Ian Sample reports in The Guardian:
At the University of California in San Diego, neuroscientist VS Ramachandran noticed that a disproportionate number of patients – around a quarter – with a condition called temporal lobe epilepsy reported having deeply moving religious experiences. “They’d tell me they felt a presence or suddenly felt they got the meaning of the whole cosmos. And these could be life-changing experiences,” says Ramachandran. The feelings always came during seizures, even if the seizures were so mild, they could only be detected by sensitive electroencephalograms (EEGs). Between the seizures, some patients became preoccupied with thoughts about God.
Ramachandran drew up three explanations he thought might explain why the patients with epilepsy seemed so spiritual. First, he considered that the upwelling of emotion caused by the seizure might simply overwhelm, and patients made sense of it by believing that something extremely spiritual was going on. Second, the seizure might prompt the left hemisphere to make up yarns to account for seemingly inexplicable emotions. The ability of the brain’s left hemisphere to “confabulate” like this is well known to neuroscientists. Third, he wondered whether seizures disrupted the function of part of the brain called the amygdala which, among other tasks, helps us focus on what is significant while allowing us to ignore the trivial.
Ramachandran decided to test a couple of patients using what is called the galvanic skin response.
More here.