The flattening of spacetime hierarchy of the N,N-dimethyltryptamine brain state is characterized by harmonic decomposition of spacetime (HADES) framework.
Jakub Vohryzek, Joana Cabral, Christopher Timmermann, Selen Atasoy, Leor Roseman, David J Nutt, Robin L Carhart-Harris, Gustavo Deco, Morten L Kringelbach
National science review May 1, 2024 DOI: 10.1093/nsr/nwae124 via PubMed
Summary
AI-generated from the abstractThe human brain's activity constantly reorganizes across space and time, and decomposing whole-brain recordings into harmonic modes reveals gradient-like patterns linked to different functions. Using the HADES framework, researchers analyzed brain activity in healthy participants after taking the serotonergic psychedelic DMT. They found significant decreases in contributions across most low-frequency harmonic modes during the DMT state. Specifically, the second functional harmonic, which represents the uni- to transmodal functional hierarchy, decreased, supporting the hypothesis that psychedelics alter this hierarchy. Dynamic measures of fractional occupancy, lifetime, and latent space precisely described the changes in the brain's spacetime hierarchical organization during the psychedelic state.
Study at a glance
| Characteristics | Experimental study Peer reviewed |
|---|---|
| Population | Healthy participants |
| Interventions | N N-dimethyltryptamine (DMT) |
| Topics | DMT |
| Keywords | Harmonic modes Spatio-temporal brain dynamics Psychedelics hallucinogens Entheogens |
| Citations | 13 |
| Key finding | DMT decreases contributions across most low-frequency harmonic modes, particularly the second functional harmonic representing the uni- to transmodal functional hierarchy, supporting the hypothesis that psychedelics alter functional hierarchy. |
Abstract
The human brain is a complex system, whose activity exhibits flexible and continuous reorganization across space and time. The decomposition of whole-brain recordings into harmonic modes has revealed a repertoire of gradient-like activity patterns associated with distinct brain functions. However, the way these activity patterns are expressed over time with their changes in various brain states remains unclear. Here, we investigate healthy participants taking the serotonergic psychedelic N,N-dimethyltryptamine (DMT) with the Harmonic Decomposition of Spacetime (HADES) framework that can characterize how different harmonic modes defined in space are expressed over time. HADES demonstrates significant decreases in contributions across most low-frequency harmonic modes in the DMT-induced brain state. When normalizing the contributions by condition (DMT and non-DMT), we detect a decrease specifically in the second functional harmonic, which represents the uni- to transmodal functional hierarchy of the brain, supporting the leading hypothesis that functional hierarchy is changed in psychedelics. Moreover, HADES' dynamic spacetime measures of fractional occupancy, life time and latent space provide a precise description of the significant changes of the spacetime hierarchical organization of brain activity in the psychedelic state.