The researchers ended up with 15 clear datasets, the rest discarded due to movement-related noise, and what they found offers insight into the brain mechanisms behind two definitive aspects of the psychedelic experience: visual hallucinations and effects on consciousness, and particularly what's known as "ego dissolution" or a breakdown of the sense of self as it's usually understood.Carhart-Harris highlighted the effects on consciousness as particularly interesting. "Really, I think this is why psychedelics in general, but also LSD, are special," he said. "They really alter consciousness in this very fundamental and unusual, novel way, and therefore they're very powerful tools to understand this major problem of 'what is the nature of consciousness?'"The study revealed several interesting leads. In fMRI scans of subjects' brains on LSD, researchers found reduced communication between the parahippocampus and regions related to the sense of self such as the retrosplenial cortex. "There's a kind of dislocation, if you want, in this circuit, and a disintegration in the system which underlies these functions," explained Carhart-Harris. Most importantly, the magnitude of this observed pattern correlated with subjects' ratings of the ego-dissolution effect.In their paper, the researchers compare their overview of results with studies on other psychedelics, such as psilocybin. "It seems increasingly evident that psychedelics reduce the stability and integrity of well-established brain networks and simultaneously reduce the degree of separateness or segregation between them; that is, they induce network disintegration and desegregation," they write. Carhart-Harris explained this as the brain being less "compartmentalized" and more "unified" under psychedelics, functioning in a "simpler" or "freer" way. In the paper, he and his coauthors characterizes this phenomenon as brain activity becoming more "entropic."
"[Psychedelics] are very powerful tools to understand this major problem of 'what is the nature of consciousness?'"
For her part, Feilding characterised the groundbreaking study as a "coming-of-age" of Hoffman's discovery. "But for the taboo surrounding this field, he would, surely, have won the Nobel Prize," she said.She spoke of her own use of LSD after being introduced to it in the 60s, and her enduring aim "to re-integrate these valuable compounds into the fabric of society, and to make their benefits available where appropriate."There are of course many unanswered questions remaining, and the researchers are working on other studies with psychedelics, the most imminent being a clinical trial looking at the effects of psilocybin (magic mushrooms) in depressed patients.It's worth noting this was a small trial, and only involved participants who had previously used psychedelics, which could impact the results. Carhart-Harris also pointed out that it's difficult to measure things like ego dissolution, which is highly subjective.However, the team hopes that publishing this study will help open the floodgates for further research. Having published their findings in a highly-regarded journal and presented them in the eminent surroundings of the Royal Society, they want to push the impression that psychedelics research is not a fringe interest but a mainstream concern."I think we've now achieved something that, hopefully, is transformational," said Nutt. "If you want to quote this, I will say to you that this, for human neuroscience, is the same as the discovery of the Higgs boson, because we have known for almost as long as we knew there was a Higgs boson that we needed to study the effects of LSD on the brain, but no one did it because the reputational risk was too oppressive.""We've done it, we've discovered remarkable insights, and now there is no reason for others not to do it."
"I will say to you that this, for human neuroscience, is the same as the discovery of the Higgs boson"