Hallucinations

Shadows” and “doubles” — hallucinatory distortions of the body and body image — take us into an even stranger realm. If a limb or part of the body is “deanimated” by nerve or spinal cord damage, the deanimated part itself may feel lifeless, inorganic, alien. But if there is damage to the right parietal lobe, a much deeper form of estrangement may occur. The deanimated part of the body — if its existence is acknowledged at all — is felt to belong to someone else, a mysterious “other.” Many years ago, as a medical student, I saw a patient who had been admitted to the neurosurgery service for removal of a parietal lobe tumor. One evening, while awaiting surgery, he fell out of bed in a peculiar way — almost, the nurses said, as if he had thrown himself off the bed. When I asked him about this, he said that he had been asleep and awoke to discover a leg — a dead, cold, hairy leg — in his bed. He could not think how someone else’s leg had got into his bed, unless — the idea suddenly occurred to him — the nurses had taken a leg from the anatomy labs and slipped it into his bed as a joke. Shocked and repelled, he used his good right leg to kick the alien thing out of his bed, and, of course, he came out after it, and was now aghast because “it” was attached to him. I said, “But it is your leg,” and pointed out to him that the size, the shape, the contour, the color were precisely the same in the two legs; but he would have none of it. He was absolutely certain that it was someone else’s.

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Over the years I have seen other patients who, in consequence of a right-hemisphere stroke, have lost all feeling and use of the left side. Often they have no awareness that anything has happened, but some people are convinced that their left side belongs to someone else (“my twin brother,” “the man next to me,” even “It’s yours

, Doc, who are you kidding?”). Perhaps “my twin brother” is a hieroglyphic way of indicating that while half of the body seems alien, it also seems very akin, almost identical to oneself … that it is oneself in a strange, disguised way. It needs to be emphasized that such patients may be highly intelligent, lucid, and articulate — and that it is solely in reference to their odd distortions of body image that they make their surreal but irrefragable statements.

The feeling that someone is there

, to the left or the right, perhaps just behind us, is known to us all. It is not just a vague feeling; it is a distinct sensation. We may wheel around to catch the lurking figure, but there is no one to be seen. And yet it is impossible to dismiss the sensation, even if we have learned from repeated experience that this sort of sensed presence is a hallucination or an illusion.

The sensation is commoner if one is alone, in darkness, perhaps in unfamiliar surroundings, hyperalert. It is well known to mountaineers and polar explorers, where the vastness and danger of the terrain, the isolation and exhaustion (and, in the mountains, reduced oxygen) contribute to the feeling. The sensed presence, the invisible companion, the “third man,” the shadow person — all sorts of terms are used — is well aware of us, and has definite intentions, whether these are benign or malignant. The shadow stalking us has something in mind. And it is this sense of its intentionality or agency which either raises the hair on our neck or produces a sweet, calm feeling of being protected, not alone.

While the sense of “somebody there” is commoner in the hypervigilant states induced by some forms of anxiety, by various drugs and by schizophrenia, it may also occur in neurological conditions. Thus Professor R. and Ed W., who both have advancing Parkinson’s disease, have persistent feelings of a presence — something or someone they never actually see; this presence is always on the same side. There may be a transitory sense of “someone there” in attacks of migraine or in seizures — but a very persistent sense of a presence, always to the same side, is suggestive of a brain lesion. (This is also the case with such experiences as déjà vu, which we all have occasionally, but which, if very frequent, suggests a seizure disorder or a brain lesion.)