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Almost three-quarters of a century after chemist Albert Hofmann accidentally ingested LSD and experienced its mind-expanding effects, brain imaging has given researchers their first glimpse of how it causes its profound effects on consciousness.
One of the most notable aspects of the psychedelic experience is a phenomenon known as the dissolution of the ego, in which users feel somehow detached from themselves. Studying how the normally stable sense of self gets disrupted can tell us how neural mechanisms create this integral part of the human experience.
“This is why psychedelics in general but also LSD are special. They really alter consciousness in this fundamental way and therefore they are very powerful tools to understand the nature of consciousness,” says Robin Carhart-Harris of Imperial College London, who carried out the new study.
The team gave 20 volunteers infusions on two days, once containing 75 micrograms of LSD, the other a placebo. Then volunteers lay in a scanner and had their brains imaged with three different techniques, which together built up a comprehensive picture of neural activity, both with the drug and without.
MRI scans showed that LSD caused brain activity to become less coordinated in regions that make up what is called the default mode network. The size of the effect was correlated with participants’ ratings of their own ego dissolution, suggesting that this network underlies a stable sense of self.
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