Frontiers in Human Neuroscience
May 27, 2014
Leor Roseman, Robert Leech, Amanda Feilding et al.
293 citations
Perturbing a system and observing the consequences is a classic scientific strategy for understanding a phenomenon. Psychedelic drugs perturb consciousness in a marked and novel way and thus are powerful tools for studying its mechanisms. In the present analysis, we measured changes in resting-state functional connectivity (RSFC) between a standard template of different independent components...
arXiv Preprint Archive
May 26, 2014
Enzo Tagliazucchi, Robin Carhart-Harris, Robert Leech et al.
The study of rapid changes in brain dynamics and functional connectivity (FC) is of increasing interest in neuroimaging. Brain states departing from normal waking consciousness are expected to be accompanied by alterations in the aforementioned dynamics. In particular, the psychedelic experience produced by psilocybin (a substance found in `magic mushrooms`) is characterized by unconstrained...
Biological Psychiatry
January 10, 2014
Robin Carhart-Harris, Kevin Murphy, Robert Leech et al.
182 citations
The MTLs appear to be specifically implicated in the mechanism of action of MDMA, but further work is required to elucidate how the drug's characteristic subjective effects arise from its modulation of spontaneous brain activity.
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...
Schizophrenia Bulletin
October 6, 2012
Robin Carhart-Harris, Robert Leech, David Erritzøe et al.
267 citations
Psilocybin is a classic psychedelic and a candidate drug model of psychosis. This study measured the effects of psilocybin on resting-state network and thalamocortical functional connectivity (FC) using functional magnetic resonance imaging (fMRI). Fifteen healthy volunteers received intravenous infusions of psilocybin and placebo in 2 task-free resting-state scans. Primary analyses focused on...
The British Journal of Psychiatry
January 27, 2012
Robin Carhart-Harris, Robert Leech, Tom A. Williams et al.
241 citations
Background Psilocybin is a classic psychedelic drug that has a history of use in psychotherapy. One of the rationales for its use was that it aids emotional insight by lowering psychological defences. Aims To test the hypothesis that psilocybin facilitates access to personal memories and emotions by comparing subjective and neural responses to positive autobiographical memories under psilocybin...
Proceedings of the National Academy of Sciences
January 23, 2012
Alessandro Colasanti, Robin J. Tyacke, Robert Leech et al.
1,191 citations
Psychedelic drugs have a long history of use in healing ceremonies, but despite renewed interest in their therapeutic potential, we continue to know very little about how they work in the brain. Here we used psilocybin, a classic psychedelic found in magic mushrooms, and a task-free functional MRI (fMRI) protocol designed to capture the transition from normal waking consciousness to the...
Journal of Neuroscience
March 2, 2011
Robert Leech, Salwa Kamourieh, Christian Beckmann et al.
801 citations
The posterior cingulate cortex (PCC) is a central part of the default mode network (DMN) and part of the structural core of the brain. Although the PCC often shows consistent deactivation when attention is focused on external events, anatomical studies show that the region is not homogeneous, and electrophysiological recordings in nonhuman primates suggest that it is directly involved in some...