Interesting also the linked study on Psilocybin, which seems to decrease activity among brain hubs:
http://www.pnas.org/content/109/6/2138.full
"Psilocybin caused a significant decrease in the positive coupling between the mPFC and PCC. These results strongly imply that the subjective effects of psychedelic drugs are caused by decreased activity and connectivity in the brain's key connector hubs, enabling a state of unconstrained cognition."
