feeling of a presence, hearing noises, hallucinations, ect) can be caused by fluctuations in brain chemistry caused by magnetic fields.