The Induction of Klüver Visual Hallucinations

Determining the triggers, neurological, sensory or physical, for Blake’s ‘visions’ cannot be done with complete accuracy. In Blake’s case the absence of a diary, journal or an extensive written correspondence distances him from being a subject completely capable of full historical retro-diagnosis. Nevertheless, this chapter will discuss visual hallucinatory types in conjunction with a consideration of their likely agencies of induction since some of them may have had a historical specificity unlikely to be paralleled today. It should be remembered throughout that ‘Hallucinations in psychologically normal individuals provide a valuable route to studying the neural mechanisms of visual awareness.’ The natural agency of ‘Scheerer’s phenomena’ has been discussed in Chap. 1 along with Munro Smith’s assigning of migraine aura to some of Blake’s images in 1909. Naturally occurring agencies may also include some triggers of migraine, such as photophobia, which appear to be reported by Blake’s contemporaries J.T. Smith and Allan Cunningham (both of whom, of course, would not have been able to access a vocabulary capable of arriving at a diagnosis of migraine). William may also have indulged in the popular contemporary electrical therapies known to have been used by Catherine Blake, c. 1800–1804. Finally, this chapter will discuss hallucinations caused by prolonged exposure to engraved lines on copper plates or the prints taken from them (‘Parallellinienfeld in einem Kupferstiche’), a method of induction used during the first scientifically recognized experiments recording visual hallucinations. Unsurprisingly, such methods of induction have long been superseded and forgotten much like the trade of copper-plate engraver that Blake followed.