"For all three", - they're referring to the aforementioned trio of psychedelics - "we find reliably higher spontaneous signal diversity, even when controlling for spectral changes", the researchers write in the paper, noting that this is the first time that these measurements have been applied to these drugs and "yielded values exceeding those of normal waking consciousness".
"People tend to associate phrases like "a higher state of consciousness" with hippy speak and mystical nonsense".
Most people would agree that they are more conscious when fully awake, less conscious at various stages of sleep, and least conscious when under forms of anesthesia that suppress brain activity.
This measure of the complexity of brain activity - called neural signal diversity - provides an index of the level of someone's consciousness.
"People often say they experience insight under these drugs - and when this occurs in a therapeutic context, it can predict positive outcomes".
This new study set out to determine how a psychedelic state would compare to other levels of wakefulness and unconsciousness, according to a scale of brain signal diversity measured by monitoring the magnetic fields produced by the brain.
The work was recently conducted by researchers with London's University of Sussex and Imperial College, where volunteers were given doses of either placebo or psychedelic drugs like psilocybin ('magic mushrooms'), LSD, or ketamine.
For the study, the team from University of Sussex and Imperial College, London measured the activity of neurons in people's brains shortly after they were administered a psychedelic drug.
Dr Suresh Muthukumaraswamy, from the University of Auckland, who was involved in all three initial studies, commented: "That similar changes in signal diversity were found for all three drugs, despite their quite different pharmacology, is both very striking and also reassuring that the results are robust and repeatable".
More sophisticated and varied models are needed to confirm the results, but the scientists are "cautiously excited" about the potential use of their findings in discussions around using psychedelics medically, for example in treating depression.
It's also interesting to note that although ketamine, LSD, and psilocybin have different pharmaceutical mechanisms of action, a clear similarity in the cortical localization of changes in signal diversity was reported.
"The present findings may help us understand how this can happen". "This suggests that our measure has close links not only to global brain changes induced by the drugs, but to those aspects of brain dynamics that underlie specific aspects of conscious experience". For now, however, researchers at the Sussex University in the United Kingdom just wanted to see what effect these drugs have on our brain.
The subjects had all tried psychedelics in the past, and reported experiences during the study that likely sound familiar to other users (seeing geometric patterns, experiencing vivid imaginations, having feelings of merging with the surroundings, and getting senses mixed).