I started having ocular migraines — all the visual hallucinations, none of the pain — while I was pregnant. I had another one this morning and started talking about it on Facebook with my Dad, from whom, apparently, I get this trait. Although we describe them differently — my conception of the auras as looking like undulating strips of tacky printed tights from American Apparel didn't really register with him — what we were describing to each other was pretty similar. And that, it turns out, is true across a wide spectrum of migraine sufferers. What we see is fairly uniform. What's more, descriptions and illustrations of migraine auras (especially those made by scientists for scientists) have contributed a great deal to our understanding of the mechanisms that make the hallucinations happen.
In 2007, the journal Brain published a paper by neurologist Geoffrey Schott about the role of art in taking a subjective phenomenon and turning it into something more like useful, objective information.
The image at the top of this article was drawn in 1941. It's in black and white, and the patterns it shows are, typically, in color, but other than that it's a pretty straightforward representation of the stuff I usually see when I have an ocular migraine. That pattern, which makes me think ugly, 80's-inspired clothing, was, to earlier eras, more evocative of defensive, medieval town walls. Because of that, it's called the fortification spectrum. It's such a common hallucination to see that its presence is almost diagnostic. You can see the fortification spectrum in illustrations dating back to the earliest known drawings of migraine hallucinations, which appeared in Scivias, an illuminated manuscript written by Hildegard of Bingen in 1180.
Here's the same fortification spectrum, again, as illustrated in 2000.
Schott's paper traces the history of how art became the driving force that changed the fortification spectrum from a personal hallucination to something scientists can study. And it shows how those illustrations eventually helped scientists begin to link the fortification spectrum (and migraines, in general) to a pattern of electrical stimulation and depression moving through the cerebral cortex. Think about it like a wave, with a crest where electrical impulses are stronger than normal, followed by a trough where they are lower than normal. Scientists call it CSD.
It was Lashley's illustrations of his migraine aura, however, and his conclusion concerning the speed of spread of the hallucination, that subsequently enabled Milner to more clearly envisage the possible link between CSD and migraine. In a prescient comment, he stated:
‘In brief, the writer thinks that attention should be drawn to the striking similarity between the time courses of scintillating scotomas and Leão's spreading depression because, if there is a true correspondence between these phenomena, there is hope that some of the work done on spreading depression can be brought to bear on the problem of migraine’ (Milner, 1958).
...This suggestion has been indirectly supported by numerous imaging techniques including xenon, SPECT and PET scanning, and MRI, and by magneto-encephalography (MEG) (Hadjikhani et al., 2001).