Imperial College London

Dr Samuel Turton

Faculty of MedicineDepartment of Brain Sciences

Honorary Research Associate
 
 
 
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s.turton

 
 
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Burlington DanesHammersmith Campus

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Summary

 

Publications

Publication Type
Year
to

18 results found

Ashok AH, Myers J, Frost G, Turton S, Gunn RN, Passchier J, Colasanti A, Marques TR, Nutt D, Lingford-Hughes A, Howes OD, Rabiner EAet al., 2021, Acute acetate administration increases endogenous opioid levels in the human brain: A [C-11]carfentanil molecular imaging study, JOURNAL OF PSYCHOPHARMACOLOGY, Vol: 35, Pages: 606-610, ISSN: 0269-8811

Journal article

Turton S, Lingford-Hughes A, 2020, Neurobiology and principles of addiction and tolerance, Medicine (United Kingdom), Vol: 48, Pages: 749-753, ISSN: 1357-3039

Substances of abuse dysregulate key brain systems involved in motivation, reward, decision-making and memory. As drug use evolves into a compulsive addiction, there are adaptations in these systems, mediated by a number of different neurotransmitters. The mesolimbic dopaminergic pathway plays a central role in the pleasurable and positive reinforcing effects of drugs. As an individual becomes addicted, there is a shift away from this positive reinforcement to the compulsive, habitual drug-seeking behaviours driven, for example, by cravings or withdrawal symptoms. Although the potential for addiction is common with all drugs of abuse, the underlying mechanisms, neurotransmission systems and adaptations vary between drugs. This review focuses on the neurobiology of addiction and tolerance for alcohol, benzodiazepines, opioids and stimulants.

Journal article

Venkataraman A, Turton S, Lingford-Hughes A, 2020, Drug use and associated neuropsychiatric conditions, Oxford Textbook of Neuropsychiatry, Publisher: Oxford University Press, ISBN: 9780198757139

The book meets curriculum requirements for various international training programmes and examinations, and serves as an essential training text book for all psychiatric and neurology trainees worldwide.

Book chapter

Turton S, Myers J, Mick I, Colasanti A, Venkataraman A, Durant C, Waldman A, Brailsford A, Parkin M, Rabiner EA, Gunn R, Lightman S, Nutt D, Lingford-Hughes ARet al., 2020, Blunted endogenous opioid release following an oral dexamphetamine challenge in abstinent alcohol dependent individuals, Molecular Psychiatry, Vol: 25, Pages: 1749-1758, ISSN: 1359-4184

Addiction has been proposed as a ‘reward deficient’ state, which is compensated for with substance use. There is growing evidence of dysregulation in the opioid system, which plays a key role in reward, underpinning addiction. Low levels of endogenous opioids are implicated in vulnerability for developing alcohol dependence (AD) and high mu-opioid receptor (MOR) availability in early abstinence is associated with greater craving. This high MOR availability is proposed to be the target of opioid antagonist medication to prevent relapse. However, changes in endogenous opioid tone in AD are poorly characterised and are important to understand as opioid antagonists do not help everyone with AD. We used [11C]carfentanil, a selective MOR agonist positron emission tomography (PET) radioligand, to investigate endogenous opioid tone in AD for the first time. We recruited 13 abstinent male AD and 15 control participants who underwent two [11C]carfentanil PET scans, one before and one 3 h following a 0.5 mg/kg oral dose of dexamphetamine to measure baseline MOR availability and endogenous opioid release. We found significantly blunted dexamphetamine-induced opioid release in 5 out of 10 regions-of-interest including insula, frontal lobe and putamen in AD compared with controls, but no significantly higher MOR availability AD participants compared with HC in any region. This study is comparable to our previous results of blunted dexamphetamine-induced opioid release in gambling disorder, suggesting that this dysregulation in opioid tone is common to both behavioural and substance addictions.

Journal article

Erritzoe D, Ashok AH, Searle GE, Colasanti A, Turton S, Lewis Y, Huiban M, Moz S, Passchier J, Saleem A, Beaver J, Lingford-Hughes A, Nutt DJ, Howes O, Gunn RN, Knudsen GM, Rabiner Eet al., 2020, Serotonin release measured in the human brain: A PET study with [11C]CIMBI-36 and d-amphetamine challenge, Neuropsychopharmacology, Vol: 45, Pages: 804-810, ISSN: 0893-133X

Positron emission tomography (PET) enables non-invasive estimation of neurotransmitter fluctuations in the living human brain. While these methods have been applied to dopamine and some other transmitters, estimation of 5-hydroxytryptamine (5-HT; Serotonin) release has proved to be challenging. Here we demonstrate the utility of the novel 5-HT2A receptor agonist radioligand, [11C]CIMBI-36, and a d-amphetamine challenge to evaluate synaptic 5-HT changes in the living human brain. Seventeen healthy male volunteers received [11C]CIMBI-36 PET scans before and 3 hours after an oral dose of d-amphetamine (0.5 mg/kg). Dynamic PET data were acquired over 90 minutes, and the total volume of distribution (VT) in the frontal cortex and the cerebellum derived from a kinetic analysis using MA1. The frontal cortex binding potential (BPNDfrontal) was calculated as (VTfrontal/VTcerebellum)-1. BPNDfrontal = 1- (BPNDfrontalpost-dose/ BPNDfrontalbaseline) was used as an index of 5-HT release. Statistical inference was tested by means of a paired Students t-test evaluating a reduction in post-amphetamine [11C]CIMBI-36 BPNDfrontal .Following d-amphetamine administration, [11C]CIMBI-36 BPNDfrontal was reduced by 14 ± 13 % (p = 0.002). Similar effects were observed in other cortical regions examined in an exploratory analysis.[11C]CIMBI-36 binding is sensitive to synaptic serotonin release in the human brain, and when combined with a d-amphetamine challenge, the evaluation of the human brain serotonin system in neuropsychiatric disorders, such as major depression and Parkinson’s disease is enabled.

Journal article

Limbrick-Oldfield EH, Mick I, Cocks RE, Flechais RSA, Turton S, Lingford-Hughes A, Bowden-Jones H, Clark Let al., 2020, Neural and neurocognitive markers of vulnerability to gambling disorder: a study of unaffected siblings, Neuropsychopharmacology, Vol: 45, Pages: 292-300, ISSN: 0893-133X

Psychological and neurobiological markers in individuals with gambling disorder (GD) could reflect transdiagnostic vulnerability to addiction or neuroadaptive consequences of long-term gambling. Using an endophenotypic approach to identify vulnerability markers, we tested the biological relatives of cases with GD. Male participants seeking treatment for GD (n = 20) were compared with a male control group (n = 18). Biological siblings of cases with GD (n = 17, unrelated to the current GD group) were compared with a separate control group (n = 19) that overlapped partially with the GD control group. Participants completed a comprehensive assessment of clinical scales, neurocognitive functioning, and fMRI of unexpected financial reward. The GD group displayed elevated levels of self-report impulsivity and delay discounting, and increased risk-taking on the Cambridge Gamble Task. We did not observe impaired motor impulsivity on the stop-signal task. Siblings of GD showed some overlapping effects; namely, elevated impulsivity (negative urgency) and increased risk-taking on the Cambridge Gamble Task. We did not observe any differences in the neural response to win outcomes, either in the GD or sibling analysis compared with their control group. Within the GD group, activity in the thalamus and caudate correlated negatively with gambling severity. Increased impulsivity and risk-taking in GD are present in biological relatives of cases with GD, suggesting these markers may represent pre-existing vulnerability to GD.

Journal article

Timmermann Slater CB, Roseman L, Schartner M, Milliere R, Williams L, Erritzoe D, Muthukumaraswamy S, Ashton M, Bendrioua A, Kaur O, Turton S, Nour M, Day C, Leech R, Nutt D, Carhart-Harris Ret al., 2019, Neural correlates of the DMT experience as assessed with multivariate EEG, Scientific Reports, Vol: 9, Pages: 1-13, ISSN: 2045-2322

Studying transitions in and out of the altered state of consciousness caused by intravenous (IV) N,N-Dimethyltryptamine (DMT - a fast-acting tryptamine psychedelic) offers a safe and powerful means of advancing knowledge on the neurobiology of conscious states. Here we sought to investigate the effects of IV DMT on the power spectrum and signal diversity of human brain activity (6 female, 7 male) recorded via multivariate EEG, and plot relationships between subjective experience, brain activity and drug plasma concentrations across time. Compared with placebo, DMT markedly reduced oscillatory power in the alpha and beta bands and robustly increased spontaneous signal diversity. Time-referenced neurophenomenological analyses revealed close relationships between changes in various aspects of subjective experience and changes in brain activity. Importantly, the emergence of oscillatory activity within the delta and theta frequency bands was found to correlate with the peak of the experience - particularly its eyes-closed visual component. These findings highlight marked changes in oscillatory activity and signal diversity with DMT that parallel broad and specific components of the subjective experience, thus advancing our understanding of the neurobiological underpinnings of immersive states of consciousness.

Journal article

Timmermann C, Roseman L, Schartner M, Milliere R, Williams L, Erritzoe D, Muthukumaraswamy S, Ashton M, Bendrioua A, Kaur O, Turton S, Nour MM, Day CM, Leech R, Nutt D, Carhart-Harris Ret al., 2019, Neural correlates of the DMT experience as assessed via multivariate EEG, Publisher: Cold Spring Harbor Laboratory

<jats:title>Abstract</jats:title><jats:p>Studying transitions in and out of the altered state of consciousness caused by intravenous (IV) N,N-Dimethyltryptamine (DMT – a fast-acting tryptamine psychedelic) offers a safe and powerful means of advancing knowledge on the neurobiology of conscious states. Here we sought to investigate the effects of IV DMT on the power spectrum and signal diversity of human brain activity (6 female, 7 male) recorded via multivariate EEG, and plot relationships between subjective experience, brain activity and drug plasma concentrations across time. Compared with placebo, DMT markedly reduced oscillatory power in the <jats:italic>alpha</jats:italic> and <jats:italic>beta</jats:italic> bands and robustly increased spontaneous signal diversity. Time-referenced analyses revealed close relationships between changes in various aspects of subjective experience and changes in brain activity. Importantly, the emergence of oscillatory activity within the delta and theta frequency bands was found to correlate with the peak of the experience, and particularly its eyes-closed visual component. These findings highlight marked changes in oscillatory activity and signal diversity with DMT that parallel broad and specific components of the relevant subjective experience and thus further our understanding of the neurobiological underpinnings of immersive states of consciousness.</jats:p>

Working paper

Lingford-Hughes A, Durant C, Paterson L, Turton S, Venkataraman A, Wilson S, Myers J, Muthukumaraswamy S, Mick I, Paterson S, Jones T, Nahar L, Cordero R, Nutt Det al., 2018, Using baclofen to explore GABA-B receptor function in alcohol dependence: insights from pharmacokinetic and pharmacodynamic measures, Frontiers in Psychiatry, Vol: 9, ISSN: 1664-0640

Background: The role of GABA-B neurotransmission in addiction has recently received increased attention, with clinical trials indicating that baclofen, a GABA-B receptor agonist, may reduce alcohol consumption, craving and promote abstinence. However, the optimal dose to treat alcohol dependence is unclear with patients requesting and tolerating much higher doses of baclofen, compared with other clinical uses. We assessed the pharmacokinetics and pharmacodynamics (PK/PD) of baclofen to provide insight into GABA-B sensitivity in this patient group, relative to controls.Methods: Male healthy volunteers (controls, n = 12) and abstinent alcohol dependent individuals (AD, n = 8) received single oral doses of baclofen or placebo in a 3-way crossover design. Controls received placebo/10 mg/60 mg baclofen in a randomized, double-blind design, AD received placebo/60 mg/90 mg baclofen in a single-blind design. PK/PD measures were recorded at baseline and multiple time-points up to 6 h post-dosing, including plasma baclofen, plasma growth hormone (GH), Subjective High Assessment Scale (SHAS) and biphasic alcohol effects scale (BAES). Repeated measures ANOVA analysis explored “change from baseline” dose, time, group, and interaction effects, t-tests compared peak effects.Results: Dose-dependent effects of baclofen on PK and PD measures were observed in both control and AD groups. Whilst there were no significant group differences in any baclofen PK parameters (t1/2, tmax, Cmax, AUC), marked differences in PD effects were clearly evident. In controls, 60 mg baclofen significantly increased total SHAS and BAES scores, and significantly increased plasma GH levels compared with placebo, with peak effects at 60–120 min, in line with its PK profile. In AD, 60 mg baclofen had limited effects on these parameters; SHAS scores, BAES scores and plasma GH levels were significantly blunted compared with controls (significant group*time interactions P = 0.0014, 0.0015 and P

Journal article

Tyacke R, Myers J, Venkataraman A, Mick I, Turton S, Passchier J, Husbands S, Rabiner EA, Gunn R, Murphy P, Parker C, Nutt Det al., 2018, Evaluation of 11C-BU99008, a positron emission tomography ligand for the Imidazoline2 binding site in human brain, Journal of Nuclear Medicine, Vol: 59, Pages: 1597-1602, ISSN: 1535-5667

The imidazoline2 binding sites (I2BS), are thought to be expressed in glia, and implicated in the regulation of glial fibrillary acidic protein. A positron emission tomography (PET) ligand for this target would be important for the investigation of neurodegenerative and neuroinflammatory diseases. 11C BU99008 has previously been identified as a putative PET radioligand. Here we present the first in vivo characterisation of this PET radioligand in humans and assess its test-retest reproducibility. Methods: 14 healthy male volunteers underwent dynamic PET imaging with 11C BU99008 and arterial sampling. Six subjects were used to assess test-retest and eight were used in the pharmacological evaluation, undergoing a second, or third heterologous competition scan with the mixed I2BS/α2 adrenoceptor drug, idazoxan (n=8; 20, 40, 60 and 80 mg) and the mixed irreversible monoamine oxidase (MAO) A/B inhibitor, isocarboxazid (n=4; 50 mg), respectively. Regional time-activity data were generated from arterial plasma input functions corrected for metabolites using the most appropriate model to derive the outcome measure VT (regional total distribution volume). All image processing and kinetic analysis was performed in MIAKAT™ (www.miakat.org). Results: Brain uptake of 11C BU99008 was good with reversible kinetics and a heterogeneous distribution consistent with known I2BS expression. Model selection criteria indicated that the 2-tissue-compartment was preferred. VT estimates were high in the striatum (105±21 mL cm 3), medium in cingulate cortex (62±10 mL cm 3) and low in the cerebellum (41±7 mL cm 3). Test-retest reliability was found to be reasonable. The uptake was dose-dependently reduced by pre-treatment with idazoxan throughout the brain, with an average block across all regions of ~60% (VT≅30 mL cm 3) at the highest dose (80 mg). The median effective dose (ED50) for idazoxan was calculated as 28 mg. Uptake was not blocked by pre-treatme

Journal article

Venkataraman A, Keat N, Myers J, Turton S, Mick I, Gunn R, Rabiner E, Passchier J, Parker C, Tyacke R, Nutt Det al., 2018, First evaluation of PET-based human biodistribution and radiation dosimetry of 11C-BU99008, a tracer for imaging the imidazoline2 binding site, EJNMMI Research, Vol: 8, ISSN: 2191-219X

BackgroundWe measured whole body distribution of 11C-BU99008, a new PET biomarker for non-invasive identification of the imidazoline2 binding site. The purpose of this phase I study was to evaluate the biodistribution and radiation dosimetry of 11C-BU99008 in healthy human subjects.MethodsA single bolus injection of 11C-BU99008 (296 ± 10.5 MBq) was administered to four healthy subjects who underwent whole-body PET/CT over 120 min from the cranial vertex to the mid-thigh. Volumes of interest were drawn around visually identifiable source organs to generate time-activity curves (TAC). Residence times were determined from time-activity curves. Absorbed doses to individual organs and the whole body effective dose were calculated using OLINDA/EXM 1.1 for each subject.ResultsThe highest measured activity concentration was in the kidney and spleen. The longest residence time was in the muscle at 0.100 ± 0.023 h, followed by the liver at 0.067 ± 0.015 h and lungs at 0.052 ± 0.010 h. The highest mean organ absorbed dose was within the heart wall (0.028 ± 0.002 mGy/MBq), followed by the kidneys (0.026 ± 0.005 mGy/MBq). The critical organ was the heart wall. The total mean effective dose averaged over subjects was estimated to be 0.0056 ± 0.0004 mSv/MBq for an injection of 11C-BU99008.ConclusionsThe biodistribution of 11C-BU99008 has been shown here for the first time in humans. Our dosimetry data showed the total mean effective dose over all subjects was 0.0056 ± 0.0004 mSv/MBq, which would result in a total effective dose of 1.96 mSv for a typical injection of 350 MBq of 11C-BU99008. The effective dose is not appreciably different from those obtained with other 11C tracers.

Journal article

Wall JSS, Iqbal J, Andrews M, Teare D, Ghobrial M, Hinton T, Turton SP, Quffa L, El-Omar M, Fraser DG, Siotia A, Gunn Jet al., 2017, Development and validation of a clinical risk score to predict mortality after percutaneous coronary intervention., Open Heart, Vol: 4, ISSN: 2053-3624

Objective To develop and validate a contemporary clinical risk score to predict mortality after percutaneous coronary intervention (PCI).Methods Using data collected from patients undergoing PCI at the South Yorkshire Cardiothoracic Centre, Sheffield, UK, between January 2007 and September 2013, a risk score was developed to predict mortality. Logistic regression was used to evaluate the effect of each variable upon 30-day mortality. A backwards stepwise logistic regression model was then used to build a predictive model. The results were validated both internally and externally with data from Manchester Royal Infirmary, UK. 30-Day mortality status was determined from the UK Office of National Statistics.Results The development data set comprised 6522 patients from Sheffield. Five risk factors, including cardiogenic shock, procedural urgency, history of renal disease, diabetes mellitus and age, were statistically significant to predict 30-day mortality. The risk score was validated internally on a further 3290 patients from Sheffield and externally on 3230 patients from Manchester. The discrimination of the model was high in the development (C-statistic=0.82, 95% CI 0.79 to 0.85), internal (C-statistic=0.81, 95% CI 0.76 to 0.86) and external (C statistics=0.90, 95% CI 0.87 to 0.93) cohorts. There was no significant difference between observed and predicted mortality in any group.Conclusion This contemporary risk score reliably predicts 30-day mortality after PCI using a small number of clinical variables obtainable prior to the procedure, without knowledge of the coronary anatomy.

Journal article

Edison P, Mayers J, Calsolaro V, Fan Z, Turton S, Venkataraman A, Femminella G, Gunn R, Rabiner E, Matthews P, Tyacke R, Nutt Det al., 2017, Dementia Platform U.K. Experimental medicine: human in vivo astroglial activation in early Alzheimer’s disease, Alzheimer's and Dementia, Vol: 13, Pages: P1073-P1074, ISSN: 1552-5260

Journal article

Turton S, Lingford-Hughes A, 2016, Neurobiology and principles of addiction and tolerance, Medicine (United Kingdom), Vol: 44, Pages: 693-696, ISSN: 1357-3039

© 2016 Elsevier Ltd Substances of abuse dysregulate key brain systems involved in motivation, reward, decision-making and memory. As drug use evolves into a compulsive addiction, there are adaptations in these systems, mediated by a number of different neurotransmitters. The mesolimbic dopaminergic pathway plays a central role in the pleasurable and positive reinforcing effects of drugs. As an individual becomes addicted, there is a shift away from this positive reinforcement to the compulsive, habitual drug-seeking behaviours driven, for example, by cravings or withdrawal symptoms. Although the potential for addiction is common with all drugs of abuse, the underlying mechanisms, neurotransmission systems and adaptations vary between drugs. This review focuses on the neurobiology of addiction and tolerance for alcohol, benzodiazepines, opioids and stimulants.

Journal article

Nahar LK, Cordero R, Nutt D, Lingford-Hughes A, Turton S, Durant C, Wilson S, Paterson Set al., 2016, Validated method for the quantification of baclofen in human plasma using solid-phase extraction and liquid chromatography–tandem mass spectrometry, Journal of Analytical Toxicology, Vol: 40, Pages: 117-123, ISSN: 0146-4760

A highly sensitive and fully validated method was developed for the quantification of baclofen in human plasma. After adjusting the pH of the plasma samples using a phosphate buffer solution (pH 4), baclofen was purified using mixed mode (C8/cation exchange) solid-phase extraction (SPE) cartridges. Endogenous water-soluble compounds and lipids were removed from the cartridges before the samples were eluted and concentrated. The samples were analyzed using triple-quadrupoleliquid chromatography–tandem mass spectrometry (LC–MS-MS) with triggered dynamic multiple reaction monitoring mode for simultaneous quantification and confirmation. The assay was linear from 25 to 1,000 ng/mL (r2 > 0.999; n = 6). Intraday (n = 6) and interday (n = 15) imprecisions (% relative standard deviation) were <5%, and the average recovery was 30%. The limit of detection of the method was 5 ng/mL, and the limit of quantification was 25 ng/mL. Plasma samples from healthymale volunteers (n = 9, median age: 22) given two single oral doses of baclofen (10 and 60 mg) on nonconsecutive days were analyzed to demonstrate method applicability.

Journal article

Turton S, Durant C, Wilson S, Cordero R, Nahar L, Paterson S, Nutt D, Lingford-Hughes Aet al., 2015, GABA-B receptor function in healthy volunteers, a pharmacokinetic and pharmacodynamic study of two doses of baclofen compared to placebo

AIMS AND HYPOTHESISTo assess the subjective and objective effects of baclofen on brain function in healthy volunteers. BACKGROUNDRecent evidence suggests baclofen, a γ-aminobutyric acid type B (GABA-B) receptor agonist, reduces alcohol consumption and craving and promotes abstinence in alcoholics. However, characterisation of the GABA-B receptor system in clinical addiction is limited, and it is unclear why some patients require, or tolerate, higher doses to treat alcoholism. This study assesses the effects of baclofen on brain function in healthy volunteers to inform future studies investigating the sensitivity of GABA-B receptors in alcohol addiction. METHODSEight healthy male volunteers completed a double blind randomised 3-way cross over study, receiving oral placebo (vitamin C 100mg), 10mg and 60mg baclofen. Subjective and objective measurements were taken at baseline (before medication) and at +30mins, 1, 2, 3, 4 and 6 hours after dosing. Objective measures included blood plasma samples, heart rate and blood pressure. Subjective measures included; the Subjective High Assessment Questionnaire (SHAS), visual analogue scales for sleepy, relaxed, tense and alert and a motor coordination task (zig-zag task). Pharmacokinetic data was obtained using liquid chromatography mass-spectrometry (LC-MS) to measure plasma baclofen concentrations.RESULTS60mg Baclofen showed changes in subjective measures peaking at 2 hours post dosing compared with placebo, including a significant increase (p<0.05) in total SHAS scores with individual items, including feeling ‘drunk or intoxicated’, effects of alcohol and ‘muddled or confused’ particular affected.. Systolic blood pressure was significantly increased (p<0.05) at the 2 hours post 60mg dose. For both 10mg and 60mg baclofen, peak plasma concentration was achieved 60 minutes post dose. Pharmacokinetic data will be presented. There were no significant changes in these measures between 10mg Baclof

Poster

Turton SP, Nutt DJ, Carhart-Harris RL, 2014, A Qualitative Report on the Subjective Experience of Intravenous Psilocybin Administered in an fMRI Environment., Curr Drug Abuse Rev, Vol: 7, Pages: 117-127, ISSN: 1874-4737

Background: This report documents the phenomenology of the subjective experiences of 15 healthy psychedelic experienced volunteers who were involved in a functional magnetic resonance imaging (fMRI) study that was designed to image the brain effects of intravenous psilocybin. Methods: The participants underwent a semi-structured interview exploring the effects of psilocybin in the MRI scanner. These interviews were analysed by Interpretative Phenomenological Analysis. The resultant data is ordered in a detailed matrix, and presented in this paper. Results: Nine broad categories of phenomenology were identified in the phenomenological analysis of the experience; perceptual changes including visual, auditory and somatosensory distortions, cognitive changes, changes in mood, effects of memory, spiritual or mystical type experiences, aspects relating to the scanner and research environment, comparisons with other experiences, the intensity and onset of effects, and individual interpretation of the experience. Discussion: This article documents the phenomenology of psilocybin when given in a novel manner (intravenous injection) and setting (an MRI scanner). The findings of the analysis are consistent with previous published work regarding the subjective effects of psilocybin. There is much scope for further research investigating the phenomena identified in this paper.

Journal article

Turton S, Carhart-Harris R, Fielding A, Nutt Det al., 2012, Intravenously Administered Psilocybin in the fMRI environment - a phenomenological analysis, British Association for Psychopharmacology Summer Meeting

Introduction: This study aimed to investigate the phenomenology of the perceptual changes caused by the psychedelic agent psilocybin (found in ‘magic mushrooms’)when administered intravenously in a magnetic resonance imaging (MRI) scanner. The subjective effects of psilocybin have been previously documented (Pahnke, 1969,Int Psychiatry Clin 5(4):149-62, Studerus et al, 2011, J Psychopharmacol 25(11):1434-52) however, this provides an opportunity to investigate the effects when psilocybinis administered in a novel manner (intravenous injection) and setting (MRI scanner). Methods: Fifteen healthy volunteers enrolled in a study investigating the brain effectsof intravenous psilocybin using functional MRI (fMRI) imaging (Carhart-Harris et al. 2012, Proc Natl Acad Sci, 109(6):2138-2143). The study consisted of one placeboscan and a second scan during which 2mg of psilocybin were administered intravenously. Following the second fMRI scan participants underwent a semi-structuredinterview, allowing them to describe and elaborate on their experience. These interviews were fi lmed and the content analysed using an interpretative phenomenologicalanalysis methodology. Results: The peak effects of psilocybin lasted between 15-30 minutes. The two phenomenological categories that arose from the analysis consistedof experiences related to the fMRI scanner and the research environment, and experiences related to the perceptual changes caused by the psilocybin. Key componentsrelating to the scanner environment were: the scanner having a negative effect on the experience (n=11), the research environment having a negative effect on theexperience (n=11) diffi culty with the scanner noise (n=10), sense of sensory deprivation (n=8) and preferring a more ‘natural’ environment (n=9). Components relatingto the perceptual changes included visual hallucinations or distortions (n=15), physical sensations (n=12), auditory distortions (n=7), altered time perception (n=13)

Poster

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