Connectome-harmonic decomposition of human brain activity reveals dynamical repertoire re-organization under LSD

Selen Atasoy,Robin L Carhart-Harris,Morten L Kringelbach,Leor Roseman,Gustavo Deco,Mendel Kaelen

doi:10.1038/s41598-017-17546-0

Abstract

Recent studies have started to elucidate the effects of lysergic acid diethylamide (LSD) on the human brain but the underlying dynamics are not yet fully understood. Here we used ’connectome-harmonic decomposition’, a novel method to investigate the dynamical changes in brain states. We found that LSD alters the energy and the power of individual harmonic brain states in a frequency-selective manner. Remarkably, this leads to an expansion of the repertoire of active brain states, suggestive of a general re-organization of brain dynamics given the non-random increase in co-activation across frequencies. Interestingly, the frequency distribution of the active repertoire of brain states under LSD closely follows power-laws indicating a re-organization of the dynamics at the edge of criticality. Beyond the present findings, these methods open up for a better understanding of the complex brain dynamics in health and disease.

Highlights

The psychoactive effects of lysergic acid diethylamide (LSD) were discovered in 1943 and began to be fully reported on in the late 1940s1 and early 1950s2
We further investigate whether the changes in the activation of individual harmonics lead to any variations in the dynamical repertoire of these harmonics brain states
Exploring the combined effects of music and the psychedelic state induced by LSD provided us an opportunity to reveal the LSD-induced dynamical changes in the brain and how these dynamics are affected by the presence of a complex, natural stimuli like music

Summary

Introduction

The psychoactive effects of lysergic acid diethylamide (LSD) were discovered in 1943 and began to be fully reported on in the late 1940s1 and early 1950s2. The utilization of connectome harmonics as brain states composing complex cortical dynamics offers two important advantages; firstly, the connectome harmonics, by definition, are the spatial extension of the Fourier basis to the particular structural connectivity of the human brain, the human connectome[15] (Fig. 1a–f, Fig. S1), enabling for the first time a spatial harmonic analysis tailored to the human connectome They correspond to spatial cortical patterns formed by fully synchronized neural activity, each associated with a different temporal frequency as well as a different spatial wavelength, as exemplified in the general phenomenon of standing waves and in cymatic patterns[15]. We test whether LSD caused any re-organization of brain dynamics at the edge of criticality-i.e. balance between two extreme tendencies; a quiescent order and a chaotic disorder - as hypothesized by previous theoretical studies of this psychedelic state[11]

Methods

Results

Conclusion