Scientists have found that psilocybin - a substance from "magic mushrooms" - does not turn brain activity into disordered noise, as was previously believed. On the contrary, under its influence brain activity becomes more ordered and adapts to what a person is doing and feeling at that moment. The results were published in the journal Nature.
The study involved 65 healthy adults aged 18 to 55 who had no prior experience taking psychedelics. Two dropped out before the experiment began, so 63 people received the standard dose of psilocybin (19 mg). Each underwent two visits: one without the drug and one with it. Participants underwent functional MRI (a method that shows which brain areas receive more blood) and electroencephalography (recording electrical waves of the brain via sensors on the scalp).
During scanning and EEG recording, the volunteers were in four different conditions: sitting with their eyes closed in silence, listening to a meditation, listening to emotional music, and watching a video of drifting clouds. This made it possible to test how the drug affects the brain at different levels of external stimulation.
It turned out that under psilocybin the overall connectivity of the brain is redistributed. When the eyes are closed, connections in sensory areas weaken - by up to 39% - while in associative areas (responsible for thinking) they strengthen - by up to 72%. When watching the video, on the contrary, both strengthen. In addition, the difference between the eyes-open and eyes-closed states in the visual system shrank by 85%: under the drug the brain seemed to begin to "see" even with the eyes closed.
The traditional measure of modularity - how clearly the brain divides into separate functional networks - decreased under psilocybin in all four conditions. However, these averaged data did not make it possible to predict what exactly the participants felt. The link to subjective experiences appeared only when using machine learning that tracked each person's activity over time.
The scientists trained an algorithm to recognize which of the four conditions a person was in from the pattern of their brain activity. Accuracy rose with the intensity of the experiences. In six participants with especially vivid effects, it rose from about 62% in the normal state to 98% under psilocybin. The stronger the experiences of unity and bliss, the better the classifier worked. No such link was found with anxiety or confusion of thinking.
The authors emphasize that this is a statistical association, not proven causality. They also note that the study was open-label - everyone knew they were receiving psilocybin rather than a placebo. This could have influenced the subjective reports. In addition, the conditions always followed in the same order, and the participants were healthy volunteers rather than patients with mental disorders. Therefore, the conclusions cannot yet be directly transferred to therapy.