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Biology 202, Spring 2005
Second Web Papers
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Hallucinations: What happened to external stimuli?

Nadia Khan

Hallucinations: What happened to external stimuli?

"...suddenly became strangely inebriated. The external world became changed as in a dream. Objects appeared to gain in relief; they assumed unusual dimensions; and colors became more glowing. Even self-perception and the sense of time were changed. When the eyes were closed, colored pictures flashed past in a quickly changing kaleidoscope. After a few hours, the not unpleasant inebriation, which had been experienced whilst I was fully conscious, disappeared. what had caused this condition?" -- Albert Hofmann- - Laboratory Notes (1943)

This was how Albert Hofmann sought to describe his experience taking lysergic acid diethylamide, commonly known as LSD or acid, for the first time. The hallucination is a phenomenon often solely associated with recreational drug use. It is described as a 'false and distorted sensory perceptions that appear to be real perceptions' (1). . These perceptions are mentally generated in the absence of a real external stimulus. Hallucinations feel like reality and can be felt, seen, tasted and even smelt.

Besides recreational drugs like mescaline, LSD and PCP (angel dust), hallucinations can stem from everyday experiences such as extreme sleep deprivation, prolonged stress and tension. In addition meditation can also cause hallucination by drawing on a memory of a past experience, lacking a physical stimulus. Neuro-electrical activity with a sensation involving touch, known as 'aura' can appear hallucinatory in the onset of a migraine and often as a warning of one. Individuals suffering from mental illnesses such as schizophrenia and bi-polar disorder also experience hallucinations as do patients of brain damage.

Besides aura, there are other mild hallucinations that we experience everyday including hypogognic hallucinations which are the sensation of falling just before going to sleep. Similarly, there are hypopompic hallucinations that occur as a person is just waking up from a state of sleeping.

Hallucinations do not have to be as severe in nature as a drug induced vision or someone suffering from paranoia hearing voices. There are some hallucinations that linked to the olfactory system. When surrounded by very strong smells such as burning rubber, melting sugar and feces, the nervous system creates the sensation of taste.

When we close our eyes and gently press out finger tips to the eyelids, we can experience a mild hallucination, reminiscent of those imagined during a drug induced perceptionary state. We see small illuminated geometric patterns like exploding stars, honey combs and spirals. Additionally, flickering lights can also cause mild hallucinations. This range of hallucinations has a mathematical pattern that can be examined and regulated by experts.

"Physiology and the way that images are mapped onto the brain's visual cortex play large roles in hallucinatory patterns, to be sure, but mathematics helps explain how instabilities in the brain arise and contribute to these patterns." (2).

It is unconfirmed as to whether the patterns arise as a result of the pressure exerted on the eyeball interfering with the retina's connection with the brain and visual images on the cortex, but when visual stimuli is completely cut off, the brain tries to compensate by creating perceptions based on experience.

In a sense, humans are constantly hallucinating when our vision compensates for the blind spot. We don't see the world with a gaping hole in it, but that is what out technical vision is. Instead we compensate for the gap but filling it in neurologically.

In the case of hallucinogenic drugs, hallucinations are created as a result of slowing down of inhibitory cells. Schizophrenic patients are hypothesized to see hallucination as a result of neurological confusion between 'external and internal stimulus source' (3). . They have also been attributed to the high levels of serotonin in patients of this disease. Schizophrenic visual hallucinations often occur in conjunction with auditory and olfactory hallucinations. It has also been hypothesized that a reduction in the size of frontal lobes could also be responsible for this occurrence. Patients of Charles Bonnet disease are in the process of becoming visually impaired and often completely blind. They are recognized by their strange content which shows hyper-imagination in the form of extremely vivid colors and pronounced images. Researchers wonder how patients who are lacking in sight can have hallucinations when they are obviously lacking in external visual stimuli but Dr. Pascual –Leone and his associates ran a test experiment blindfolding seeing individuals and found that after an extended period of time, these test subjects also started to experience hallucinations similar to those of patients of Charles-Bonnet disease. (4).

Hallucinations, as I said earlier, are a very complex phenomenon, largely because they are experienced in an altered state of normalcy. Therefore, studies and research is affected by this variable and scientists struggle to find a stable environment in which to study the neurobiology behind hallucinations. To a large extent, this reasoning is hypothetical because there are still no concrete linkage between changes in the brain and the imagining of external stimuli. However, there are some extremely viable theories behind the different types of hallucinations that we either hear about regularly or experience ourselves daily.

1. Transcranial Magnetic Stimulation Reduces Auditory Hallucinations by Kenneth J. Bender, Pharm.D., M.A. Psychiatric Times July 2000 Vol. XVII Issue 7
2. The roots of visual awareness :a festschrift in honour of Alan Cowey. Alan Cowey; Charles A Heywood; A D Milner; Colin Blakemore 2004 1st ed.
3. Voices in the Brain: The Cognitive Neuropsychiatry of Auditory Verbal Hallucinations Spence, Sean; David, Anthony S.
4. Pitt mathematician tracks origin of hallucinations Monday, August 02, 1999 By Byron Spice, Science Editor, Post-Gazette
6. Anti-angiogenesis Drug Improves Response to Radiation Therapy

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