Half of the participants ranked their session among the most meaningful experiences of their lives, and 24 put it in their personal top five. Stolkier and his colleagues started analyzing their brain scan data to find out why.

Blurred boundaries

Measuring global functional connectivity—how much influence each patch of cortex exerts over the rest—the team found that, when participants had their eyes closed, sensory regions lost sway while associative regions gained. “It seems like the brain’s ability to construct reality, or imagination, or our associations, our beliefs, our sense of self—these faculties had more dominance over sensory areas,” Stoliker says, stressing that the interpretation is a hypothetical. “This could help explain why people have meaningful, complex imagery experiences, why they have mystical experiences with imagery that is personally relevant to them.”

Another observation the team made was that connections within each brain network weakened, connections between networks strengthened. The brain’s modularity, a parameter that describes how cleanly neurons stay sorted into specialist teams, dropped across all four parts of the experimental sequence.

What’s more, researchers found that, when sober, activity in a brain with its eyes shut looked very different from a brain watching a movie. Under psilocybin, that difference nearly evaporated. In the visual network, the gap between eyes-open and eyes-closed connectivity shrank by 85 percent. The results from the EEG session independently confirmed that, with alpha-band activity (normally a marker of the brain gating visual input) reduced by nearly half.

“When somebody takes a psychedelic and they’re able to close their eyes and see complex imagery, there seems to be less boundary between the internal and external world than we ordinarily experience,” Stoliker says.

Regardless of these details, the results rather accurately reproduced the chaos in the brain so many researchers claimed psychedelics caused. This chaos, though, turned into order when the team processed their data in a slightly unorthodox way.

Hidden order

Scientists usually do two acts of averaging in a standard brain imaging study. The first is averaging over time. An eight-minute brain scan comprises a few hundred successive images of the whole brain. To understand how two specific regions work together, researchers conventionally average all these images down to a single number describing how well the two regions’ activity matched up across the whole eight minutes.