Have you read any pop neuroscience book? There are common experiences that can be generated by one or another kind of brain-wrong. You sort of acknowledged this already when you mentioned DMT. If you poke somebody in specific parts of the brain you can get illusions of changing size, shadowy figures, mirth, and other delightful errors. We also interpret things very eagerly, like the "night hag" phenomenon where being unable to sense one's own breathing turns into an illusion of something sitting on your chest. That's another worldwide cross-cultural concept, by the way, but there is no night hag, there's just human physiology.

So, bright lights and tunnels. Shared human visual neurological glitches. Heard of "tunnel vision"? That's a real medical condition, which can be caused by blood loss, adrenaline, or low oxygen.