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Psychedelic's are allowing neuroscientists to peer into the brain like never before. Thanks to modern neuroimaging techniques, scientists are not only unearthing the mechanisms by which psychedelics act on the brain and their subsequent therapeutic effects, but they are also enhancing our understanding of human consciousness.
- Modern imaging techniques (fMRI, EEG) help us understand through which mechanisms psychedelics have their influence on the brain. This helps us understand both the acute (psychedelic) effects, and how they can lead to long-term positive outcomes.
- Through the disruption of abhorrant mechanisms, for instance activity in the Default Mode Network (DMN), psychedelics can have therapeutic effects that are evident for up to years later. Several encompassing theories such as the entropic brain and its descendant REBUS help explain how this can happen at different levels.
- Neuroscience can help validate how psychedelics work and help regulators make choices about the safety (and efficacy) of psychedelics.
What is Neuroscience?
Neuroscience is the scientific study of the body’s nervous system. The nervous system is comprised of a complex network of nerves and cells that are tasked with coordinating actions and sensory information by relaying signals to and from different parts of the body. Originating in the brain, the nervous system controls one’s movements, thoughts and responses to both internal and external stimuli. Furthermore, the nervous system helps to control all other body systems.
The nervous system is subdivided into two main systems: the peripheral nervous system and the central nervous system. The central nervous system is comprised of the brain and the spinal cord. The peripheral nervous system consists of nerves that branch out from the spinal cord which connect other parts of the body to the central nervous system. Importantly, the brain is the main organ of the nervous system, acting as the body’s command centre.
The brain is a complex organ that controls thought, memory, emotion, touch, motor skills, vision, breathing, temperature, hunger and every process that regulates our body. The brain works by receiving and sending both chemical and electrical signals throughout the body as necessary. Each different region of the brain is responsible for controlling other bodily functions. For example, the hippocampus supports memory, learning and perception of space, whereas the amygdala regulates emotion and memory and is associated with the brain’s reward system .
Given the central role the brain plays in almost every aspect of our bodily functions, scientists are always seeking to better our understanding of this complex organ. To do so, scientists are always searching for new tools to peer deeper into the brain. Now, however, scientists are successfully combining modern technologies like MRI machines and EEGs with a class of psychoactive drugs that have been used throughout history, psychedelics.
Psychedelics and Neuroscience
Psychedelics are proving to be valuable tools in the realm of neuroscience. By utilizing modern technology and techniques, scientists are not only unearthing how psychedelics have the ability to produce such profound effects in the brain, but they are also helping us to better understand how psychedelics exert their therapeutic effects.
However, given that this research is in its infancy, much of the exact science remains speculative. As we progress through the psychedelic renaissance, scientists are gradually transforming these speculations into solid scientific evidence. For instance, scientists are now fairly certain that classical/serotonergic psychedelics exert their therapeutic effects, in part, by altering the brains’ default mode network (DMN).
The DMN is a network of interacting brain regions that is active when a person is not focused on the outside world, when the brain is at wakeful rest, such as during daydreaming and mind-wandering . The collection of pathways within the DMN govern our self-image, our autobiographical memories, and our deeply ingrained beliefs and thought patterns .
Abnormal functioning of the DMN has been implicated in numerous mental disorders. For example, in depression, the DMN has been shown to be hyperactive using functional MRI (fMRI). Hyperactivity in this region can lead to negative rumination, the process of continuously thinking about the same thoughts . fMRI techniques have shown that psychedelics have the ability to disrupt these engrained patterns of rumination within the DMN.
By stimulating 5-HT2A receptors, psychedelics like psilocybin downplay hyperactivity in the DMN which in turn, allows patients to work through their issues with more ease. Additionally, it appears that activation of these receptors can have long-lasting effects on brain function which enhances therapeutic outcomes . Though this view is held by many researchers, this isn’t the only mechanism at work nor should be taken as being solely responsible as a causal mechanism of psychedelics’ therapeutic effects.
Modern psychedelic neuroscience research
The research team at Imperial College London’s Centre for Psychedelic Research have been using neuroimaging techniques like fMRI to explore the effects of psychedelics on the brain for the past decade. Led by Dr. Robin Carhart-Harris, the team at Imperial have used functional neuroimaging to examine the brain under the influence of psilocybin, LSD, MDMA and DMT, as well as conducting various clinical trials into the effects psychedelics have on mental disorders.
In a 2014 seminal paper, Carhart-Harris and colleagues proposed a theory of conscious states in the brain informed by neuroimaging studies of psychedelic drugs; entropic brain theory. In short, by incorporating principles of physics, neurobiology and psychoanalysis, the theory proposes that there are two different forms of cognition that the researchers term the ‘primary’ and ‘secondary’ states.
The secondary state is our normal waking state, in which we try to limit our surprise and uncertainty about the world, or limit ‘high entropy.’ In ‘primary states,’ such as the psychedelic state, the downregulation of the DMN creates less entropy and in turn, causes the brain to enter a more critical state. In this more critical state, normal patterns of brain activity, such as those associated with mental disorders, are broken down which allows people to gain therapeutic benefit from the psychedelic experience.
Carhart-Harris and colleagues revisited their entropic brain theory in a 2018 paper, offering further evidence for this hypothesis. In 2019, Carhart-Harris combined this entropy hypothesis with a leading model of global brain function, hierarchical predictive coding. Working with Karl J. Friston, the pair termed this formulation ‘relaxed beliefs under psychedelics (REBUS) and the anarchic brain.’
The Centre for Psychedelic and Consciousness Research at Johns Hopkins University is another research group that is using psychedelics to delve into human consciousness. The centre’s director Dr. Roland Griffiths, and associate director Dr. Matthew Johnson, are two of the biggest names in the world of psychedelics.
In 2006, Griffiths and colleagues published one of the first research papers since the blanket ban on psychedelic research in the 1970s. Not only did they find that psilocybin can occasion mystical-type experiences, but these findings were also associated with long-lasting positive changes in people’s mood, attitudes and behaviour .
The findings from this study had neuroscientists across the globe wondering what the nature of these mystical experiences is and how do they elicit positive changes in people’s behaviour. In 2015, the team at Johns Hopkins were able to further validate their findings by revising the Mystical Experience Questionnaire which was developed by Walter Pahnke during the first wave of psychedelic research.
Dr. Fredrick Barrett has led numerous neuroimaging studies at Johns Hopkins investigating the effects psychedelics have on the brain. Barrett and colleagues found there to be lower functional connectivity within the DMN in trial participants who received a high dose of psilocybin. Changes in brain function were also present one day after their psilocybin experience .
Interestingly, using neuroimaging techniques, Barrett and colleagues also showed that serotonin receptor (5-HT2RA) signalling is responsible for the neural changes that occur in response to music when a person is under the influence of LSD .
More research centres exploring the effects psychedelics have on the brain, like those at Imperial and Johns Hopkins, are emerging as we progress through this third wave of psychedelic research.
A team at the University of California Davis showed that psychedelics promote structural and functional neuroplasticity in both in vitro and in vivo models . Neuroplasticity refers to the brain’s ability to modify, change, and adapt both structure and function throughout life and in response to experience and therefore, the aforementioned findings could be beneficial for mental disorders.
In March 2021, the University of California San Francisco launched The Neuroscape Psychedelic Division. Led by Dr. Robin Carhart-Harris, the team aim to investigate the positive influence of psychedelics on long-term neuroplasticity and neural network dynamics in healthy human research participants using various neuroimaging techniques.
Working with Harvard University, Massachusetts General Hospital recently opened its Center for the Neuroscience of Psychedelics to better understand how psychedelics enhance the brain’s capacity for change, optimize current treatments and create new treatments for mental illness.
Understanding the neuronal basis of how psychedelics affect the brain is essential for realizing the therapeutic potential of psychedelics. Findings from such research not only inform scientists but also regulatory bodies who are tasked with determining the safety and efficacy of psychedelic treatment models so that they can be brought to market.
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2. Voelcker-Rehage, C., Nienmann, C., Hübner, L., Godde, B., & Winneke, A. (2016). Sports and Exercise Psychology Research: From Theory to Practice. Academic Press. https://www.sciencedirect.com/science/article/pii/B9780128036341000030
3. Buckner, R., Andrews-Hanna, J., & Schacter, D. (2008). The brain’s default network: anatomy, function, and relevance to disease. Annals of The New York Academy of Sciences. https://pubmed.ncbi.nlm.nih.gov/18400922/
4. Sheline, Y., Barch, D., Price, J., Rundle, M., Snyder, A., Mintun, M., . . . Raichle, M. (2009). The default mode network and self-referential processes in depression. Proceedings of the National Academy of Sciences. https://www.pnas.org/content/106/6/1942
5. Nutt, D. (2019). Psychedelic drugs-a new era in psychiatry? Dialogues in Clinical Neuroscience, 139-147.
6. Griffiths, R., Richards, W., McCann, U., & Jesse, R. (2006). Psilocybin can occasion mystical-type experiences having substantial and sustained personal meaning and spiritual significance. Psychopharmacology.
7. Barrett, F., Johnson, M., & Griffiths, R. (2017). Psilocybin in long-term meditators: Effects on default mode network functional connectivity and retrospective ratings of qualitative experience. Drug and Alcohol Dependence. https://www.sciencedirect.com/science/article/pii/S0376871616302988
8. Barrett, F., Preller, K., Herdener, M., Janata, P., & Vollenweider, F. (2020). Serotonin 2A Receptor Signaling Underlies LSD-induced Alteration of the Neural Response to Dynamic Changes in Music. Journal of Contextual Behavioural Science.
9. Ly, C., Greb, A., Cameron, L., Wong, J., Barragan, E., Wilson, P., . . . Olson, D. (2018). Psychedelics Promote Structural and Functional Neural Plasticity. Cell Reports.
These are the institutes, from companies to universities, who are working on Neuroscience.
Johns Hopkins University (Medicine) is host to the Center for Psychedelic and Consciousness Research, which is one of the leading research institutes into psychedelics. The center is led by Roland Griffiths and Matthew Johnson.
The Centre for Psychedelic Research studies the action (in the brain) and clinical use of psychedelics, with a focus on depression.
Harvard is working with Mass General and their team at the Center for the Neuroscience of Psychedelics. Harvard Law School recently launched their POPLAR initiative.
At UCSF, there are two research teams dedicated to the study of psychedelics; the Neuroscape Psychedelic Division and the Translational Psychedelic Research Program.
These are some of the best-known people, from researchers to entrepreneurs, working on Neuroscience.
Dr. Robin Carhart-Harris is the Head of the Centre for Psychedelic Research, in the Department of Brain Sciences at Imperial College London, where he has designed a number of functional brain imaging studies with psilocybin (magic mushrooms), LSD, MDMA (ecstasy) and DMT (ayahuasca), plus clinical trials of psilocybin for treatment-resistant depression.
Roland R. Griffiths is one of the strongest voices in psychedelics research. With over 400 journal articles under his belt and as one of the first researchers in the psychedelics renaissance, he has been a vital part of the research community.
Frederick Streeter Barrett is an Assistant Professor of Psychiatry and Behavioral Sciences and works at the Johns Hopkins University Center for Psychedelic and Consciousness Research.
Matthew Johnson is an Associate Professor of Psychiatry and Behavioral Sciences at Johns Hopkins University. His research is concerned with addiction medicine, drug abuse, and drug dependence.
Linked Research Papers about Neuroscience
Psychedelic drugs-a new era in psychiatry?
Psychedelics promote structural and functional neural plasticity
Psilocybin can occasion mystical-type experiences having substantial and sustained personal meaning and spiritual significance
Psychedelic Therapy's Transdiagnostic Effects: A Research Domain Criteria (RDoC) Perspective
Psilocybin modulation of dynamic functional connectivity is associated with plasma psilocin and subjective effects
Self-Administration of Entactogen Psychostimulants Dysregulates Gamma-Aminobutyric Acid (GABA) and Kappa Opioid Receptor Signaling in the Central Nucleus of the Amygdala of Female Wistar Rats
Models of psychedelic drug action: modulation of cortical-subcortical circuits
Receptor interaction profiles of 4-alkoxy-3,5-dimethoxyphenethylamines (mescaline derivatives) and related amphetamines.
Psilocybin targets a common molecular mechanism for cognitive impairment and increased craving in alcoholism
LSD induces increased signalling entropy in rats' prefrontal cortex
Effects of Ketamine Versus Midazolam on Neurocognition at 24 Hours in Depressed Patients With Suicidal Ideation
Low-dose LSD and the stream of thought: Increased Discontinuity of Mind, Deep Thoughts and abstract flow
Bridging the Gap? Altered Thalamocortical Connectivity in Psychotic and Psychedelic States
Serotonergic Psychedelics in Neural Plasticity
Baseline power of theta oscillations predicts mystical-type experiences induced by DMT in a natural setting
Neurological and cognitive alterations induced by MDMA in humans
Low doses of LSD reduce broadband oscillatory power and modulate event-related potentials in healthy adults
Psilocin, LSD, mescaline, and DOB all induce broadband desynchronization of EEG and disconnection in rats with robust translational validity
Prefrontal contributions to the stability and variability of thought and conscious experience
Critical Period Plasticity as a Framework for Psychedelic-Assisted Psychotherapy
Neuropsychological Functioning in Users of Serotonergic Psychedelics – A Systematic Review and Meta-Analysis
The entropic brain: a theory of conscious states informed by neuroimaging research with psychedelic drugs
The entropic brain - revisited
REBUS and the Anarchic Brain: Toward a Unified Model of the Brain Action of Psychedelics
LSD degrades hippocampal spatial representations and suppresses hippocampal-visual cortical interactions
Neural Mechanisms and Psychology of Psychedelic Ego Dissolution
The effects of tryptamine psychedelics in the brain: a meta-analysis of functional and review of molecular imaging studies
Consciousness in active inference: Deep self-models, other minds, and the challenge of psychedelic-induced ego-dissolution
Psilocybin Induces Aberrant Prediction Error Processing of Tactile Mismatch Responses-A Simultaneous EEG-FMRI Study
Psychedelic resting-state neuroimaging: a review and perspective on balancing replication and novel analyses
N,N-Dimethyltryptamine attenuates spreading depolarization and restrains neurodegeneration by sigma-1 receptor activation in the ischemic rat brain
Opposite alterations of 5HT2A receptor brain density in subjects with schizophrenia: relevance of radiotracers pharmacological profile
Future Directions for Clinical Psychedelic Research: The Relaxed Symptom Network
LSD flattens the brain′s energy landscape: evidence from receptor-informed network control theory
Psychedelics and Consciousness: Distinctions, Demarcations, and Opportunities
From hallucinations to synaesthesia: a circular inference account of unimodal and multimodal erroneous percepts in clinical and drug-induced psychosis
Increased sensitivity to strong perturbations in a whole-brain model of LSD
Serotonergic psychedelic drugs LSD and psilocybin reduce the hierarchical differentiation of unimodal and transmodal cortex
A Dendrite-Focused Framework for Understanding the Actions of Ketamine and Psychedelics
LSD and ketanserin and their impact on the human autonomic nervous system
Neural Correlates of the Shamanic State of Consciousness
Effects of Acute Drug Administration on Emotion: a Review of Pharmacological MRI Studies
Effects of ketamine on brain function during metacognition of episodic memory
Neural and subjective effects of inhaled N,N-dimethyltryptamine in natural settings
Ketamine anesthesia enhances fear memory consolidation via noradrenergic activation in the basolateral amygdala
EEG Gamma Band Alterations and REM-like Traits Underpin the Acute Effect of the Atypical Psychedelic Ibogaine in the Rat
Investigation of the Structure−Activity Relationships of Psilocybin Analogues
The Effects of Daytime Psilocybin Administration on Sleep: Implications for Antidepressant Action
Subacute Effects of the Psychedelic Ayahuasca on the Salience and Default Mode Networks
Preliminary report on the effects of a low dose of LSD on resting-state amygdala functional connectivity
Dynamic coupling of whole-brain neuronal and neurotransmitter systems
Therapeutic mechanisms of psilocybin: Changes in amygdala and prefrontal functional connectivity during emotional processing after psilocybin for treatment-resistant depression
Dynamical exploration of the repertoire of brain networks at rest is modulated by psilocybin
Receptor-Enriched Analysis of functional connectivity by targets (REACT): A novel, multimodal analytical approach informed by PET to study the pharmacodynamic response of the brain under MDMA
Cytochrome P450 enzymes contribute to the metabolism of LSD to nor-LSD and 2-oxo-3-hydroxy-LSD: Implications for clinical LSD use
Oxytocin-dependent reopening of a social reward learning critical period with MDMA
Ibogaine Administration Modifies GDNF and BDNF Expression in Brain Regions Involved in Mesocorticolimbic and Nigral Dopaminergic Circuits.
Effective connectivity changes in LSD-induced altered states of consciousness in humans
Effects of Ketamine on Brain Activity During Emotional Processing: Differential Findings in Depressed Versus Healthy Control Participants
Ketamine-Associated Brain Changes: A Review of the Neuroimaging Literature
The Varieties of the Psychedelic Experience: A Preliminary Study of the Association Between the Reported Subjective Effects and the Binding Affinity Profiles of Substituted Phenethylamines and Tryptamines
Whole-brain multimodal neuroimaging model using serotonin receptor maps explains non-linear functional effects of LSD
The neurobiology of depression, ketamine and rapid-acting antidepressants: Is it glutamate inhibition or activation?
A Single Dose of 5-MeO-DMT Stimulates Cell Proliferation, Neuronal Survivability, Morphological and Functional Changes in Adult Mice Ventral Dentate Gyrus
Ketamine normalizes brain activity during emotionally valenced attentional processing in depression
Dimensions of consciousness and the psychedelic state
Pharmacological fMRI: Effects of subanesthetic ketamine on resting-state functional connectivity in the default mode network, salience network, dorsal attention network and executive control network
Ibogaine Acute Administration in Rats Promotes Wakefulness, Long-Lasting REM Sleep Suppression, and a Distinctive Motor Profile
Psilocybin modulates functional connectivity of the amygdala during emotional face discrimination
Role of the 5-HT2A Receptor in Self- and Other-Initiated Social Interaction in Lysergic Acid Diethylamide-Induced States: A Pharmacological fMRI Study
Salvinorin A preserves cerebral pial artery autoregulation after forebrain ischemia via the PI3K/AKT/cGMP pathway
Mechanisms of ketamine action as an antidepressant
Ketamine has distinct electrophysiological and behavioral effects in depressed and healthy subjects
Ketamine blocks bursting in the lateral habenula to rapidly relieve depression
Changes in global and thalamic brain connectivity in LSD-induced altered states of consciousness are attributable to the 5-HT2A receptor
Increased amygdala responses to emotional faces after psilocybin for treatment-resistant depression
Connectome-harmonic decomposition of human brain activity reveals dynamical repertoire re-organisation under LSD
The serotonin hallucinogen 5-MeO-DMT alters cortico-thalamic activity in freely moving mice: Regionally-selective involvement of 5-HT1A and 5-HT2A receptors
Ketamine’s antidepressant effect is mediated by energy metabolism and antioxidant defense system
N,N-dimethyltryptamine and the pineal gland: Separating fact from myth
Short term changes in the proteome of human cerebral organoids induced by 5-MeO-DMT
Acute LSD effects on response inhibition neural networks
MDMA Impairs Both the Encoding and Retrieval of Emotional Recollections
Inhibition of serotonin transporters disrupts the enhancement of fear memory extinction by 3,4-methylenedioxymethamphetamine (MDMA)
Two dose investigation of the 5-HT-agonist psilocybin on relative and global cerebral blood flow
MDMA-Induced Dissociative State not Mediated by the 5-HT2A Receptor
A Single Dose of LSD Does Not Alter Gene Expression of the Serotonin 2A Receptor Gene (HTR2A) or Early Growth Response Genes (EGR1-3) in Healthy Subjects
Increased spontaneous MEG signal diversity for psychoactive doses of ketamine, LSD and psilocybin
The Nucleus Accumbens and Ketamine Treatment in Major Depressive Disorder
Pharmacogenetics of ecstasy: CYP1A2, CYP2C19, and CYP2B6 polymorphisms moderate pharmacokinetics of MDMA in healthy subjects
Effects of the Natural β-Carboline Alkaloid Harmine, a Main Constituent of Ayahuasca, in Memory and in the Hippocampus: A Systematic Literature Review of Preclinical Studies
Ketamine Treatment and Global Brain Connectivity in Major Depression
The Endogenous Hallucinogen and Trace Amine N,N-Dimethyltryptamine (DMT) Displays Potent Protective Effects against Hypoxia via Sigma-1 Receptor Activation in Human Primary iPSC-Derived Cortical Neurons and Microglia-Like Immune Cells
Glutamate and gamma-aminobutyric acid systems in the pathophysiology of major depression and antidepressant response to ketamine
NMDAR inhibition-independent antidepressant actions of ketamine metabolites
LSD alters eyes-closed functional connectivity within the early visual cortex in a retinotopic fashion
Ayahuasca: pharmacology, neuroscience and therapeutic potential
Meta-analysis of executive functioning in ecstasy/polydrug users
Oxytocin receptor gene variation predicts subjective responses to MDMA
Time course of pharmacokinetic and hormonal effects of inhaled high-dose salvinorin A in humans
The serotonergic hallucinogen 5-methoxy-N,N-dimethyltryptamine disrupts cortical activity in a regionally-selective manner via 5-HT1A and 5-HT2A receptors
Modulatory effect of the 5-HT1A agonist buspirone and the mixed non-hallucinogenic 5-HT1A/2A agonist ergotamine on psilocybin-induced psychedelic experience
Behavioral and pharmacokinetic interactions between monoamine oxidase inhibitors and the hallucinogen 5-methoxy-NN-dimethyltryptamine
Serotonergic Hallucinogen-Induced Visual Perceptual Alterations
New World Tryptamine Hallucinogens and the Neuroscience of Ayahuasca
Neuroimaging in moderate MDMA use: A systematic review
Acute Biphasic Effects of Ayahuasca
Acute ketamine challenge increases resting state prefrontal-hippocampal connectivity in both humans and rats
Restructuring consciousness -the psychedelic state in light of integrated information theory
Salvinorin-A induces intense dissociative effects, blocking external sensory perception and modulating interoception and sense of body ownership in humans
Ketamine-induced modulation of the thalamo-cortical network in healthy volunteers as a model for schizophrenia
Ketamine induces a robust whole-brain connectivity pattern that can be differentially modulated by drugs of different mechanism and clinical profile
The psychedelic state induced by ayahuasca modulates the activity and connectivity of the default mode network
Antidepressant actions of ketamine: from molecular mechanisms to clinical practice
Recent advances in the neuropsychopharmacology of serotonergic hallucinogens
The role of 5-HT2A, 5-HT2C and mGlu2 receptors in the behavioral effects of tryptamine hallucinogens N,N-dimethyltryptamine and N,N-diisopropyltryptamine in rats and mice
(R,S)-Ketamine metabolites (R,S)-norketamine and (2S,6S)-hydroxynorketamine increase the mammalian target of rapamycin function
Pharmacology of Hallucinations: Several Mechanisms for One Single Symptom?
Hallucinogen persisting perception disorder and the serotonergic system: A comprehensive review including new MDMA-related clinical cases
Interaction of psychoactive tryptamines with biogenic amine transporters and serotonin receptor subtypes
Classical hallucinogens as antidepressants? A review of pharmacodynamics and putative clinical roles
Reviewing the ketamine model for schizophrenia
Serotonergic hyperactivity as a potential factor in developmental, acquired and drug-induced synesthesia
Broadband Cortical Desynchronization Underlies the Human Psychedelic State
The default-mode, ego-functions and free-energy: a neurobiological account of Freudian ideas
When the endogenous hallucinogenic trace amine N, N-dimethyltryptamine meets the sigma-1 receptor
The pharmacology of lysergic acid diethylamide: a review
Serotonin research: contributions to understanding psychoses
Effects of varied doses of psilocybin on time interval reproduction in human subjects
Glutamate and the Neural Basis of the Subjective Effects of Ketamine: A Pharmaco–Magnetic Resonance Imaging Study
The effects of the preferential 5-HT2A agonist psilocybin on prepulse inhibition of startle in healthy human volunteers depend on interstimulus interval
Hallucinogens recruit specific cortical 5-HT(2A) receptor-mediated signaling pathways to affect behavior
Effects of the South American psychoactive beverage ayahuasca on regional brain electrical activity in humans: a functional neuroimaging study using low-resolution electromagnetic tomography
Effects of ayahuasca on sensory and sensorimotor gating in humans as measured by P50 suppression and prepulse inhibition of the startle reflex, respectively
Topographic pharmaco-EEG mapping of the effects of the South American psychoactive beverage ayahuasca in healthy volunteers
The pharmacology of psilocybin
Psychopathological, neuroendocrine and autonomic effects of 3,4-methylenedioxyethylamphetamine (MDE), psilocybin and d-methamphetamine in healthy volunteers: results of an experimental double-blind placebo-controlled study
Psychedelic Effects of Ketamine in Healthy Volunteers: Relationship to Steady-state Plasma Concentrations
Mental changes experimentally produced by d-lysergic acid diethylamide tartrate