LSD flattens the hierarchy of directed information flow in fast whole-brain dynamics
OpenAlex – April 28, 2024
Source: OpenAlex
Summary
Psychedelics profoundly reshape consciousness by flattening the brain's information flow hierarchy. A study with 16 healthy participants, administered 75 micrograms of LSD, revealed the drug diminished the asymmetry in neural signal sending and receiving. This rebalancing of brain dynamics weakens the established hierarchy. Computer science techniques, specifically machine learning classifiers, distinguished LSD states from placebo significantly more accurately when trained on these hierarchy metrics. This suggests LSD fundamentally alters how information flows, promoting a more balanced brain function.
Abstract
Abstract Psychedelics are serotonergic drugs that profoundly alter consciousness, yet their neural mechanisms are not fully understood. A popular theory, RElaxed Beliefs Under pSychedelics (REBUS), posits that psychedelics flatten the hierarchy of information flow in the brain. Here, we investigate hierarchy based on the imbalance between sending and receiving brain signals, as determined by directed functional connectivity. We measure directed functional hierarchy in a magnetoencephalography (MEG) dataset of 16 healthy human participants who were administered a psychedelic dose (75 micrograms, intravenous) of lysergic acid diethylamide (LSD) under four different conditions. LSD diminishes the asymmetry of directed connectivity when averaged across time. Additionally, we demonstrate that machine learning classifiers distinguish between LSD and placebo more accurately when trained on one of our hierarchy metrics than when trained on traditional measures of functional connectivity. Taken together, these results indicate that LSD weakens the hierarchy of directed connectivity in the brain by increasing the balance between senders and receivers of neural signals.