Neuroimaging & Brain MeasuresHealthy VolunteersLSD

LSD alters dynamic integration and segregation in the human brain

This fMRI study (2020) improves our understanding of how LSD changes brain function over time and how subjective effects (e.g. ego dissolution) map onto these changes.

Authors

  • Robin Carhart-Harris
  • Leor Roseman
  • Andrea Luppi

Published

NeuroImage
individual Study

Abstract

Investigating changes in brain function induced by mind-altering substances such as LSD is a powerful method for interrogating and understanding how mind interfaces with brain, by connecting novel psychological phenomena with their neurobiological correlates. LSD is known to increase measures of brain complexity, potentially reflecting a neurobiological correlate of the especially rich phenomenological content of psychedelic-induced experiences. Yet although the subjective stream of consciousness is a constant ebb and flow, no studies to date have investigated how LSD influences the dynamics of functional connectivity in the human brain. Focusing on the two fundamental network properties of integration and segregation, here we combined graph theory and dynamic functional connectivity from resting-state functional MRI to examine time-resolved effects of LSD on brain networks properties and subjective experiences. Our main finding is that the effects of LSD on brain function and subjective experience are non-uniform in time: LSD makes globally segregated sub-states of dynamic functional connectivity more complex, and weakens the relationship between functional and anatomical connectivity. On a regional level, LSD reduces functional connectivity of the anterior medial prefrontal cortex, specifically during states of high segregation. Time-specific effects were correlated with different aspects of subjective experiences; in particular, ego dissolution was predicted by increased small-world organisation during a state of high global integration. These results reveal a more nuanced, temporally-specific picture of altered brain connectivity and complexity under psychedelics than has previously been reported.

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Research Summary of 'LSD alters dynamic integration and segregation in the human brain'

Introduction

Luppi and colleagues situate their study within recent efforts to link psychedelic-induced alterations of consciousness to their neurobiological substrates using non-invasive imaging. Prior work indicates that serotonergic psychedelics such as LSD, psilocybin and DMT increase measures of brain complexity and alter functional connectivity, typically reducing within-network integrity while increasing between-network coupling. The authors note that the stream of consciousness is inherently dynamic, and that previous studies have largely neglected temporal fluctuations in functional connectivity. They argue that integration and segregation are fundamental network properties relevant to consciousness and hypothesise that LSD's effects may be temporally specific rather than uniform across time. This study therefore aimed to combine graph theory with dynamic functional connectivity (dFC) from resting-state fMRI to test whether LSD alters time-resolved network organisation, focusing on integrated versus segregated dynamic sub-states. Following the Entropic/Anarchic Brain framework, the researchers predicted that LSD would produce effects broadly opposite to those observed during loss of consciousness, and that these effects would be differentially expressed during integrated and segregated dFC sub-states. The investigation used a placebo-controlled design in healthy volunteers with prior psychedelic experience to examine network-level and regional changes and their relation to subjective experience.

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Study Details

References (26)

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