Hallucination

"For our ancestors, dreams, hallucinations, revelations, and cock-and-bull stories were inextricably mixed with facts."

"All at once, and without further warning, my reason forsook me altogether, and I started from Dr. Moffitts house to go to my boarding place. The sidewalks were to me one mass of living, moving, howling, and ferocious animals. Bears, lions, tigers, wolves, jaguars, leopards, pumas—all wild beasts of all climes—were frothing at the mouth around me and striving to get to me. Recollect that while all this was hallucination it was just as real as if it had been an undeniable and awful reality. Above and all around me I heard screams and threatening voices. At every step I fell over or against some furious animal. When I finally reached the door leading to my room and just as I was about to enter, a human corpse sprang into the doorway."

"If the reverse learning mechanism we have postulated exists, one might wonder what effects its failure might have. A complete failure might lead to such grave disturbances—a state of almost perpetual obsession or spurious, hallucinatory associations—that it would probably be severely selected against. A partial failure should produce unwanted responses to random noise, perhaps as hallucinations, delusions, and obsessions, and produce a state not unlike some schizophrenias."

"The simplest migraine hallucinations, as we have said, are phosphenes—simple, almost structureless, moving lights in the visual field. Phosphenes virtually identical to these are readily elicited by direct electrical stimulation of the visual cortex, either in the primary area (Brodmann area 17) or the surrounding visual association cortex."