Aspects of the Ethiology of Hallucinations

Hallucinations are misperceptions of things or events with one or more senses when an internal or external trigger doesn’t exist. They can be divided into visual, audioverbal, olfactorical, tactile and gustatory. Hallucinations develop due to 3 main pathophysiologicalmechanisms: psychophysiological, psychobiochemical (neurohormone dependent) and psychodynamic. Etiology of these perceptions consists of many things and is not always binned to psychiatric illnesses. These are some of the etiological factors which will be mentioned further bellow: psychosis, delirium, dementia, Charles Bonnet syndrome, Anton syndrome, seizures, migraine, Lhermitte syndrome, sleep disorders and “Alice in Wonderland” syndrome. Audioverbal hallucinations are thought to be a misperceptionof one’s own thoughts which are understood as the speech of someone else. This happens because of distorted function of frontotemporal efferents. These parts of brain are known for their sensorial region activation in the brain and also for the identification and perception of triggers that arise in a person. Furthermore, and increased activity of Wernicke’s region, right putamen, thalamus, and nucleus caudatus was also noticed. During the events of audioverbalhallucinations increased activity of Broca’s region and dorsal cortex of gyrus cinguli were noticed. Subcortical structures might also be the reason or the regulating part of the brain responsiblefor the manifestation of hallucinations which originate in the cortex. Visual hallucinations appear after triggering the primary or associational visual cortex, deafferetion mechanism, when there is some sort of damage to the periferial or central parts of nervous system responsible for visual perceptions. In addition, sleep and wakefulness cycles might be unbalanced and there can be some cognitive disorders.