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Leor Roseman

University of Exeter, Phillips Exeter Academy

132 papers in the library · 11,490 citations · publishing 2014-2026

Papers

Diminished functional gradient of the precuneus during altered states of consciousness

bioRxiv December 17, 2024 Dian Lyu, Ram Adapa, Robin L. Carhart-Harris et al. preprint

The default mode network (DMN) and frontoparietal control network (FPCN), typically anticorrelated at rest in healthy brains, show continuous rather than absolute anatomical boundaries in the posterior precuneus. Connectivity differences along the dorsal-ventral axis follow linear slopes, forming functional gradients that exist only within each network's territory. These gradients flatten in altered states of consciousness (ASC), with the gradient magnitude similarly impaired across different ASC types, while spatial entropy differs between psychedelic and sedative states. The findings suggest the DMN and FPCN, though appearing distinct, may originate from a single integrated mechanism, and the loss of functional differentiation between them characterizes altered conscious states.

Human brain changes after first psilocybin use

October 14, 2024 Terence J. Lyons, Merle Spriggs, Leevi Kerkelä et al. preprint

A single high dose of psilocybin (25 mg) produced lasting functional and anatomical brain changes in healthy, psychedelic-naive adults, detected from one hour to one month later. Diffusion imaging showed decreased axial diffusivity in prefrontal-subcortical tracts, correlating with reduced brain network modularity, which in turn correlated with improved well-being. Increased cortical signal entropy shortly after dosing predicted better psychological well-being at one month, with next-day psychological insight mediating this relationship. No such effects occurred with a 1 mg placebo dose. Cognitive flexibility, psychological insight, and well-being also increased at one month.

Reply to Letter to the Editor: "Psychedelics in Older Adults: Difficulties of a Clear Therapeutic Evidence".

Am J Geriatr Psychiatry September 26, 2024 Hannes Kettner, Leor Roseman, Adam Gazzaley et al.

A reply to a letter to the editor addresses difficulties in establishing clear therapeutic evidence for psychedelics in older adults. The response likely discusses challenges such as study design, sample size, and confounding factors that complicate the interpretation of clinical data on psychedelic treatments for this population. It emphasizes the need for rigorous research to clarify the potential benefits and risks of psychedelic therapy in geriatric mental health care.

The intimacy of psychedelics, language, and consciousness.

May 2, 2024 Jeremy I Skipper, George Fejer, Matthieu Koroma et al. preprint

Language plays a generative role in shaping and sustaining consciousness, not merely reporting it. Cognitive neuroscientist Jeremy I. Skipper argues against localizationist models of language processing, emphasizing context-dependent and dynamic brain recruitment. Aphasic patients report loss of self-narrative and increased connectedness, paralleling psychedelic states where linguistic categories dissolve and ineffability arises. Potential neural mechanisms linking language disruption to psychedelic experiences are outlined. The UNITy Project aims to study post-acute meaning-making processes and predict changes in language and well-being after psychedelic sessions.

Observational cohort study of a group-based VR program to improve mental health and wellbeing in people with life-threatening illnesses

Joe Hardy, Hannes Kettner, David Glowacki et al. preprint

A group-based virtual reality program called Clear Light, delivered at home over three weeks, improved anxiety, depression, and wellbeing in people with life-threatening illnesses. The program included multi-user VR experiences, video calls, and text chats designed to elicit self-transcendent experiences similar to psychedelics. In a small observational study of 15 participants, moderate improvements were seen in anxiety, depression, wellbeing, demoralization, connectedness, and spiritual wellbeing. The intervention was well-tolerated. The findings suggest potential benefits but are limited by the lack of a comparison group, indicating the need for randomized controlled trials.

Ceremonial Psychedelic Experiences and Changes in Mental Health Outcomes in Those with Adverse Childhood Experiences

Psychedelic Medicine December 15, 2025 M. Mehmood, Rebecka Bremler, M. Spriggs et al.

People who experienced more adverse childhood experiences (ACEs) showed greater improvements in mental well-being, reductions in experiential avoidance, and lower trait anxiety after participating in psychedelic ceremonies compared to those with fewer ACEs. Higher ACE scores were also linked to stronger emotional breakthrough and mystical experiences during the psychedelic session. Among individuals with four or more ACEs, those who reported stronger mystical or emotional breakthrough experiences had better well-being at two and four weeks afterward, and mystical experiences were linked to less experiential avoidance while emotional breakthrough was linked to less anxiety at four weeks. However, the acute experiences did not significantly change how ACEs affected mental health outcomes overall.

How to set up a psychedelic study: Unique considerations for research involving human participants

arXiv Preprint Archive March 28, 2025 Marcus J. Glennon, Catherine I. V. 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.