Hallucinations

9. I have heard similar descriptions from other people who have both CBS and some dementia. Janet B. likes to listen to audiobooks and sometimes finds herself joined by a hallucinatory group of fellow listeners. They listen intently but never speak, do not respond to her questions, and seem unaware of her presence. At first, Janet realized that they were hallucinatory, but later, as her dementia advanced, she insisted that they were real. Once when her daughter was visiting and said, “Mom, there’s no one here,” she got angry and chased her daughter out.

A more complex delusional overlay occurred while she was listening to a favorite show on television. It seemed to Janet that the television crew had decided to use her apartment, and that it was set up with cables and cameras, that the show was actually being filmed at that moment in front of her. Her daughter happened to telephone her during the show, and Janet whispered, “I have to be quiet — they’re filming.” When her daughter arrived an hour later, Janet insisted that there were still cables all over the floor, adding, “Don’t you see that woman?”

Even though Janet was convinced of the reality of these hallucinations, they were entirely visual. People pointed, gestured, mouthed, but made no sound. Nor did she have any sense of personal involvement; she found herself in the midst of strange happenings, yet they seemed to have nothing to do with her. In this way they retained the typical character of CBS hallucinations, even though she insisted that they were real.

2. The Prisoner’s Cinema: Sensory Deprivation

The brain needs not only perceptual input but perceptual change, and the absence of change may cause not only lapses of arousal and attention but perceptual aberrations as well. Whether darkness and solitude is sought out by holy men in caves or forced upon prisoners in lightless dungeons, the deprivation of normal visual input can stimulate the inner eye instead, producing dreams, vivid imaginings, or hallucinations. There is even a special term for the trains of brilliantly colored and varied hallucinations which come to console or torment those kept in isolation or darkness: “the prisoner’s cinema.”

Total visual deprivation is not necessary to produce hallucinations — visual monotony can have much the same effect. Thus sailors have long reported seeing things (and perhaps hearing them, too) when they spent days gazing at a becalmed sea. It is similar for travelers riding across a featureless desert or polar explorers in a vast, unvarying icescape. Soon after World War II, such visions were recognized as a special hazard for high-altitude pilots flying for hours in an empty sky, and it is a danger for long-distance truckers focused for hours on an endless road. Pilots and truckers, those who monitor radar screens for hours on end — anyone with a visually monotonous task is susceptible to hallucinations. (Similarly, auditory monotony may lead to auditory hallucinations.)

In the early 1950s, researchers in Donald Hebb’s laboratory at McGill University designed the first experimental study of prolonged perceptual isolation, as they called it (the term “sensory deprivation” became popular later). William Bexton and his colleagues investigated this with fourteen college students immured in soundproof cubicles for several days (except for brief time out for eating and going to the toilet), wearing gloves and cardboard cuffs to reduce tactile sensation and translucent goggles which allowed only a perception of light and dark.

At first the test subjects tended to fall asleep, but then, on awakening, they became bored and craved stimulation — stimulation not available from the impoverished and monotonous environment they were in. And at this point, self-stimulation of various sorts began: mental games, counting, fantasies, and, sooner or later, visual hallucinations — usually a “march” of hallucinations from simple to complex, as Bexton et al. described:

In the simplest form the visual field, with the eyes closed, changed from dark to light colour; next in complexity were dots of light, lines, or simple geometrical patterns. All 14 subjects reported such imagery, and said it was a new experience to them. Still more complex forms consisted in “wall-paper patterns,” reported by 11 subjects, and isolated figures or objects, without background (e.g., a row of little yellow men with black caps on and their mouths open; a German helmet), reported by seven subjects. Finally, there were integrated scenes (e.g., a procession of squirrels with sacks over their shoulders marching “purposefully” across a snow field and out of the field of “vision”; prehistoric animals walking about in the jungle). Three of the 14 subjects reported such scenes, frequently including dreamlike distortions, with the figures often being described as “like cartoons.”