Increased spontaneous MEG signal diversity for psychoactive doses of ketamine, LSD and psilocybin.
Level 3 - non-randomized controlled study
Non-randomized or quasi-experimental within-subject pharmacological neuroimaging study
PubMed 28422113 · doi:10.1038/srep46421
What was done
Researchers computed neural signal diversity metrics (entropy and Lempel-Ziv complexity) on spontaneous magnetoencephalography (MEG) recordings from humans undergoing altered states of consciousness induced by psychoactive doses of three substances: psilocybin, ketamine, and LSD. The analyses controlled for spectral power changes and examined correlations between signal diversity and subjective ratings of psychedelic intensity.
What was found
Spontaneous MEG signal diversity was reliably higher across all three psychedelic conditions compared to normal waking rest, even after controlling for spectral changes. The abstract reports no numerical values, effect sizes, or confidence intervals. The increase was most pronounced for single-channel Lempel-Ziv complexity (reflecting temporal rather than spatial diversity) and correlated selectively with participant ratings of experience intensity.
Why it matters
Prior complexity measures consistently showed decreased signal diversity in lower conscious states (such as anesthesia or sleep); this study is the first to demonstrate neural signal diversity exceeding normal waking levels during psychedelic states.
Limits
The abstract omits key methodological details, including sample size (n), participant demographics, dosing protocols, presence or nature of placebo controls, and precise statistical values or effect sizes.
Cited by
- supports In studies published around 2017, administration of LSD, psilocybin, and psychedelic doses of ketamine was shown to increase brain entropy.
- supports States of reduced consciousness such as deep sleep, coma, or general anesthesia are characterized by low brain entropy and highly predictable ongoing brain activity.