Neurologist Oliver Sacks was called upon to help an elderly lady who had been visually impaired for 95 years and had begun to have hallucinations. Worried that she was becoming mad, the old woman called upon Oliver Sacks for help. She began to share details of her lucid hallucinations - most involving colors, moving shapes and deformed people or faces. Sacks began to explain to his patient that she was not going insane but that she was experiencing something called Charles Bonnet Syndrome, which was fairly common among the visually impaired. "About ten percent of the hearing impaired experience musical hallucinations and about ten percent of the visually impaired get visual hallucinations." (Oliver Sacks) Charles Bonnet Syndrome was identified in 1800, due to a grandfather who had poor vision and had begun to experience these sudden and rarely repetitive images. Sacks than elaborates during his presentation on how, when the faculties of vision have no or little input, they can become hyperactive and excitable causing these hallucinations. The brain is reacting to the limited availability of or the deficiency in images and tries to make sense of the images that each part of the brain is in charge of. About 10% of people experience this, but only 1% speak up because others are afraid to be called demented. .
Charles Bonnet Syndrome has different levels: geometrical, cartoons, and elaborate figures. FMRI have been used to recognize what parts of the brains are active while individuals are hallucinating, demonstrating that hallucinations are linked to the deterioration of vision. The primary visual cortex is used to perceive edges and patterns. Fuser Form gyros are used to form images such as faces, and the Infer Temple cortex is used to recognize figments or fragments. .
It is fascinating and yet petrifying how the brain functions. I cannot speak for anyone when it comes to hallucinations because I am not visually impaired and have not experienced mirages.
