After injecting 20 mentally and physically healthy people either with 75 micrograms of LSD each or a placebo, hooking them up to a brain scan for 75 minutes, and asking them to close their eyes, researchers discovered that volunteers on the hallucinogenic actually showed evidence of increased activity in the primary visual cortex—the region of the brain linked with sight. This suggests that LSD users (who, remember, had their eyes shut) were “seeing” without actually seeing.
The study’s lead neuroscientist Robin Carhart-Harris from Imperial College London explained that this basically offers a biological perspective on what a trip really looks like, suggesting that study volunteers were “seeing with their eyes shut.… [T]hey were seeing things from their imagination rather than from the outside world,” he said in a statement.
Also of note: Volunteers on the drug showed increased activity across the entire brain, with areas actually working in tandem that wouldn’t under typical circumstances, which researchers could say explain the drug-induced phenomenon of hallucination.
“We found that under LSD, compared to placebo, disparate regions in the brain communicate with each other when they don’t normally do so,” David Nutt, a coauthor on the study, explained to Nature.
Nutt also explained that this finding explains the “ego dissolution” people experience on LSD—the feeling that you are melded with people and things around you, and your consciousness is bigger than just yourself. “Within some important brain networks, such as the neuronal networks that normally fire together when the brain is at rest, sometimes called the ‘default mode network,’ we saw reduced blood flow … and that neurons that normally fire together lost synchronization. That correlated with our volunteers reporting a disintegration of their sense of self, or ego. This known effect is called ‘ego dissolution’: the sense that you are less a singular entity, and more melded with people and things around you.”
A separate study that was led by one of the authors of this paper also shows—unsurprisingly—music enhances the effects of LSD. It discovered that unless you’re listening to music (Pink Floyd, perhaps?), LSD will weaken communication between the part of the brain associated with memory (the parahippocampus) and the visual cortex. However, if you’re listening to tunes while tripping, “the visual cortex receives more information from the parahippocampus, and this is associated with increases in eyes-closed imagery and personal memories,” Nutt explained to Nature.
The reason it’s taken so long for us to have this kind of insight into the effects of psychedelics is research on humans using LSD in the US has been banned since the 1960s for obvious reasons. However, this particular study was carried out in the UK, where it’s not outlawed, but highly expensive to acquire the licenses needed.
This brain scan image from the study outlines its findings pretty simply—trippy, right?