If the brain can hallucinate, which it can, then it can certainly provide a "near death experience." Unless there is direct evidence to the contrary it has to be surmised that these experiences are the results of brain activity. End of story. But that doesn't mean the tests can't reveal interesting things about how the brain works.
As to out of body experiences, they've been testing those for years and decades and never confirmed one. An out of body experience is easier to test than a near death experience, of course, but it's really only a lucid dream or a hallucination. And of course people will see all kinds of crazy stuff.
Assuming the test subject would not cheat, Carl Sagan had proposed years and years ago a standing test: place an object or even the title of a book or a coin in a high back corner shelf, for instance, or a high place, and then at some point when the person has an out of body experience, go check to see what the object is. It would require an honest subject, though. 
Some folks have some real wild out of body stories, so it shouldn't be too hard to go check what's on the shelf.
Drugs would help people have out of body experiences and hallucinations.
