LSD weakens the brain's directed connectivity hierarchy by increasing the balance between senders and receivers of neural signals. This finding supports the REBUS theory, which proposes that psychedelics flatten the hierarchy of information flow in the brain. Analyzing magnetoencephalography data from 16 healthy participants given 75 micrograms of intravenous LSD, the study found that LSD diminishes the asymmetry of directed connectivity averaged over time. Machine learning classifiers distinguished LSD from placebo more accurately when trained on hierarchy metrics than on traditional functional connectivity measures.
Advanced meditators from the Isha Yoga tradition report stronger non-dual experiences—where the boundary between self and environment dissolves—during breath-watching meditation compared to novices and meditation-naïve controls. Using EEG-based intrinsic neural timescales (INT), researchers found that across all participants, INTs are longer during internal attention (breath-watching) than during an external cognitive task. However, advanced meditators show similar INT durations between internal and external attention, and this reduced difference correlates with stronger reported non-dual experiences. The findings suggest that similar intrinsic neural timescale durations across internal and external attention may be a neural signature of non-duality.