Over 250 years ago Swedenborg had much to say about the concept and what is involved with a Near Death Experience.
Has science ignored it, since it seems to be about the spirit, and is now looking because the high interest this is getting in today's world? One outcome seems to suggest that 'no brain activity' does not mean death, it means the 'receiver' is temporarily unavailable. It helps to see the mind as a separate level above, and influencing, the brain. To the point that sometimes two brains can get the same thought..
This is the link to Swedenborg and the Near Death Experience: