There is a collaborative group now of physicians and scientists headed by Dr. Sam Parnia from Weill-Cornell (in my neck of the woods), across the world that have dedicated themselves to scinetifically and objectively investigating NDEs.  Their theory is one discussed by many - namely that if scientists deduce that consicuosness is produced only by the human brain, then when someone is officially "brain dead," there should be no evidence of true thought or consciousness if they were subsequently revived.  If consciousness can be proven to exist in a brain dead individual during objective clinical cessation of brainwave and cardiac function, then scientists would have to reconsider whether consciousness exists independent of the physical body.  

Skeptics such as Susan Blackmore write off NDEs as mere hallucinations caused by a dying brain.  They have written several cogent papers on why NDEs do not stand up to scrutiny (although interestingly enough Blackmore has recently recanted her skeptical stance and does not wish to give interviews or discuss the matter further).  

This collaborative scientific investigation will place scientific recording equipment in emergency rooms and ICUs, and will also place words, writing and messages in places where a "floating consciousness" would be able to read them in an OOBE.  They will systematically study the proof of lack of cardiac and brain activity in those who die and then "come back."  

This is one of the greatest scientific studies ever formulated.  Hopefully, something positive will come of it.

The link is:

http://www.cbsnews.com/stories/2001/06/28/tech/main298885.shtml

Matthew