Journal of psychopharmacology (Oxford, England)
June 18, 2025
Maria Bălăeţ, William Trender, Annalaura Lerede et al.
2 citations
Mental health implications of COVID-19 drug use patterns are still unclear. We used data-driven clustering in a large citizen science cohort recruited agnostically to an interest in drug-use to categorise people according to common patterns of drug use and analysed their mental health symptoms (GAD-7 and PHQ-9 items), from recruitment prior to COVID-19 restrictions in 2020 (N = 242,260) to...
UNC Libraries
April 22, 2020
Peter J. Hellyer, Luke T. J. Williams, Ben Sessa et al.
1 citation
Lysergic acid diethylamide (LSD), the prototypical “psychedelic,” may be unique among psychoactive substances. In the decades that followed its discovery, the magnitude of its effect on science, the arts, and society was unprecedented. LSD produces profound, sometimes life-changing experiences in microgram doses, making it a particularly powerful scientific tool. Here we sought to examine its...
Neuroscience and Biobehavioral Reviews
April 1, 2019
Federico Turkheimer, Peter J. Hellyer, Angie A. Kehagia et al.
The concept of "emergence" has become commonplace in the modelling of complex systems, both natural and man-made; a functional property" emerges" from a system when it cannot be readily explained by the properties of the system's sub-units. A bewildering array of adaptive and sophisticated behaviours can be observed from large ensembles of elementary agents such as ant colonies, bird flocks or...
PLoS Computational Biology
August 24, 2017
Peter J. Hellyer, Claudia Clopath, Angie A. Kehagia et al.
21 citations
In recent years, there have been many computational simulations of spontaneous neural dynamics. Here, we describe a simple model of spontaneous neural dynamics that controls an agent moving in a simple virtual environment. These dynamics generate interesting brain-environment feedback interactions that rapidly destabilize neural and behavioral dynamics demonstrating the need for homeostatic...
Proc Natl Acad Sci U S A
April 11, 2016
Robin Carhart-Harris, Suresh Muthukumaraswamy, Leor Roseman et al.
887 citations
Lysergic acid diethylamide (LSD) is the prototypical psychedelic drug, but its effects on the human brain have never been studied before with modern neuroimaging. Here, three complementary neuroimaging techniques: arterial spin labeling (ASL), blood oxygen level-dependent (BOLD) measures, and magnetoencephalography (MEG), implemented during resting state conditions, revealed marked changes in...
Journal of The Royal Society Interface
October 29, 2014
Giovanni Petri, Paul Expert, Federico Turkheimer et al.
689 citations
Networks, as efficient representations of complex systems, have appealed to scientists for a long time and now permeate many areas of science, including neuroimaging (Bullmore and Sporns 2009 Nat. Rev. Neurosci. 10 , 186–198. ( doi:10.1038/nrn2618 )). Traditionally, the structure of complex networks has been studied through their statistical properties and metrics concerned with node and link...
Journal of Neuroscience
January 8, 2014
Peter J. Hellyer, Murray Shanahan, Gregory Scott et al.
225 citations
Understanding how dynamic changes in brain activity control behavior is a major challenge of cognitive neuroscience. Here, we consider the brain as a complex dynamic system and define two measures of brain dynamics: the synchrony of brain activity, measured by the spatial coherence of the BOLD signal across regions of the brain; and metastability, which we define as the extent to which...
Frontiers in Human Neuroscience
2014
Robin Carhart-Harris, Robert Leech, Peter J. Hellyer et al.
1,289 citations
Entropy is a dimensionless quantity that is used for measuring uncertainty about the state of a system but it can also imply physical qualities, where high entropy is synonymous with high disorder. Entropy is applied here in the context of states of consciousness and their associated neurodynamics, with a particular focus on the psychedelic state. The psychedelic state is considered an exemplar...