According to a Dutch Study conducted into the near-death experiences of 344 clinical cardiac arrest patients, 12% reported seeing phenomena such as lights at the end of the tunnel, or recently deceased relatives. Researchers have drawn a clear link between these incidences and the lack of adequate oxygen supply to the brain; and they go on to posit that OBEs occur when this lack of oxygen is paired with a gap between the stimuli occurring in the brain and the visual, kinesthetic and auditory messages the patient receives from without.  

It’s interesting that Rosicrucian Order AMORC’s own ritual practices involve long periods of withholding your breath and a particular focus on the cardiac region of the body. Coincidentally, these practices are also combined with strong mental imagery which seems to be primarily focused on producing a prescribed response. In fact, students are told that if the prescribed response isn’t achieved then this is entirely a failing on their own part, and that more practice is required.