Manipulating Visual Cortex to Induce Hallucinations

fromTerence McKenna - Ayahuasca StoriesWhat is a hallucination? The question seems simple enough. “Ahallucination is a perception in the absence of external stimulus that has qualities of real perception. Hallucinations are vivid, substantial, and are perceived to be located in external objective space. ” When we think of visual hallucinations, we often think of trippy colorful images induced by psychedelic drugs (hallucinogens).Aredreams hallucinations? How about visualimagery? Opticalillusions of motion from viewing a non-moving pattern? No, no, and no (according to this narrow definition). Hallucinations are subjective and inaccessible to others, much as my recent posts discussed thepresence or absence of visual imagery in individual humans. However, people can tell us what they ' re seeing (unlike animals).Visual hallucinations can occur inpsychotic disorders such as schizophrenia and schizoaffective disorder, although auditory hallucinations are more common in those conditions. Visual hallucinations are more often associated with neurodegenerative disorders. Among patients withParkinson ' s Disease, 33% to 75% experience visual hallucinations, usually related to dopaminergic or anticholinergic drug therapy.In contrast, hallucinations indementia with Lewy Bodies (DLB) are diagnostic of the disease, and not related to pharmacological treatment.  “Recurrent complex visual hallucinations ... are typically well-formed, often consisting of figures, such as people or...
Source: The Neurocritic - Category: Neuroscience Authors: Source Type: blogs