LSD flattens the hierarchy of directed information flow in fast whole-brain dynamics.
Kenneth Shinozuka, Prejaas K.b. Tewarie, Andrea Luppi, Christopher Lynn, Leor Roseman, Suresh Muthukumaraswamy, David J. Nutt, Robin Carhart-Harris, Gustavo Deco, Morten L. Kringelbach
Imaging Neurosci (Camb) January 3, 2025 DOI: 10.1162/imag_a_00420 via PubMed
Summary
AI-generated from the abstractLSD weakens the brain's usual hierarchy of information flow by making neural communication more balanced between sending and receiving signals. Using magnetoencephalography (MEG) data from 16 healthy adults given 75 micrograms of LSD intravenously, researchers measured directed functional connectivity under four conditions (eyes-closed with or without music, eyes-open with or without video). Across the whole brain, LSD reduced the asymmetry of directed connectivity over time. Machine learning classifiers distinguished LSD from placebo more accurately using hierarchy metrics than traditional connectivity measures. These results indicate that LSD flattens the brain's hierarchical information processing by increasing the balance between senders and receivers of neural signals.
Study at a glance
| Characteristics | Observational cohort Peer reviewed |
|---|---|
| Sample size | 16 |
| Population | Healthy human participants |
| Intervention | LSD |
| Dose | 75 micrograms, intravenous |
| Keywords | LSD Compound Hierarchical system Top-down information flow Usual brain hierarchy Centralized exchange |
| Citations | 9 |
| Key finding | LSD diminishes the asymmetry of directed connectivity across the whole brain, indicating a flattening of the hierarchy of information flow. |
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 properties of 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: eyes-closed with or without music and eyes-open with or without a video stimulus. Across the whole brain, 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.