Michael Persinger, a neuroscientist at Laurentian University in Sudbury, Ontario, built his reputation on the claim that mystical and religious experience could be an artifact of ordinary temporal lobe function rather than evidence of contact with anything outside the brain. His 1983 paper laid out the general hypothesis that weak, complex magnetic fields applied to the temporal lobes could destabilize their normal activity enough to produce sensations resembling a felt presence, out-of-body feeling, or religious experience, depending on the individual's prior beliefs and expectations.
To test it, Persinger's lab built a modified motorcycle helmet, sometimes called the Koren helmet after its designer Stanley Koren, fitted with solenoids that delivered a weak, patterned magnetic field to the wearer's temporal lobes while they sat in a dark, quiet chamber. Hundreds of participants over more than a decade reported experiences ranging from a vague sensed presence to vivid religious or mystical episodes, which Persinger read as support for a neurological, rather than external, account of such experiences.