Department of Anesthesiology and Critical Care, Neuroscience of Unconsciousness and Reanimation Research Alliance (NEURRAL), University of Pennsylvania, Philadelphia, United States.
2 papers in the library · 20 citations · publishing 2023-2025
A systematic review of 91 fMRI studies on acute psychedelic effects found substantial methodological heterogeneity. Only 51 unique samples were used across the 91 papers, and 54% of studies did not meet current standards for correcting Type I errors or controlling motion artifacts. Psilocybin and LSD consistently modulated connectivity along the sensorimotor-association cortical axis. Ketamine consistently increased activation in the dorsomedial prefrontal cortex. The review calls for future adoption of pre-registration, standardized processing and statistical testing, and data sharing to improve rigor.
During wakefulness, people respond to external stimuli, while in dreams or drug-induced dissociated states, vivid internal experiences occur with reduced perception of the outside world. The brain's activity near a critical point between damped and exploding oscillations is linked to conscious experience, and this signature appears in both normal wakefulness and dissociative states but not in dreamless sleep or anesthesia. Using high-density EEG in human male volunteers given escalating ketamine doses, activity became progressively more stable, especially at higher frequencies, as dissociative symptoms increased. This stabilization correlated with reduced ability to perceive external stimuli, not with conscious experience itself. Combining statistical and dynamical measures of criticality may help distinguish wakefulness, dissociation, and unconsciousness.