The psychedelic drug LSD replaces one illusion with another in the brains of those who take it, finds a new study that helps explain why people high on LSD can lose their sense of self.
The research, published in the journal Current Biology, represents the first detailed investigation on how LSD - the crystalline compound lysergic acid diethylamide - changes brain function.
"There is ‘objective reality' and then there is ‘our reality,'" co-author Enzo Tagliazucchi of the Amsterdam-based Royal Netherlands Academy of Arts and Sciences said in a press release.
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"Psychedelic drugs can distort our reality and result in perceptual illusions. But the reality we experience during ordinary wakefulness is also, to a large extent, an illusion."
How our sense of vision works provides just one example of this.
"We know that the brain fills in visual information when suddenly missing, that veins in front of the retina are filtered out and not perceived, and that the brain stabilizes our visual perception in spite of constant eye movements," Tagliazucchi explained. "So when we take psychedelics we are, it could be said, replacing one illusion by another illusion. This might be difficult to grasp, but our study shows that the sense of self or ‘ego' could also be part of this illusion."
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Tagliazucchi, Robin Carhart-Harris of Imperial College London, and their colleagues scanned the brains of 15 healthy people while they were on LSD versus a placebo.
The scientists discovered that LSD inflated the level of communication between normally distinct brain networks. The higher the test subjects became, the more they reported a sense of ego dissolution.
The researchers linked this feeling to increased global connectivity within the individuals' frontoparietal cortex, which is a brain region associated with self-consciousness. They noted, in particular, increased connection between this portion of the brain and sensory areas that are in charge of receiving information about the world around us and conveying it for further processing to other brain areas.
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"This could mean that LSD results in a stronger sharing of information between regions, enforcing a stronger link between our sense of self and the sense of the environment and potentially diluting the boundaries of our individuality," Tagliazucchi said.
He and his team also observed changes in the functioning of a part of the brain previously linked to "out-of-body" experiences, in which people feel as though they have left their bodies. Other drugs, such as ketamine and PCP, can create such sensations in users too, with some people even having near-death sensations.
These drugs can be highly addictive, with clear associated dangers. The jury is still out, however, on whether frequent usage of drugs like LSD can directly cause brain damage - resulting in mental disorders such as schizophrenia - or whether the drugs just intensify symptoms within those already afflicted with one or more mental illnesses.
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Tagliazucchi believes that psychedelic drugs have value to science when administered in controlled research settings.
He next plans to use neuroimaging to explore various states of consciousness, including sleep, anesthesia, and coma. He additionally hopes to make direct comparisons between people in a dream versus a psychedelic state.
Imperial College London researchers are also investigating other psychedelic drugs and their potential use in the treatment of disorders. These include depression and anxiety.