Klaus Podoll and Derek Robinson, in their beautifully illustrated monograph
There may also be lexical hallucinations. Podoll and Robinson cite a case from the nineteenth-century literature:
A patient of Hoeflmayr’s saw words written in the air; a patient of Schob’s had hallucinations of letters, words, and numbers; and a patient reported by Fuller et al. “saw writing on the wall and when asked what it was said he was too far from it. He then walked up to the wall and was able to read it out clearly.”
Lilliputian hallucinations can occur in migraine (as well as in other conditions), as Siri Hustvedt described in a
I was lying in bed reading a book by Italo Svevo, and for some reason, looked down, and there they were: a small pink man and his pink ox, perhaps six
or seven inches high. They were perfectly made creatures and, except for their color, they looked very
All of these effects seem to show, by default, what a colossal and complicated achievement normal vision is, as the brain constructs a visual world in which color and movement and size and form and stability are all seamlessly meshed and integrated. I came to regard my own migraine experiences as a sort of spontaneous (and fortunately reversible) experiment of nature, a window into the nervous system—and I think this was one reason I decided to become a neurologist.
What is stirring up the visual system during a migraine attack, to provoke such hallucinations? William Gowers, writing more
than a century ago, when little was known of the cellular details of the visual cortex (or the brain’s electrical activity), addressed this question in
The process which gives rise to the sensory symptoms . . . of migraine is very mysterious. . . . There is a peculiar form of activity which seems to spread, like the ripples in a pond into which a stone is thrown. But the activity is slow, deliberate, occupying twenty minutes or so in passing through the centre affected. In the region through which the active ripple waves have passed, a state is left like molecular disturbance of the structures.
Gowers’s intuition proved quite accurate and was given physiological backing decades later, when it was discovered that a wave of electrical excitation could track across the cerebral cortex at much the same rate the fortifications did. In 1971, Whitman Richards suggested that the zigzag shape of migraine fortification patterns, with its characteristic angles, might reflect something equally constant in the architecture of the visual cortex itself—perhaps clusters of the orientation-sensitive neurons which Hubel and Wiesel had demonstrated in the early 1960s. As the wave of electrical excitation slowly marches across the cortex, Richards suggested, it might directly stimulate these clusters, causing the patient to “see” shimmering bars of light at different angles. But it was only with the use of magnetoencephalography, twenty years later, that it was possible to demonstrate that the passage of fortifications in a migraine aura was indeed accompanied by just such a wave of electrical excitation.
A hundred and fifty years ago, the astronomer Hubert Airy (who was a migraineur himself) felt that the aura of migraine provided “a sort of photograph” of the brain in action. He, like Gowers, may have been more literally accurate than he knew.
Heinrich Klüver, writing about mescal, remarked that the simple geometric hallucinations one might get with hallucinogenic drugs were identical to those found in migraine and many other conditions. Such geometrical forms, he felt, were not dependent on memory or personal experience or desire or imagination; they were built into the very architecture of the brain’s visual systems.
