In a brain scan study analyzing global functional connectivity under psilocybin, researchers found that while subjective psychedelic experiences often feel like sheer chaos, underlying neural networks actually undergo a structured shift in dominance away from sensory regions and toward associative networks.
Global Functional Connectivity Shifts Away From Sensory Regions
Half of the participants in the study ranked their session among the most meaningful experiences of their lives, with 24 placing it in their personal top five. To find out why, Stoliker and his colleagues analyzed brain scan data by measuring global functional connectivity—quantifying how much influence each patch of cortex exerts over the rest of the brain.
When participants had their eyes closed, sensory regions lost sway while associative regions gained influence. Stoliker noted that the brain’s ability to construct reality, imagination, associations, beliefs, and a sense of self gains more dominance over sensory areas during these sessions.
That shift helps explain why people report meaningful, complex imagery experiences. It sheds light on why users undergo mystical experiences with imagery personally relevant to them. However, Stoliker stresses that this interpretation remains strictly hypothetical.
Network Modularity Drops Across Experimental Sequences
Another key observation from the team involved network-level connectivity changes. Connections within each distinct brain network weakened, while connections between different networks strengthened significantly.
Modularity—a parameter describing how cleanly neurons stay sorted into specialist teams—dropped across all four parts of the experimental sequence. When sober, activity in a brain with its eyes shut looked starkly 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.
Independent confirmation came from simultaneous EEG sessions. These recordings showed that alpha-band activity, normally a biological marker of the brain gating visual input, was 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.
Unorthodox Data Processing Uncovers Hidden Order
These results accurately reproduced the neurological chaos that many previous researchers claimed psychedelics caused. Yet that apparent chaos transformed into order when the team processed their imaging data using an unorthodox methodology.
Scientists conventionally perform 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 normally average all these images down to a single number describing how well the two regions matched up across the entire eight minutes.
