Kevin Nelson and his colleagues at the University of Kentucky have presented evidence suggesting that, with the compromise of cerebral blood flow, there is a dissociation of consciousness so that, although awake, the subjects are paralyzed and subject to the dreamlike hallucinations characteristic of REM sleep (“REM intrusions”)—in a state, therefore, with resemblances to sleep paralysis (NDEs are also commoner in people prone to sleep paralysis). Added to this are various special features: the “dark tunnel” is correlated, Nelson feels, with the compromise of blood flow to the retinas (this is well known to produce a constriction of the visual fields, or tunnel vision, and may occur in pilots subjected to high g-stresses). The “bright light” Nelson correlates with a flow of neuronal excitement moving from a part of the brain stem (the pons) to subcortical visual relay stations and then to the occipital cortex. Added to all these neurophysiological changes may be a sense of terror and awe going with the knowledge that one is undergoing a mortal crisis—some subjects have actually heard themselves pronounced dead—and the wish that dying, if imminent and inevitable, should be peaceful and perhaps a passage to a life after death.
Both Olaf Blanke and Peter Brugger have studied such phenomena in several patients with severe epilepsy. Like Wilder Penfield’s patients in the 1950s, people with intractable seizures that do not respond to medication may need surgery to remove the epileptic focus responsible. Such surgery requires extensive testing and mapping to find the seizure focus and to avoid damaging vital areas. The patient must be awake during this procedure, so that he can report what he is experiencing. Blanke was able to demonstrate that stimulating certain areas of the brain’s right angular gyrus invariably caused OBEs in one such patient, as well as feelings of lightness and levitation and changes in body image; the patient saw her legs “becoming shorter” and moving towards her face. Blanke et al. speculate that the angular gyrus is a crucial node in a circuit that mediates body image and vestibular sensations, and that “the experience of dissociation of self from the body is a result of failure to integrate information from the body with vestibular information.”
At other times, one is not disembodied but sees a double of oneself from one’s normal viewpoint, and the other self often mimics (or shares) one’s own postures and movements. These autoscopic hallucinations are purely visual and usually fairly brief—they may occur, for instance, in the few minutes of a migraine or epileptic aura. In his delightful history of migraine, “Migraine: From Cappadocia to Queen Square,” Macdonald Critchley describes this in the great naturalist Carl Linnaeus:
Often Linnaeus saw “his other self” strolling in the garden parallel with himself, and the phantom would mimic his movements, i.e. stoop to examine a plant or to pick a flower. Sometimes the alter ego would occupy his own seat at his library desk. Once at a demonstration to his students he wanted to fetch a specimen from his room. He opened the door rapidly, intending to enter, but pulled up at once saying, “Oh! I’m there already.”
A similar hallucination of a double was seen regularly by Charles Lullin, the grandfather of Charles Bonnet, for about three months, as Douwe Draaisma describes:
One morning as he was quietly smoking his pipe at the window, he saw on his left a man leaning casually against the window frame. Except for the fact that he was a head taller, the man looked exactly like him: he was also smoking a pipe, and he was wearing the same cap and the same dressing gown. The man was there again the next morning, and he gradually became a familiar apparition.
The autoscopic double is literally a mirror image of oneself, with right transposed to left and vice versa, mirroring one’s positions and actions. The double is a purely visual phenomenon, with no identity or intentionality of its own. It has no desires and takes no initiatives; it is passive and neutral.74
Jean Lhermitte, reviewing the subject of autoscopy in 1951, wrote: “The phenomenon of the double can be produced by many other diseases of the brain besides epilepsy. It appears in general paralysis [neurosyphilis], in encephalitis, in encephalosis of schizophrenia, in focal lesions of the brain, in post-traumatic disorders. . . . The apparition of the double should make one seriously suspect the incidence of a disease.”
