Before Christmas I had the pleasure of reading Oliver Sacks’s new book Hallucinations.
Like his other books, this is extremely readable with vivid accounts of his patients’ symptoms leading to a tentative neurological explanation of their often bizarre experiences. In this case I was pleased to find that I had myself experienced a common form of visual hallucination. A few years ago I fell (in trying to catch a frisbee sailing away from my hand) and banged the back of my head. Shortly afterwards half my visual field was filled with wobbly black and white hexagons. I realized I could not drive home with these patterns blocking out half the motorway. By the next day they had gone but in the weeks following I occasionally had the illusion of a large red hexagon taking over my visual field.
A common form of auditory hallucination is tinnitus, which friends of mine suffer from – that is, a buzzing or ringing in the ear, which is produced by the nervous system not by outside sounds.
Oliver Sacks’s patients had much more sensational hallucinations – visual, auditory and olfactory. He devotes chapters to hallucinations associated with blindness, deafness, migraine, epilepsy, the periods before and after sleep etc. What they have in common is that they are produced by the perceptual pathways in the brain, not by the different ones with which we voluntarily imagine things. MRI scanning provides the evidence for this fact. The person has no control over hallucinations and is not usually upset by them. My own modest experience confirms this – I found them merely irrelevant and irritating.
What I found most interesting is that the more sensational hallucinations – of people in strange costumes, the images multiplying, the bright colours, distorted faces, people and things getting larger and smaller – correspond to the universal figures of folklore. It is clear that the giants and dwarfs, the monsters and fairies of our traditional tales are the product of blips in the neurological pathways through which we see, hear and smell the world. Sacks makes reference to Lewis Carroll, who suffered from migraine, which can produce hallucinations.
The connection between creativity and neurological irregularities is fascinating and I look forward to pursuing the question through other neurological texts.