10. Something about visual movement or “optic flow” seems to be especially provocative of visual hallucinations in people with CBS or other disorders. I met one elderly psychiatrist with macular degeneration who had experienced only a single episode of CBS hallucinations: he was being driven in a car and began to see, on the edges of the parkway, elaborate eighteenth-century gardens which reminded him of Versailles. He enjoyed the experience and found it much more interesting than the ordinary view of the roadside.
Ivy L., who also has macular degeneration, wrote:
As a passenger in cars, I began riding with my eyes closed. Now I often “see” a small, moving travel scene in front of me when my eyes are shut. I “see” open roads and sky, houses, and gardens. I do not “see” any people or vehicles. The scene constantly changes, showing unidentifiable houses in great detail sliding by when the car is in motion. These hallucinations never appear except when I am in a moving car.
(Mrs. L. also reported text hallucinations as part of her CBS, “brief periods when I would ‘see’ handwriting in huge letters across a large white wall, or the income tax figures imprinted on the drapes. These lasted several years, at intervals.”)
11. Such correlations involve sizable regions of the brain; they are at a macro level. Correlations on a micro level, at least for elementary geometric hallucinations, have been proposed by William Burke, a neurophysiologist who has experienced such hallucinations himself, due to macular “holes” in both eyes. He has been able to estimate the visual angles subtended by specific hallucinations and to extrapolate these into cortical distances. He concludes that the separation of his brickwork hallucinations corresponds to the separation of the physiologically active “stripes” in the V2 part of the visual cortex, while the separation of the dots he hallucinates corresponds to that of the “blobs” in the primary visual cortex. Burke hypothesizes that with diminished input from his damaged maculas, there is diminished activity in the macular cortex, releasing spontaneous activity in the cortical stripes and blobs that give rise to hallucinations.
12. 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.
13. While the romantic use of sensory deprivation, as that of vision-producing drugs, has diminished since the 1960s, its political use is still horrifyingly common in the treatment of prisoners. In a 1984 paper on “hostage hallucinations,” Ronald K. Siegel pointed out that such hallucinations can be magnified sometimes to madness, especially when combined with social isolation, sleep deprivation, hunger, thirst, torture, or the threat of death.
14. There may be severe visual impairment or complete blindness without a hint of CBS, and this might seem to imply that visual deprivation alone is not a sufficient cause for it. But we are still ignorant as to why some people with visual problems get CBS and others do not.
15. Molly Birnbaum, an aspiring chef who became anosmic after being struck by a car, has described the anosmic’s predicament eloquently in
her memoir
