It is released from high-tension powerlines, microwave ovens, lightning, and anything which runs on electricity. The brain is also a electro-chemical organ bombarded by electrical impulses. If these electric currents are disrupted in any way, it can cause hallucinations, false memories, and false experiences. To test this theory, Dr. Persinger sets up an experiment where he blindfolds a person, places a weak electromagnetic field helmet on their head, and puts them in a sound-proof room. Then he leaves the chamber and changes the shape of electromagnetic waves entering the test patient's brain from his control panel.
Different wave shapes cause different hallucinations.
This explanation makes a lot of sense when dealing with alleged alien abductions. Commonly reported are electrical interference which usually precedes a UFO sighting or alien abduction. Also note that alien abductions are a fairly recent phenomenon and coincide with the increase of powerlines and use of electrical equipment over the last 50 years. Electromagnetism is also known to levitate and throw inanimate objects including those that are not magnetic. However, studies show that this only occurs when a person is near the object, giving weight to the poltergeist phenomena.