OPEN Foundation

F. Vollenweider

Psilocybin exerts distinct effects on resting state networks associated with serotonin and dopamine in mice

Abstract

Hallucinogenic agents have been proposed as potent antidepressants; this includes the serotonin (5-HT) receptor 2A agonist psilocybin. In human subjects, psilocybin alters functional connectivity (FC) within the default-mode network (DMN), a constellation of inter-connected regions that displays altered FC in depressive disorders. In this study, we investigated the effects of psilocybin on FC across the entire brain with a view to investigate underlying mechanisms. Psilocybin effects were investigated in lightly-anaesthetized mice using resting-state fMRI. Dual-regression analysis identified reduced FC within the ventral striatum in psilocybin- relative to vehicle-treated mice. Refinement of the analysis using spatial references derived from both gene expression maps and viral tracer projection fields revealed two distinct effects of psilocybin: it increased FC between 5-HT-associated networks and cortical areas, including elements of the murine DMN, thalamus, and midbrain; it decreased FC within dopamine (DA)-associated striatal networks. These results suggest that interactions between 5-HT- and DA-regulated neural networks contribute to the neural and therefore psychological effects of psilocybin. Furthermore, they highlight how information on molecular expression patterns and structural connectivity can assist in the interpretation of pharmaco-fMRI findings.

Grandjean, J., Buehlmann, D., Buerge, M., Sigrist, H., Seifritz, E., Vollenweider, F. X., Pryce, C. R., & Rudin, M. (2021). Psilocybin exerts distinct effects on resting state networks associated with serotonin and dopamine in mice. NeuroImage, 225, 117456. https://doi.org/10.1016/j.neuroimage.2020.117456

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Psychedelic drugs: neurobiology and potential for treatment of psychiatric disorders

Abstract

Renewed interest in the use of psychedelics in the treatment of psychiatric disorders warrants a better understanding of the neurobiological mechanisms underlying the effects of these substances. After a hiatus of about 50 years, state-of-the art studies have recently begun to close important knowledge gaps by elucidating the mechanisms of action of psychedelics with regard to their effects on receptor subsystems, systems-level brain activity and connectivity, and cognitive and emotional processing. In addition, functional studies have shown that changes in self-experience, emotional processing and social cognition may contribute to the potential therapeutic effects of psychedelics. These discoveries provide a scientific road map for the investigation and application of psychedelic substances in psychiatry.

Vollenweider, F. X., & Preller, K. H. (2020). Psychedelic drugs: neurobiology and potential for treatment of psychiatric disorders. Nature reviews. Neuroscience, 21(11), 611–624. https://doi.org/10.1038/s41583-020-0367-2

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LSD-induced increases in social adaptation to opinions similar to one’s own are associated with stimulation of serotonin receptors

Abstract

Adapting one’s attitudes and behaviors to group norms is essential for successful social interaction and, thus, participation in society. Yet, despite its importance for societal and individual functioning, the underlying neuropharmacology is poorly understood. We therefore investigated its neurochemical and neural correlates in a pharmacological functional magnetic resonance imaging study. Lysergic acid diethylamide (LSD) has been shown to alter social processing and therefore provides the unique opportunity to investigate the role of the 5-HT2A receptor in social influence processing. Twenty-four healthy human volunteers received either (1) placebo + placebo, (2) placebo + LSD (100 µg), or (3) the 5-HT2A receptor antagonist ketanserin (40 mg) + LSD (100 µg) at three different occasions in a double-blind, randomized, counterbalanced, cross-over design. LSD increases social adaptation but only if the opinions of others are similar to the individual’s own. These increases were associated with increased activity in the medial prefrontal cortex while participants received social feedback. Furthermore, pretreatment with the 5-HT2A antagonist ketanserin fully blocked LSD-induced changes during feedback processing, indicating a key role of the 5-HT2A system in social feedback processing. Our results highlight the crucial role of the 5-HT-system in social influence and, thus, provide important insight into the neuropharmacological basis of social cognition and behavior.
Duerler, P., Schilbach, L., Stämpfli, P., Vollenweider, F. X., & Preller, K. H. (2020). LSD-induced increases in social adaptation to opinions similar to one’s own are associated with stimulation of serotonin receptors. Scientific reports10(1), 1-11., https://doi.org/10.1038/s41598-020-68899-y
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Modulation of Social Cognition via Hallucinogens and "Entactogens".

Abstract

Social cognition is a fundamental ability in human everyday lives. Deficits in social functioning also represent a core aspect of many psychiatric disorders. Yet, despite its significance, deficits in social cognition skills are insufficiently targeted by current treatments. Hallucinogens and entactogens have been shown to have the potential to modulate social processing. This article reviews the literature on the influence of hallucinogens and entactogens on social processing in controlled experimental studies in humans and elucidates the underlying neurobiological and neuropharmacological mechanisms. Furthermore, it identifies current knowledge gaps and derives implications for hallucinogen-assisted treatment approaches as well as the development of novel medication for trans-diagnostic impairments in social cognition.

Preller, K. H., & Vollenweider, F. X. (2019). Modulation of Social Cognition via Hallucinogens and “Entactogens”. Frontiers in Psychiatry10., https://doi.org/10.3389/fpsyt.2019.00881
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Modulation of Social Cognition via Hallucinogens and “Entactogens”.

Abstract

Social cognition is a fundamental ability in human everyday lives. Deficits in social functioning also represent a core aspect of many psychiatric disorders. Yet, despite its significance, deficits in social cognition skills are insufficiently targeted by current treatments. Hallucinogens and entactogens have been shown to have the potential to modulate social processing. This article reviews the literature on the influence of hallucinogens and entactogens on social processing in controlled experimental studies in humans and elucidates the underlying neurobiological and neuropharmacological mechanisms. Furthermore, it identifies current knowledge gaps and derives implications for hallucinogen-assisted treatment approaches as well as the development of novel medication for trans-diagnostic impairments in social cognition.

Preller, K. H., & Vollenweider, F. X. (2019). Modulation of Social Cognition via Hallucinogens and “Entactogens”. Frontiers in Psychiatry10., https://doi.org/10.3389/fpsyt.2019.00881
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Psilocybin-assisted mindfulness training modulates self-consciousness and brain default mode network connectivity with lasting effects

Abstract

Both psychedelics and meditation exert profound modulatory effects on consciousness, perception and cognition, but their combined, possibly synergistic effects on neurobiology are unknown. Accordingly, we conducted a randomized, double-blind, placebo-controlled study with 38 participants following a single administration of the psychedelic psilocybin (315 μg/kg p.o.) during a 5-day mindfulness retreat. Brain dynamics were quantified directly pre- and post-intervention by functional magnetic resonance imaging during the resting state and two meditation forms. The analysis of functional connectivity identified psilocybin-related and mental state–dependent alterations in self-referential processing regions of the default mode network (DMN). Notably, decoupling of medial prefrontal and posterior cingulate cortices, which is thought to mediate sense of self, was associated with the subjective ego dissolution effect during the psilocybin-assisted mindfulness session. The extent of ego dissolution and brain connectivity predicted positive changes in psycho-social functioning of participants 4 months later. Psilocybin, combined with meditation, facilitated neurodynamic modulations in self-referential networks, subserving the process of meditation by acting along the anterior–posterior DMN connection. The study highlights the link between altered self-experience and subsequent behavioral changes. Understanding how interventions facilitate transformative experiences may open novel therapeutic perspectives. Insights into the biology of discrete mental states foster our understanding of non-ordinary forms of human self-consciousness and their concomitant brain substrate.

Smigielski, L., Scheidegger, M., Kometer, M., & Vollenweider, F. X. (2019). Psilocybin-assisted mindfulness training modulates self-consciousness and brain default mode network connectivity with lasting effects. NeuroImage196, 207-215., https://doi.org/10.1016/j.neuroimage.2019.04.009
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Effective connectivity changes in LSD-induced altered states of consciousness in humans

Abstract

Psychedelics exert unique effects on human consciousness. The thalamic filter model suggests that core effects of psychedelics may result from gating deficits, based on a disintegration of information processing within cortico–striato–thalamo-cortical (CSTC) feedback loops. To test this hypothesis, we characterized changes in directed (effective) connectivity between selected CTSC regions after acute administration of lysergic acid diethylamide (LSD), and after pretreatment with Ketanserin (a selective serotonin 2A receptor antagonist) plus LSD in a double-blind, randomized, placebo-controlled, cross-over study in 25 healthy participants. We used spectral dynamic causal modeling (DCM) for resting-state fMRI data. Fully connected DCM models were specified for each treatment condition to investigate the connectivity between the following areas: thalamus, ventral striatum, posterior cingulate cortex, and temporal cortex. Our results confirm major predictions proposed in the CSTC model and provide evidence that LSD alters effective connectivity within CSTC pathways that have been implicated in the gating of sensory and sensorimotor information to the cortex. In particular, LSD increased effective connectivity from the thalamus to the posterior cingulate cortex in a way that depended on serotonin 2A receptor activation, and decreased effective connectivity from the ventral striatum to the thalamus independently of serotonin 2A receptor activation. Together, these results advance our mechanistic understanding of the action of psychedelics in health and disease. This is important for the development of new pharmacological therapeutics and also increases our understanding of the mechanisms underlying the potential clinical efficacy of psychedelics.

Preller, K. H., Razi, A., Zeidman, P., Stämpfli, P., Friston, K. J., & Vollenweider, F. X. (2019). Effective connectivity changes in LSD-induced altered states of consciousness in humans. Proceedings of the National Academy of Sciences, 201815129., 10.1073/pnas.1815129116
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Changes in global and thalamic brain connectivity in LSD-induced altered states of consciousness are attributable to the 5-HT2A receptor

Abstract

BACKGROUND:

Lysergic acid diethylamide (LSD) has agonist activity at various serotonin (5-HT) and dopamine receptors. Despite the therapeutic and scientific interest in LSD, specific receptor contributions to its neurobiological effects remain unknown.

METHODS:

We therefore conducted a double-blind, randomized, counterbalanced, cross-over study (ClinicalTrials.gov, NCT02451072) during which 24 healthy human participants received either (i) placebo+placebo, (ii) placebo+LSD (100 µg po), or (iii) Ketanserin, a selective 5-HT2A receptor antagonist,+LSD. We quantified resting-state functional connectivity via a data-driven global brain connectivity method and compared it to cortical gene expression maps.

FINDINGS:

LSD reduced associative, but concurrently increased sensory-somatomotor brain-wide and thalamic connectivity. Ketanserin fully blocked the subjective and neural LSD effects. Whole-brain spatial patterns of LSD effects matched 5-HT2A receptor cortical gene expression in humans.

CONCLUSION:

Together, these results strongly implicate the 5-HT2A receptor in LSD’s neuropharmacology. This study therefore pinpoints the critical role of 5-HT2A in LSD’s mechanism, which informs its neurobiology and guides rational development of psychedelic-based therapeutics.

Preller, K. H., Burt, J. B., Ji, J. L., Schleifer, C. H., Adkinson, B. D., Stämpfli, P., … & Vollenweider, F. X. (2018). Changes in global and thalamic brain connectivity in LSD-induced altered states of consciousness are attributable to the 5-HT2A receptor. eLife7, e35082., 10.7554/eLife.35082

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Psilocybin modulates functional connectivity of the amygdala during emotional face discrimination

Abstract

Recent studies suggest that the antidepressant effects of the psychedelic 5-HT2A receptor agonist psilocybin are mediated through its modulatory properties on prefrontal and limbic brain regions including the amygdala. To further investigate the effects of psilocybin on emotion processing networks, we studied for the first-time psilocybin’s acute effects on amygdala seed-to-voxel connectivity in an event-related face discrimination task in 18 healthy volunteers who received psilocybin and placebo in a double-blind balanced cross-over design. The amygdala has been implicated as a salience detector especially involved in the immediate response to emotional face content. We used beta-series amygdala seed-to-voxel connectivity during an emotional face discrimination task to elucidate the connectivity pattern of the amygdala over the entire brain.

When we compared psilocybin to placebo, an increase in reaction time for all three categories of affective stimuli was found. Psilocybin decreased the connectivity between amygdala and the striatum during angry face discrimination. During happy face discrimination, the connectivity between the amygdala and the frontal pole was decreased. No effect was seen during discrimination of fearful faces. Thus, we show psilocybin’s effect as a modulator of major connectivity hubs of the amygdala. Psilocybin decreases the connectivity between important nodes linked to emotion processing like the frontal pole or the striatum. Future studies are needed to clarify whether connectivity changes predict therapeutic effects in psychiatric patients.

Grimm, O., Kraehenmann, R., Preller, K. H., Seifritz, E., & Vollenweider, F. X. (2018). Psilocybin modulates functional connectivity of the amygdala during emotional face discrimination. European Neuropsychopharmacology. 10.1016/j.euroneuro.2018.03.016
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Role of the 5-HT2A receptor in self- and other-initiated social interaction in LSD-induced states – a pharmacological fMRI study

Abstract

Distortions of self-experience are critical symptoms of psychiatric disorders and have detrimental effects on social interactions. In light of the immense need for improved and targeted interventions for social impairments, it is important to better understand the neurochemical substrates of social interaction abilities. We therefore investigated the pharmacological and neural correlates of self- and other-initiated social interaction. In a double-blind, randomized, counterbalanced, cross-over study 24 healthy human participants (18 males and 6 females) received either 1) placebo+placebo 2) placebo+lysergic acid diethylamide (LSD) (100 μg p.o.), or 3) ketanserin (40 mg p.o.)+LSD (100 μg p.o.) at three different occasions. Participants took part in an interactive task using eye-tracking and functional magnetic resonance imaging completing trials of self- and other-initiated joint and non-joint attention. Results demonstrate first, that LSD reduced activity in brain areas important for self-processing, but also social cognition, second that change in brain activity was linked to subjective experience, and third that LSD decreased the efficiency of establishing joint attention. Furthermore, LSD-induced effects were blocked by the serotonin 2A receptor (5-HT2AR) antagonist ketanserin, indicating that effects of LSD are attributable to 5-HT2AR stimulation. The current results demonstrate that activity in areas of the ‘social brain’ can be modulated via the 5-HT2AR thereby pointing towards this system as a potential target for the treatment of social impairments associated with psychiatric disorders.SIGNIFICANCE STATEMENTDistortions of self-representation and, potentially related to this, dysfunctional social cognition are central hallmarks of various psychiatric disorders and critically impact disease development, progression, treatment, as well as real-world functioning. However, these deficits are insufficiently targeted by current treatment approaches. The administration of lysergic acid diethylamide (LSD) in combination with functional magnetic resonance imaging and real-time eye-tracking offers the unique opportunity to study alterations in self-experience, their relation to social cognition, and the underlying neuropharmacology. Results demonstrate that LSD alters self-experience as well as basic social cognition processing in areas of the ‘social brain’. Furthermore, these alterations are attributable to 5-HT2A receptor stimulation, thereby pinpointing towards this receptor system in the development of pharmacotherapies for sociocognitive deficits in psychiatric disorders.
Preller, K. H., Schilbach, L., Pokorny, T., Flemming, J., Seifritz, E., & Vollenweider, F. X. (2018). Role of the 5-HT2A receptor in self-and other-initiated social interaction in LSD-induced states—a pharmacological fMRI study. Journal of Neuroscience, 1939-17. 10.1523/JNEUROSCI.1939-17.2018
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