Hallucinations
by Oliver Sacks
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Introduction
Hallucinations used to not have a proper definition. It's hard to differentiate between illusion, misperception and hallucination. Perceptions that can't be shared with others are hallucinations. If you see something that isn't there. To the person hallucinating they can seem perfectly real.
Hallucinations might play a role in the origin of our folklore and cultures. And all cultures have found hallucinogens which they use for religious practices throughout.
Hallucinations share characteristics with dreams but they are a different and distinct phenomenon.
Hallucination is a unique and special category of consciousness and mental life.
Hallucinations are a part of being human. They are in a way "normal" brain states.
Chapter 1 - Silent Multitudes: Charles Bonnet Syndrome
Book Recommendation: Mindsight – Colin McGinn
Blind people can hallucinate. In Hallucinations the eyes tend to move around because one expects novel things. It's not like the minds eye.
Book Recommendation: Essay Concerning Human Understanding – John Locke
Book Recommendation: Disturbances of the Mind – Dozer Draaisma
With Charles Bonnet Syndrome people see things but only for some time, then those visions disappear again. Stress seems to cause it somehow. It's mostly in people with impaired vision.
Book Recommendation: Remembrance of Things Past – Proust
Hallucinations are usually not taken as real for long. People more often have simple hallucinations, like shapes or colors, maybe text, complex scenes are rarer.
Brain scans correlate the type of hallucinations to activity in the brain areas that are normally associated with vision that "produce" this type of stimulus. Colors with color areas, faces with face areas of the brain and so on.
The mind can't tell apart visions from reality. Because they come down the same neurons.
Hallucinations make use of the same pathways as perception itself.
Memories can influence and alter hallucinations.
People might have "proto-objects" or "proto-images" as part of their visual systems, little "images" that make up bigger more complicated scenes. And these building blocks are learned from experience.
Text and musical hallucinations are also not properly formed. They are like the things, but not quite exactly.
Book Recommendation: Interpretation of Dreams – Freud
Hallucinations can be dangerous but most of the time they are almost friendly, like the broken eyes trying to still do their job, even though they can't. People lose their primary visual world and gain a secondary visual, hallucinatory world instead.