One participant described "melding with the MRI machine, floor, walls and air". Another described "losing all sense of self", becoming at one with their surroundings. Half the participants in our study reported having one of the most meaningful experiences of their lives.
Authors
- Devon Stoliker
Turner Impact Fellow, Monash University
- Adeel Razi
Professor of Computational Neuroscience, Monash University
What were they talking about? Taking psilocybin, the psychedelic compound in magic mushrooms.
Participants reported feeling less separation between themselves and world. We scanned their brains during the experience, and found surprising patterns of organisation - while the brain networks that process our inner world and surroundings also became less distinct.
Our research is published today in Nature. It adds new information to the ongoing discussion of the mental effects of psychedelics such as psilocybin and how they can be used in therapies .
Rest, meditation, music and clouds
We examined 62 healthy adults with no prior psychedelic experience. Each received 19 milligrams of psilocybin, a moderate dose similar to those used in clinical trials.
Participants had magnetic resonance imaging (MRI) scans and electroencephalograph (EEG) recordings of electrical brain activity twice, about one week apart. Once without psilocybin, and once after taking it. Both sessions involved rest, meditation and listening to ambient, ethereal music with closed eyes, followed by a silent video of moving clouds.
We have published the results in the PsiConnect dataset . It is the world's largest single-site psychedelic brain-imaging dataset and is openly available .
Less difference between eyes open and eyes closed
In ordinary consciousness, closing our eyes reduces external visual input. Under psilocybin, however, participants can have complex visual experiences.
Using MRI and EEG analyses conducted by our co-author Leonardo Novelli , we found this separation was reduced across participants.
In the MRI scans, the gap between eyes-open and eyes-closed activity shrank by 85% in the visual network, and by more than 66% across all brain networks. In the EEG recordings, the difference in a major brain rhythm between eyes-open and eyes-closed states decreased by 48%.
Regions involved in integrating information, including the regions involved in the sense of self, became more connected with the rest of the brain. Sensory regions became less connected, but this varied by participant.
Hidden organisation
Previous research has found that psilocybin desynchronises the coordinated activity of brain networks . We also saw disruption. However, this does not explain why some individuals experience clarity during the psychedelic state or report subsequent positive psychological changes.
Most studies average brain activity across time. This can conceal how it changes from moment to moment.
Our analytical strategy was to use machine learning to find patterns in complex brain activity. Our co-author Moein Khajehnejad applied a machine-learning method that made a simplified map of complex brain activity while still tracking how it changed over time.
We used this map to examine participants with and without psilocybin during rest, meditation, music and cloud-watching. In the simpler map, those four contexts formed distinct patterns.
Continuity between the self and world
The signature of this organisation was clearest when participants reported less separation between themselves and the world that was positively felt. It was weaker for visual or sensory effects alone, and absent when participants reported confusion and anxiety.
We call the experience associated with this organisation "embeddedness". Participants felt continuous with their moment-to-moment experiences, including the music and their surroundings, rather than separate from them.
The signature was also associated with reports of positive psychological change the next day. This helps explain why the psychedelic experience can be meaningful or therapeutic despite earlier analyses suggesting the brain is disordered.
The importance of context
Half the participants were assigned to an eight-week standardised mindfulness course. At the group level, their reported experiences and brain changes did not measurably differ from those of the other participants.
When we looked at the experience of listening to music, however, participants rated it as substantially more meaningful and emotionally resonant under psilocybin than without it.
The signature may provide part of the biological explanation for why context is so influential during the psychedelic experience. It could allow researchers to track how the brain responds to different contexts, while providing a target for patient preparation and session design.
Future studies can test whether the signature appears in patients, how preparation and setting influence it, and whether it can help predict who benefits from treatment.
Limitations
Our study participants were healthy adults, not patients. The study was open-label, meaning there was no placebo group. Everybody knew they had taken psilocybin.
Responses varied widely, despite the fixed dose. We cannot yet say which setting or stimulus is best, whether the signature generalises to patients or whether it predicts treatment benefit.
Adeel Razi receives funding from Australian Research Council, National Health Medical Research Council, Canadian Institute for Advanced Research and Wellcome Leap.
Devon Stoliker does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.
