Harmonic decomposition of spacetime (HADES) framework characterises the spacetime hierarchy of the DMT brain state
Jakub Vohryzek, Joana Cabral, Christopher Timmermann, Selen Atasoy, Leor Roseman, David Nutt, Robin Carhart-Harris, Gustavo Deco, Morten L. Kringelbach
bioRxiv August 21, 2023 preprint DOI: 10.1101/2023.08.20.554019 (opens in new tab)
Study at a glance
AI-extracted from the abstract| Characteristics | Proof-of-principle study |
|---|---|
| Population | Healthy participants |
| Interventions | N N-Dimethyltryptamine (DMT) |
| Topics | DMT |
| Keywords | Psychedelics Hallucinogens Psychoactive drugs Brain science Neurobiology Cognitive science Neural research Brain activity Neural activity Brain function Information processing Brain dynamics Cognitive processing Spacetime hierarchy Brain organization Neural architecture Spatiotemporal organization Cortical structure Brain networks |
| Citations | 7 |
| Key points | DMT significantly decreases contributions from most low-frequency harmonic modes and specifically reduces the second functional harmonic representing the uni- to transmodal functional hierarchy, supporting the hypothesis that psychedelics alter brain functional hierarchy. |
Abstract
Abstract The human brain is a complex system, whose activity exhibits flexible and continuous reorganisation 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. In this study, we develop the Harmonic Decomposition of Spacetime (HADES) framework that characterises how different harmonic modes defined in space are expressed over time , and, as a proof-of-principle, demonstrate the sensitivity and robustness of this approach to specific changes induced by the serotonergic psychedelic N,N-Dimethyltryptamine (DMT) in healthy participants. 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 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.