Journal of Vision
September 1, 2016
Leor Roseman, Martin I. Sereno, Robert Leech et al.
4 citations
Under LSD, the visual cortex's resting-state functional connectivity (RSFC) becomes more dependent on its intrinsic retinotopic organization, as if the brain were processing actual visual input despite closed eyes. In 10 healthy subjects, RSFC between non-adjacent patches of V1 and V3 that represent congruent parts of the visual field (both horizontal or both vertical meridians) was significantly stronger than connectivity between incongruent patches (horizontal-vertical), compared to placebo. The difference between congruent and incongruent connectivity was greater under LSD (Cohen's d=1.6), suggesting that psychedelic imagery involves transient local retinotopic activation similar to that from visual stimulation.
Neuroscience and Biobehavioral Reviews
July 1, 2026
Marcus J. Glennon, Catherine Bird, Prateek Yadav et al.
2 citations
Setting up a psychedelic research study involves a long, arduous, and Kafkaesque process with many unstandardised challenges. These complexities challenge existing assumptions about psychiatric prescribing, the placebo effect, and definitions of selfhood. This review brings together major UK psychedelic research teams to formalise these unique considerations, addressing sociocultural, political, legal, pharmacological, safety, study design, and experiential facets. It identifies continuing areas of debate and provides a practical, experience-based guide with recommendations for policymakers and future researchers intending to set up a psychedelic study or clinical trial.
UNC Libraries
April 22, 2020
Peter J. Hellyer, Luke T. J. Williams, Ben Sessa et al.
1 citation
Lysergic acid diethylamide (LSD) in microgram doses produces profound, sometimes life-changing experiences and is a uniquely powerful psychoactive substance. In the first modern neuroimaging study of LSD, marked changes in brain blood flow, electrical activity, and network communication patterns were observed. These changes correlated strongly with the drug's hallucinatory and consciousness-altering properties. The findings have implications for understanding the neurobiology of consciousness and for potential applications of LSD in psychological research.
Proceedings of the National Academy of Sciences of the United States of America
April 14, 2026
Meichao Zhang, Casey Paquola, Katya Krieger-Redwood et al.
The brain's default mode network (DMN) contains spatially distinct subregions that support different cognitive processes: some DMN areas are more active during perceptual decisions about faces, while others are more active during memory-guided decisions based on previously seen images. These subregions differ in their connectivity profiles—perception-related areas have receiver-like, afferent-biased connections across the heteromodal cortex, whereas memory-related areas have sender-like, efferent-biased connections with perceptual-motor and attentional systems beyond the DMN. This double dissociation, found across three fMRI datasets, suggests that DMN architecture is organized to flexibly support both external perception and internal memory-guided thought.
arXiv Preprint Archive
March 28, 2025
Marcus J. Glennon, Catherine Bird, Prateek Yadav et al.
Setting up a psychedelic study is a long and complex process that presents unique challenges not yet standardized. This review brings together major UK research teams to formalize these considerations, identify ongoing debates, and provide a practical guide for researchers and policymakers. It addresses challenges to existing assumptions about psychiatric prescribing, the placebo effect, and definitions of selfhood. The paper can be read end-to-end or used as a manual with sections for specific needs.
arXiv Preprint Archive
February 4, 2021
Erik D. Fagerholm, Robert Leech, Steven C. R. Williams et al.
Ketamine rapidly reduces depressive symptoms in treatment-resistant major depressive disorder. Using brain imaging and dynamic causal modeling, researchers analyzed neural excitation/inhibition interactions in the primary somatosensory cortex of 18 unmedicated patients and 18 healthy controls during a somatosensory task. Patients were scanned at baseline, 6-9 hours after ketamine infusion, and 6-9 hours after placebo. A shift in neural dynamics toward a stable region of the Poincaré diagram—requiring increased excitatory and inhibitory coupling—predicted symptom improvement specifically after ketamine, not placebo. This drug-specific neural shift may serve as a biomarker for treatment response.
Neuroscience and Biobehavioral Reviews
April 1, 2019
Federico Turkheimer, Peter J. Hellyer, Angie A. Kehagia et al.
Emergence describes how complex systems exhibit properties not easily explained by their individual parts, seen in ant colonies, bird flocks, or brain function. This paper clarifies the concept, distinguishing strong emergence (where properties are irreducible to lower-level mechanisms) from weak emergence (where properties arise from but are explainable by lower-level interactions). It argues that models based on strong emergence, such as the free energy principle and integrated information theory, risk metaphysical implausibility and overdetermination, making them only one of many possible explanations. In contrast, weakly emergent computational models like oscillatory networks, which start from biologically plausible elementary units, are ontologically sound and offer a powerful approach for future neuroscientific research.
arXiv Preprint Archive
May 26, 2014
Enzo Tagliazucchi, Robin Carhart-Harris, Robert Leech et al.
Psilocybin, the active compound in magic mushrooms, dramatically expands the brain's repertoire of connectivity states, revealing how consciousness can be altered. Using advanced brain imaging, researchers tracked neural activity before and after psilocybin administration. Results showed increased signal variability in memory and emotion-processing regions, while higher brain networks displayed enhanced flexibility in their communication patterns.