"When your brain works well, your frontal lobe is the driver of the car it decides what's going to happen and is in control of the rest of the brain," she said. She said factors including lack of sleep, stress, grief, and trauma could make the brain more vulnerable to hallucinations by upsetting the relationship between the sensory cortex and the frontal lobe. Professor Waters' best guess is that "everyday" hallucinations may share common mechanisms with more serious hallucinations. And what makes a hallucination distressing in some situations and not in others?" "We're still trying to understand whether there are different forms of hallucinations or whether there is only one type that takes different shapes. "In the past 100 years it's always been about schizophrenia in the past couple of years we've suddenly ramped up investigations outside of schizophrenia," she said. Research into this kind of hallucination is in its very early days, said Professor Waters. In some cultures it's acceptable, for example, to hear the voices of your dead relatives. This includes hearing their name being called, the phone ringing or seeing someone sitting at the end of their bed. Hallucinations aren't always intrusive, negative and scary, even in conditions like schizophrenia.Ībout 70 per cent of healthy people experience benign hallucinations when they are falling asleep, said Professor Waters. Almost two out of three people have benign hallucinations The big question is whether the same kind of processes are responsible for less extreme hallucinations. "It allows the processing of images and sound that would normally be inhibited," she said. Psychoactive drugs could also upset the relationship between the sense processing parts of the brain and the frontal lobe in a similar way, said Professor Waters. Similarly, people with Parkinson's disease appear to have an overactive visual cortex, which results in images being generated in their brain of things that aren't actually there. This results in random sounds and speech fragments being generated. One major theory is that hallucinations are caused when something goes wrong in the relationship between the brain's frontal lobe and the sensory cortex, said neuropsychologist Professor Flavie Waters from the University of Western Australia.įor example, research suggests auditory hallucinations experienced by people with schizophrenia involve an overactive auditory cortex, the part of the brain that processes sound, said Professor Waters. Normally our brain is good at distinguishing between a sound or image that is occurring in the outside world, and one that is just a product of our mind. alcohol withdrawal i.e.We're still trying to understand whether there are different forms of hallucinations or whether there is only one type that takes different shapes.hallucinogens: mescaline, psilocybin, lysergic acid diethylamide (LSD), phencyclidine (PCP), ecstasy (MDMA), atropine, dopamine agonists.sleep-related, especially in narcolepsy.peduncular hallucinosis: due to infarcts of the midbrain.Creutzfeldt-Jakob disease (CJD): particularly the Heidenhain variant.Parkinson disease dementia: 50% experience visual hallucinations.Lewy body dementia: >20% experience visual hallucinations.migraine, posterior reversible encephalopathy syndrome (PRES).Anton syndrome: may be seen after occipital infarcts.tumors, vascular malformations, strokes, epileptogenic foci) psychoses ( schizophrenia, schizoaffective disorder).delirium including secondary to drugs such as cocaine, methamphetamine.Pathology EtiologyĪ number of conditions are known to be associated with visual hallucinations including: In other settings, for example those due to psychiatric disturbance, delirium or intoxication/withdrawal are often frightening. In some cases, such as Lilliputian hallucinations (miniature people in lines or groups often performing strange actions), the hallucinations are not distressing, but rather elicit curiosity or wonder. Of interest, the patient's insight and response to these hallucinations is variable. complex scenes often associated with sensory distortions.flashes of light and color or indistinct forms.typically due to irritation or stimulation of the primary visual cortex (e.g.They can be divided into simple and complex forms: Visual hallucinations can take various forms and should be distinguished from visual distortions or pseudohallucinations. The use of the term organic here is by convention, and should not be taken to imply absence of brain dysfunction in psychiatric illness. Visual hallucinations are relatively uncommon, and can be due to a variety of 'organic' brain diseases, affecting a variety of regions of the brain.
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