Dominic H ffytche "The Hallucinating Brain"

Hallucinations are caused by activity in the brain and contribute to conscious experience. The brain activity thus correlates with consciousness although the exact nature of this relationship is open to interpretation. What is more certain is that the brain activity helps determine what hallucinations are and what they are not, in a way inaccessible to subjective experience. In this talk I dispel a number of common misconceptions using evidence derived from the visual domain (summarised in ffytche, 2005; ffytche, 2007). On philosophical and phenomenological grounds, hallucinations seem different to normal percepts, illusions and afterimages but similar to imagery; the opposite of what brain activity reveals. Similarly, it seems obvious that, as stored representations, hallucinations are reactivated memories; yet brain activity tells us otherwise. The presence or absence of understanding and recognition have long been used to distinguish hallucinations from related phenomena but do not seem to influence the brain activity underlying a hallucination. Finally, hallucinations that appear phenomenologically identical can have entirely different neurobiologies. I conclude that a single neurophilosophical account of hallucinations will not suffice - we may need a family of theories.

ffytche DH. Visual hallucinations and the Charles Bonnet Syndrome. Current Psychiatry Reports 2005; 7: 168-179.

ffytche DH. Visual hallucinatory syndromes: past, present, and future. Dialogues Clin Neurosci 2007; 9: 173-89.