Classic serotonergic psychedelics strongly alter conscious awareness, but how they change the temporal structure of brain activity has been unclear. In a double-blind, placebo-controlled study with 25 participants using high-density EEG, an ayahuasca-inspired formulation (intranasal N,N-DMT and buccal harmine) accelerated neural dynamics: microstate duration decreased and state transitions became more frequent. Surprisingly, the sequence of microstates became less random, showing higher first-order Markov structure. This restructuring involved reduced transitions into one state (M2) and increased prevalence and accessibility of two others (M3 and M5). The psychedelic state thus produces a syntactically reconfigured, highly metastable neural dynamic, not mere randomization.
A formulation combining N,N-Dimethyltryptamine and harmine alters the sequences of metastable EEG topography patterns in the cortex, indicating changes in brain activity dynamics.
Hypnosis alters information processing in the brain's frontoparietal regions, particularly by reducing interhemispheric connectivity and the efficiency of information passing through individual cortical nodes. In a study of 30 hypnosis experts, high-density EEG was recorded during two hypnotic states of different depth—Somnambulism (light) and Esdaile (deep)—and two well-matched control states. Interhemispheric frontoparietal connectivity distinguished hypnosis from control conditions, but no difference was found between the two hypnotic states. Theta power was enhanced during hypnosis. The findings support the idea that altered top-down control in frontoparietal regions facilitates hypnosis by integrating information between cortical hemispheres.
During sleep, the human brain continues to process unexpected sounds, but the neural code becomes delayed, more redundant, and less rich as consciousness wanes. Twenty-nine participants heard an oddball sequence of tones while awake and during an 8-hour sleep opportunity. Prediction error responses occurred in all sleep stages (N1, N2, N3, REM). Mutual information analysis showed a substantial reduction in encoded prediction error information, especially during N3 and REM, even though electrical brain responses (ERPs) grew larger in deeper NREM sleep. Co-information analysis revealed that neural dynamics became increasingly redundant with deeper sleep. The neural code differed between wakefulness and sleep but was largely shared between N2 and N3 stages.