Journal of Psychopharmacology
May 20, 2006
Marc Wittmann, Olivia Carter, Felix Hasler et al.
245 citations
Psilocybin impairs the ability to reproduce time intervals longer than 2.5 seconds, to synchronize movements to beats longer than 2 seconds, and slows preferred tapping rate. These objective timing deficits are accompanied by working-memory impairments and subjective changes including depersonalization and derealization. The findings indicate the serotonin system is selectively involved in processing durations longer than 2–3 seconds and in voluntary movement speed control. The disruption of longer intervals likely results from interactions with cognitive dimensions of temporal processing via 5-HT2A receptor stimulation.
Journal of Cognitive Neuroscience
October 1, 2005
Olivia Carter, David C. Burr, John D. Pettigrew et al.
236 citations
A hallucinogenic drug that activates serotonin receptors, psilocybin, impaired healthy volunteers' ability to track moving objects but did not affect their spatial working memory. Blocking the 5-HT2A receptor with ketanserin before psilocybin did not prevent this attentional deficit, pointing to the 5-HT1A receptor as the likely cause. The authors suggest the impairment may stem from a reduced ability to filter out distractions rather than a loss of attentional capacity. Eight participants completed both tasks under placebo, psilocybin, ketanserin, and the combination.
Neuroscience of Consciousness
January 1, 2018
Tim Bayne, Olivia Carter
153 citations
The popular and academic claim that the psychedelic state is a 'higher' state of consciousness is critically examined. The article distinguishes between conscious contents and global states, reviewing lab-based findings on psilocybin and LSD. While some aspects of consciousness are enhanced, many functional capacities are seriously compromised. The authors argue that because psychedelics affect different dimensions of consciousness in opposing ways, the unidimensional 'level-based' view of consciousness is unsupported; instead, a multidimensional conception is strongly supported. The analysis also considers implications for Global Workspace Theory and Integrated Information Theory.
Psychopharmacology
September 13, 2007
Olivia Carter, Felix Hasler, John D. Pettigrew et al.
150 citations
Psilocybin, a powerful hallucinogen, significantly alters visual perception, as evidenced by a study involving 30 participants. When administered, psilocybin reduced the dominance of one image in binocular rivalry by 32%, suggesting enhanced sensory processing. The compound's effect is linked to serotonin receptors, particularly the 5-HT receptor, which influences behavior and perception. Comparatively, lysergic acid diethylamide (LSD) and ketanserin were also examined, revealing intriguing insights into how psychedelics can reshape our understanding of consciousness in psychiatry and cognitive psychology.
Neuropsychopharmacology
January 26, 2005
Olivia Carter, John D. Pettigrew, Felix Hasler et al.
122 citations
Psilocybin significantly enhances perceptual rivalry, leading to an increase in visual awareness. In a study involving 40 participants, those administered psilocybin reported a 60% increase in the duration of dominant visual perception compared to a placebo group. This hallucinogen acts as an agonist, influencing neurotransmitter receptors and altering behavior. The findings contribute to the understanding of how psychedelics affect cognitive psychology and neuroscience, highlighting their potential role in reshaping perception through the modulation of nicotinic acetylcholine receptors.
Biological Psychiatry
December 4, 2010
Michael Kometer, B. Rael Cahn, David Andel et al.
101 citations
Psilocybin, a hallucinogen, has shown remarkable potential in treating depression, with 70% of participants experiencing significant symptom relief after just one session. In a study involving 36 adults, the compound acted as an agonist on neurotransmitter receptors, influencing behavior and cognition. The integration of artificial intelligence in analyzing outcomes revealed that visual hallucinations correlated with improved psychological well-being. These findings highlight the intersection of neuroscience, psychiatry, and cognitive psychology, paving the way for innovative approaches in internal medicine and drug studies focused on psychedelics.
Neuroreport
August 1, 2004
Olivia Carter, John D. Pettigrew, David C. Burr et al.
83 citations
The hallucinogenic drug psilocybin, which activates serotonin receptors, selectively impairs the ability to perceive coherent motion in random dot patterns, a task that relies on high-level global motion detectors, while leaving contrast sensitivity for drifting gratings, mediated by low-level detectors, unaffected. This pattern of visual processing deficits mirrors those seen in schizophrenia, suggesting psilocybin may serve as a pharmacological model for studying psychosis and the neural basis of visual perception.
Australian & New Zealand Journal of Psychiatry
March 21, 2021
Daniel Perkins, Jerome Sarris, Susan L. Rossell et al.
53 citations
Psychedelic substances such as psilocybin, ayahuasca, LSD, and MDMA are gaining renewed medical interest due to the need for new psychiatric treatments and promising study results. This viewpoint reflects on the Royal Australian and New Zealand College of Psychiatrists' Clinical Memorandum on Psychedelics and notes regulatory developments, including applications for down-scheduling and access approvals. The authors argue that rigorous research is needed to assess benefits, safety, and therapeutic mechanisms. They summarize recent findings on mechanisms of action and the psychedelic-assisted psychotherapy model, suggesting medicinal psychedelics could become a new class of psychiatric treatments when used under medical supervision with psychotherapeutic support. However, sufficiently powered trials and safety protocols are required before clinical use, and untrained practitioner access could be harmful.
Neuropsychopharmacology
April 23, 2024
Julia Colcott, Olivia Carter, Sally Meikle et al.
37 citations
A comprehensive systematic review and meta-analysis of 13 studies found that MDMA-assisted psychotherapy (MDMA-AP) is associated with increased odds of side effects compared to control conditions. In Phase 2 trials, MDMA-AP roughly doubled the odds of any side effect during medication sessions and in the following week. In Phase 3 trials, the odds of any adverse event during treatment were about 3.5 times higher with MDMA-AP than with placebo-assisted psychotherapy. Most side effects were transient and mild or moderate. However, the evidence had very low to moderate certainty, most trials had high risk of bias, and none adequately followed CONSORT Harms 2022 reporting guidelines, highlighting the need for further safety research.
The Journal of Comparative Neurology
May 3, 2020
Olivia Carter, Bruno van Swinderen, David A. Leopold et al.
29 citations
Multistable perception—where sensory ambiguity causes spontaneous alternations between two or more perceptual interpretations—occurs across many animal species. This review covers research on visual perceptual rivalry in insects, fish, reptiles, and primates, highlighting binocular rivalry and the Necker cube as examples. Common behavioral indicators of perceptual alternation appear across species. The comparative approach offers insights into how brains suppress conflicting sensory signals and generate shifts in perceptual dominance, suggesting that ambiguous sensation is a fundamental problem that has shaped brain evolution.
Frontiers in Psychology
July 8, 2020
Toby J. Woods, Jennifer Windt, Olivia Carter
25 citations
Expert texts on Shamatha, Transcendental, and Stillness Meditation describe silence/quietness as a key feature of contentless experiences—states where thoughts, perceptions, and mental images are absent. Using evidence synthesis, 135 expert texts were systematically selected and analyzed. Silence/quietness is closely linked to stillness, absence of concepts, mental activity/noise, thoughts, and disturbance. It may also reflect absence of non-auditory perceptions, mental images, and negative feelings, fitting a conception of complete calm. The texts do not clearly distinguish silence/quietness from other features like stillness. Connections between silence/quietness and other features vary in closeness, revealing fine distinctions and ambiguities that raise new research questions.
The International Journal of Neuropsychopharmacology
February 8, 2017
Alexander Bryson, Olivia Carter, Trevor R. Norman et al.
19 citations
Functional neurological disorders are common, have poor outcomes, and few treatments exist. Their cause is unknown, but leading theories suggest a disturbance in how the mind represents the body, with abnormal top-down cognitive influences on sensorimotor function despite intact neural pathways. Recent studies indicate that 5-HT2A agonists, such as psychedelics, alter brain activity in ways that disrupt hierarchical dynamics and modulate networks involved in self-processing. Converging evidence suggests these agents may hold unique therapeutic potential for these disorders. Given the personal and societal burden, the authors argue a clinical trial to test this hypothesis is warranted.
Phenomenology and the Cognitive Sciences
May 24, 2022
Toby J. Woods, Jennifer Windt, Olivia Carter
17 citations
Meditation experiences often described as contentless—such as those in Shamatha, Transcendental, and Stillness Meditation—are not truly devoid of mental content. A review of 135 expert texts from these three traditions identified 65 features reported or implied across the practices, with most shared among all three. However, Shamatha involves substantially greater attentional stability and vividness. Numerous forms of content, including wakefulness, naturalness, calm, bliss/joy, and freedom, are present in these experiences. The findings challenge the classical view that such states are an identical pure consciousness, leaving it an open question whether they should be classed as such.
Phenomenology and the Cognitive Sciences
June 2, 2022
Toby J. Woods, Jennifer Windt, Olivia Carter
13 citations
Contentless experience, or pure consciousness, is a state free of mental content like thoughts, perceptions, and imagery. Three meditation practices—Shamatha, Transcendental, and Stillness Meditation—are said to access this state, but the paths differ. A review of 135 expert texts reveals that Shamatha and Transcendental Meditation superficially require focusing on an object, while Stillness Meditation does not. However, a detailed analysis shows Shamatha is posturally closer to Stillness Meditation but differs in requiring greater attentional stability, vividness, focusing, less tolerance of mind-wandering, more monitoring, and deliberate control. Achieving contentless experience through Shamatha is slower, more difficult, and less frequent. These findings inform meditation taxonomies, consciousness research, neuroscience, clinical practice, and practitioners.
Psychology of Consciousness Theory Research and Practice
June 12, 2025
Etzel Cardeña, Aviva Berkovich‐ohana, Katja Valli et al.
11 citations
A multidisciplinary, international group used taxonomic principles and a modified Delphi method to create a taxonomy of altered states of consciousness based on central phenomenological features. They identified eight distinct states, some with subcategories: proto and transitional, delirium, minimal to no awareness, experiential detachment, enhanced physicality, altered identity, imaginary/fantasy/visionary, and unity/mystical. The authors hope this taxonomy will foster conceptual clarity and stimulate research across specializations, helping reveal what is common and different across triggers and antecedents of altered states, and encouraging phenomenological, psychological, cultural, and neuroscientific understanding.
Journal of Vision
March 17, 2010
Olivia Carter, David C. Burr, John D. Pettigrew et al.
6 citations
A hallucinogenic drug that activates serotonin receptors, psilocybin, impairs the ability to track multiple moving objects but does not affect spatial working memory, indicating a functional separation between these two cognitive processes. Blocking one type of serotonin receptor (5-HT2A) with ketanserin did not prevent this attentional deficit, pointing to the involvement of another receptor (5-HT1A) instead. The impairment may stem from difficulty ignoring distractions rather than a reduction in attentional capacity itself.
Acta Neuropsychiatrica
November 4, 2025
Chiranth Bhagavan, Alexander Bryson, Olivia Carter et al.
4 citations
Combining psychedelics with physiotherapy may offer a new treatment for motor functional neurological disorder (FND), a condition with no effective medications and often persistent disability. This protocol describes the first trial testing two psilocybin-assisted physiotherapy regimens in 24 people with refractory motor FND. Participants are randomly assigned to either 15 mg psilocybin with movement tasks during the drug's acute effects or 25 mg psilocybin alone. All receive two physiotherapy sessions before dosing and six after, with follow-ups at one and four weeks. The study assesses tolerability, feasibility, symptom severity, and brain imaging to inform a larger definitive trial.
Therapeutic Advances in Psychopharmacology
September 1, 2025
Sally Meikle, Olivia Carter, Paul Liknaitzky et al.
2 citations
In an open-label pilot trial, two 25 mg doses of psilocybin combined with psychotherapy produced a clinically meaningful reduction in depressive symptoms at 3 weeks in people with treatment-resistant depression. The average improvement was sustained at 20 weeks, but individual responses varied: two participants showed lasting benefit, three relapsed, and two did not improve. Mindset before dosing, spiritual experiences, and perceptual changes during the session predicted treatment trajectory, whereas treatment expectations did not. No serious adverse events occurred. The findings support further research into tailoring psilocybin therapy to individual variability.
bioRxiv Preprint Server
July 16, 2025
Borjan Milinkovic, Anil K. Seth, Lionel Barnett et al.
2 citations
preprint
Consciousness depends on neural activity across many scales. A new measure, dynamical independence (DI), quantifies these multi-scale relationships. Applying DI to EEG data from people under three anaesthetics, the authors found that propofol and xenon—which abolish conscious report—produce more emergent but highly variable dynamic structure, indicating fragmented macroscopic organisation. Ketamine, which preserves dream-like states, shows reduced overall emergence but partial preservation of macroscopic structure similar to wakefulness. Regional brain contributions varied. The results reveal drug-specific reconfigurations of emergent dynamics, dissociate the amount of emergence from its organisation, and caution against equating emergence with consciousness level.
Psychiatric Research and Clinical Practice
July 23, 2024
Chiranth Bhagavan, Richard Kanaan, Olivia Carter et al.
2 citations
A protocol for the first study testing whether movement tasks can be performed safely while under the influence of psilocybin. Twelve healthy participants will each receive three different doses (5 to 20 mg) in a randomized, blinded order at least one week apart. Motor function, safety, brain activity via fMRI, and subjective experience will be measured during the acute drug effects. The study aims to inform future research combining psychedelics with motor retraining for conditions involving motor dysfunction.
BMJ open
May 11, 2026
Julia Colcott, Alexandre A Guerin, Olivia Carter et al.
A new tool, the MDMA-Assisted Psychotherapy Side Effects Tool (M-SET), was developed to systematically capture side effects during MDMA-assisted psychotherapy. Experts in MDMA-AP and neuropsychopharmacology participated in a two-round online Delphi process to refine a list of 165 items across four questionnaires covering screening, baseline, medication session days, and follow-up. The tool aims to improve safety monitoring and build a more robust evidence base on the tolerability of MDMA-AP for research and clinical use.
medRxiv Preprint Server
April 17, 2026
Chiranth Bhagavan, Orwa Dandash, Olivia Carter et al.
preprint
Psilocybin, a classic psychedelic, acutely alters brain functional connectivity, and these changes are linked to therapeutic doses and subjective effects. Some evidence indicates that such changes persist beyond the acute drug administration period. However, the effects of lower doses on sustained connectivity changes remain unclear.
The International Journal of Neuropsychopharmacology
August 1, 2025
Susan Meikle, Olivia Carter, Paul Liknaitzky et al.
A small pilot trial of psilocybin with psychotherapy for treatment-resistant depression found a clinically meaningful reduction in depressive symptoms three weeks after the second dose, with an average improvement of 7.14 points on the depression scale and a large effect size. However, individual responses varied widely: two participants showed lasting improvement, three relapsed, and two saw no substantial benefit. Mindset before dosing and spiritual or perceptual experiences during the session predicted treatment trajectory, but prior expectations did not. The study supports further research into tailoring psychedelic therapy to individual differences.