Psilocybin enhances insightfulness in meditation: a perspective on the global topology of brain imaging during meditation.

In this study, for the first time, we explored a dataset of functional magnetic resonance images collected during focused attention and open monitoring meditation before and after a five-day psilocybin-assisted meditation retreat using a recently established approach, based on the Mapper algorithm from topological data analysis. After generating subject-specific maps for two groups (psilocybin vs. placebo, 18 subjects/group) of experienced meditators, organizational principles were uncovered using graph topological tools, including the optimal transport (OT) distance, a geometrically rich measure of similarity between brain activity patterns. This revealed characteristics of the topology (i.e. shape) in space (i.e. abstract space of voxels) and time dimension of whole-brain activity patterns during different styles of meditation and psilocybin-induced alterations. Most interestingly, we found that (psilocybin-induced) positive derealization, which fosters insightfulness specifically when accompanied by enhanced open-monitoring meditation, was linked to the OT distance between open-monitoring and resting state. Our findings suggest that enhanced meta-awareness through meditation practice in experienced meditators combined with potential psilocybin-induced positive alterations in perception mediate insightfulness. Together, these findings provide a novel perspective on meditation and psychedelics that may reveal potential novel brain markers for positive synergistic effects between mindfulness practices and psilocybin.

Psychedelic Therapy: A Primer for Primary Care Clinicians-Psilocybin.

BACKGROUND: The primary psychoactive drug in magic mushrooms, psilocybin, induces profound alterations in consciousness through the 5-HT2A receptor. This review consolidates current research findings to elucidate the pharmacology, safety profile, and clinical applications of psilocybin. AREAS OF UNCERTAINTY: Despite initial concerns that psilocybin could cause psychosis, contemporary research has demonstrated that psilocybin is generally safe. The most common adverse effects are nausea and headache, yet both tend to be transient. Serious adverse events can generally be avoided in controlled settings such as clinical trials. However, in the largest clinical trial to date, there were a total of 7 reported cases of suicidal ideation, up to 12 weeks after receiving a single 25 mg dose of psilocybin. That being said, all 7 cases did not respond to the treatment. Although selective serotonin reuptake inhibitors may blunt the hallucinogenic qualities of psilocybin, preliminary research suggests that they may enhance its antidepressant effects. THERAPEUTIC ADVANCES: In clinical trials, psilocybin has shown promise for treating major depressive disorder and treatment-resistant depression. Initial studies indicated that 42%-57% of patients underwent remission after psilocybin-assisted therapy, which suggests that psilocybin is more effective than existing antidepressant medications. Clinical data have also demonstrated that psilocybin can manage substance use disorders and end-of-life anxiety with clinical outcomes that are sustained for months and sometimes years after 1 or 2 doses. LIMITATIONS: However, larger Phase II trials with more than 100 depressed participants have shown a much smaller remission rate of 25%-29%, though these studies still observed that psilocybin causes a significant reduction in depressive symptoms. CONCLUSIONS: Aside from ketamine, psilocybin is the most clinically well-researched psychedelic drug, with trials that have enrolled hundreds of participants and multiple therapeutic applications. Phase III trials will determine whether psilocybin lives up to the promise that it showed in previous clinical trials.

The effect of casing and gypsum on the yield and psychoactive tryptamine content of Psilocybe cubensis (Earle) Singer.

Psychedelic fungi have experienced a surge in interest in recent years. Most notably, the fungal secondary metabolite psilocybin has shown tremendous promise in the treatment of various psychiatric disorders. The mushroom species that produce this molecule are poorly understood. Here we sought to examine for the first time, the response of a psilocybin-producing species Psilocybe cubensis to casing (peat moss and vermiculite) and supplementation with gypsum (calcium sulfate dihydrate), two common practices in commercial mushroom cultivation. Mycelial samples of genetically authenticated P. cubensis were used to inoculate popcorn grain bags. The fully colonized bags of popcorn grain (0.15 kg) were transferred to bins of 0.85 kg pasteurized horse manure, with or without 1 cm thick layer of casing and/or 5 % gypsum. Our results indicate that the use of a casing layer significantly increases the biological efficiency (161.5 %), by approximately four fold, in comparison to control (40.5 %), albeit with a slight delay (∼2 days) for obtaining fruiting bodies and a somewhat reduced total tryptamine content (0.85 %) as gauged by High Performance Liquid Chromatography measurements. Supplementation with both casing and gypsum, however, appears to promote maximal yields (896.6 g/kg of dried substrate), with a biological efficiency of 89.6 %, while also maintaining high total tryptamine expressions (0.95 %). These findings, revealing methods for maximizing yield of harvest and expressions of psychoactive tryptamines, may prove useful for both home growers and commercial cultivators of this species, and ultimately support the growth of a robust industry with high quality natural products.

CCH attack frequency reduction after psilocybin correlates with hypothalamic functional connectivity.

OBJECTIVE: To evaluate the feasibility and prophylactic effect of psilocybin as well as its effects on hypothalamic functional connectivity (FC) in patients with chronic cluster headache (CCH). BACKGROUND: CCH is an excruciating and difficult-to-treat disorder with incompletely understood pathophysiology, although hypothalamic dysfunction has been implicated. Psilocybin may have beneficial prophylactic effects, but clinical evidence is limited. METHODS: In this small open-label clinical trial, 10 patients with CCH were included and maintained headache diaries for 10 weeks. Patients received three doses of peroral psilocybin (0.14 mg/kg) on the first day of weeks five, six, and seven. The first 4 weeks served as baseline and the last 4 weeks as follow-up. Hypothalamic FC was determined using functional magnetic resonance imaging the day before the first psilocybin dose and 1 week after the last dose. RESULTS: The treatment was well tolerated. Attack frequency was reduced by mean (standard deviation) 31% (31) from baseline to follow-up (pFWER = 0.008). One patient experienced 21 weeks of complete remission. Changes in hypothalamic-diencephalic FC correlated negatively with a percent change in attack frequency (pFWER = 0.03, R = -0.81), implicating this neural pathway in treatment response. CONCLUSION: Our results indicate that psilocybin may have prophylactic potential and implicates the hypothalamus in possible treatment response. Further clinical studies are warranted.

Antidepressant- and anxiolytic-like activities and acute toxicity evaluation of the Psilocybe cubensis mushroom in experimental models in mice.

ETHNOPHARMACOLOGY RELEVANCE: Central nervous system (CNS) diseases can be diverse and usually present with comorbidity, as in the case of depression and anxiety. Despite alternatives like Psilocybe mushrooms for mental health there is no basic research to evidence their CNS benefits. AIM OF THE STUDY: To evaluate the anxiolytic- and antidepressant-like effects, as well as the acute toxicity of P. cubensis mushroom. MATERIAL AND METHODS: First, the acute toxicity (LD50) of P. cubensis (2000 mg/kg) was determined after the esophageal (p.o.) and intraperitoneal (i.p.) route of administration. The rota-rod test and electroencephalogram (EEG) were included to assess CNS toxicity in free moving mice. Anxiolytic (ambulatory or exploratory and rearing behaviors) and antidepressant behavioral responses were assayed in the open-field, plus-maze, and forced swimming test, respectively, after administration of 1000 mg/kg, p.o., of the whole P. cubensis mushroom or the polar aqueous (AQ) or methanolic (MeOH) extractions (1, 10, and/or 100 mg/kg, i.p.) in comparison to the reference drugs buspirone (4 mg/kg, i.p.), fluoxetine and/or imipramine (10 mg/kg, s.c. and i.p., respectively). A chemical analysis of the AQ and MeOH extractions was performed to detect psilocybin and/or psilocin by using UHPLC. RESULTS: Neurotoxic effects of P. cubensis mushroom administered at high doses were absent in mice assessed in the rota-rod test or for EEG activity. A LD50 > 2000 mg/kg was calculated by p.o. or i.p. administration. While significant and/or dose-response antidepressant-like effects were produced with the whole P. cubensis mushroom, p.o., and after parenteral administration of the AQ or MeOH extractions resembling the effects of the reference drugs. Behavioral responses were associated with an anxiolytic-like effect in the open-field as corroborated in the plus-maze tests. The presence of psilocybin and psilocin was mainly characterized in the AQ extraction. CONCLUSION: Our results provide preclinical evidence of the anxiolytic- and antidepressant-like effects of the P. cubensis mushroom without producing neurotoxicity after enteral or parenteral administration, where psilocybin and psilocin were identified mainly after AQ extraction. This study reinforces the benefits of the P. cubensis mushroom in mental health and therapy for anxiety and depression.

[Psychedelics and treatment of mental disorders: A survey of attitudes and knowledge among psychiatrists, general practitioners and psychologists in Iceland].

INTRODUCTION: Interest in the use of psychedelics has increased following reports of their possible therapeutic potential. However, little is known about the knowledge of and attitudes towards the substances among health care professional who provide treatment for mental disorders in Iceland. An online survey was therefore conducted among members of the Icelandic associations of psychiatrists, general practitioners and psychologists. METHODS: Respondents were 256 in total, including 177 psychologists, 38 psychiatrists and 41 general practitioners that provided information on their background, type of work, knowledge of and attitude towards different types of psychedelic substances and their views on optimal service delivery if psychedelics were approved by licencing authorities and used for treatment. RESULTS: Around half of psychiatrists reported having received questions about treatment with psychedelics in their clinical work, compared to only 14,6% of general practitioners and 17,5% of psychologists. The majority of respondents had little, or no knowledge of the substances targeted in the survey. A majority also expressed negative attitudes towards treatment with psilocybin mushrooms, but was positive towards ongoing scientific research and felt that such a treatment should be prescribed and provided by psychiatrists. Moreover, the majority view was that psilocybin treatment should be provided in specialised clinics or psychiatric units in a hospital setting. Scientific articles on the topic, discussions with colleagues and information in the media were identified as having had most influence on respondents´ attitudes towards psychedelics. Most respondents were interested in further education on psychedelics. CONCLUSIONS: Respondents among these three professions felt that the time has not yet come to use psychedelics in the treatment of mental disorders in Iceland but thought more education on psychedelics, their potential efficacy and adverse health effects is important given the increased interest in psychedelics.

Potential use of psilocybin drugs in the treatment of depression.

INTRODUCTION: Depression is a common disabling psychiatric disorder, which - in extreme cases - may lead to suicide if untreated or inadequately treated. Despite the availability of various treatments for depression, including pharmacotherapy, there is still a need to search for new agents with higher effectiveness and faster onset of action, especially for patients with treatment-resistant depression. AREAS COVERED: A substance that has attracted considerable attention for nearly a decade is psilocybin, a natural psychedelic found in psilocybin mushrooms. In this study, we evaluated the efficacy and safety of psilocybin in the treatment of depression, based on pivotal randomized clinical trials. Moreover, we used findings from observational studies regarding recreational use. We also looked at ongoing clinical trials and discussed the registration status and clinical potential of the drug. EXPERT OPINION: Clinical phase I-II trials published to date reported promising results for psilocybin in the treatment of patients with major depressive disorder and treatment-resistant depression, in a relatively short time after administration. However, before psilocybin is approved for use and administered to patients with depression, the results of large ongoing phase III clinical trials are needed to confirm its efficacy and safety and to change the way it is perceived by physicians and patients.

Psilocybin-assisted therapy for depression: A systematic review and dose-response meta-analysis of human studies.

Psilocybin is increasingly studied for its antidepressant effect, but its optimal dosage for depression remains unclear. We conducted a systematic review and a dose-response meta-analysis to find the optimal dosage of psilocybin to reduce depression scores. Following our protocol (CRD 42022220190) multiple electronic databases were searched from their inception until February 2023, to identify double-blind randomized placebo-controlled (RCTs) fixed-dose trials evaluating the use of psilocybin for adult patients with primary or secondary depression. A one-stage dose-response meta-analysis with restricted cubic splines was used. Cochrane risk of bias was used to assess risk of bias. Our analysis included seven studies with a total of 489 participants. Among these, four studies focused on primary depression (N = 366), including one study with patients suffering from treatment-resistant depression. The remaining three studies examined secondary depression (N = 123). The determined 95% effective doses per day (ED95) were 8.92, 24.68, and 36.08 mg/70 kg for patients with secondary depression, primary depression, and both subgroups, respectively. We observed significant dose-response associations for all curves, each plateauing at different levels, except for the bell-shaped curve observed in the case of secondary depression. Additionally, we found significant dose-response associations for various side effects, including physical discomfort, blood pressure increase, nausea/vomiting, headache/migraine, and the risk of prolonged psychosis. In conclusion, we discovered specific ED95 values for different populations, indicating higher ED95 values for treatment-resistant depression, primary depression, and secondary depression groups. Further RCTs are necessary for each population to determine the optimal dosage, allowing for maximum efficacy while minimizing side effects.

A Proposal to Study the Safety and Efficacy of Psilocybe cubensis in Preclinical and Clinical Studies as a Therapeutic Alternative for Major Depressive Disorder.

The pharmacological treatment of depression consists of taking antidepressant drugs for prolonged periods; its modest therapeutic effect can often be associated with significant adverse effects, while its discontinuation can lead to relapses. Psilocybin is today a novel and breakthrough therapy for major depression. It is a natural alkaloid in Psilocybe mushrooms, which are endemic to Mexico. Research on a larger scale is lacking in various populations, including the Mexican people. This proposal contemplates the experimental design of a preclinical (toxicity and pharmacological evaluation of an extract in mice) and clinical study by including the chemical analysis of a species of Psilocybe cubensis mushroom to characterize its main constituents. The clinical study will consider the safety evaluation by exploring tolerated doses of Psilocybe cubensis by measuring pharmacokinetic parameters after oral administration in healthy adults and an open trial on a sample of patients with major depressive disorder to assess the safety and efficacy of fully characterized Psilocybe cubensis in a two-single doses treatment, (with assisted psychotherapy), compared with the traditional care model at the Instituto Nacional de Psiquiatría Ramón de la Fuente Muñiz in Mexico City. This report presents the design of a research project with preclinical and clinical experimental components.

Letter to the editor on "Increased low-frequency brain responses to music after psilocybin therapy for depression".

The recent publication in the Journal of Affective Disorders titled "Increased low-frequency brain responses to music after psilocybin therapy for depression" identified significant region-of-interest based effects of treatment in the task scans. In this letter to the editor, I am hoping to raise methodological concerns with regards to the ANOVA ROI analysis that were otherwise not acknowledged in this study. These concerns raise questions as to the impact of confounds, including as age and biological sex, on the reported proportion variance explained by the effects of psilocybin treatment for depression.

Increased low-frequency brain responses to music after psilocybin therapy for depression.

BACKGROUND: Psychedelic-assisted psychotherapy with psilocybin is an emerging therapy with great promise for depression, and modern psychedelic therapy (PT) methods incorporate music as a key element. Music is an effective emotional/hedonic stimulus that could also be useful in assessing changes in emotional responsiveness following PT. METHODS: Brain responses to music were assessed before and after PT using functional Magnetic Resonance Imaging (fMRI) and ALFF (Amplitude of Low Frequency Fluctuations) analysis methods. Nineteen patients with treatment-resistant depression underwent two treatment sessions involving administration of psilocybin, with MRI data acquired one week prior and the day after completion of psilocybin dosing sessions. RESULTS: Comparison of music-listening and resting-state scans revealed significantly greater ALFF in bilateral superior temporal cortex for the post-treatment music scan, and in the right ventral occipital lobe for the post-treatment resting-state scan. ROI analyses of these clusters revealed a significant effect of treatment in the superior temporal lobe for the music scan only. Voxelwise comparison of treatment effects showed relative increases for the music scan in the bilateral superior temporal lobes and supramarginal gyrus, and relative decreases in the medial frontal lobes for the resting-state scan. ALFF in these music-related clusters was significantly correlated with intensity of subjective effects felt during the dosing sessions. LIMITATIONS: Open-label trial. Relatively small sample size. CONCLUSIONS: These data suggest an effect of PT on the brain's response to music, implying an elevated responsiveness to music after psilocybin therapy that was related to subjective drug effects felt during dosing.

Investigation of self-treatment with lysergic acid diethylamide and psilocybin mushrooms: Findings from the Global Drug Survey 2020.

BACKGROUND: Growing numbers of people are using psychedelics for personal psychotherapy outside clinical settings, but research on such use is scarce. AIMS: This study investigated the patterns of use, self-reported outcomes and outcome predictors of psychedelic 'self-treatment' of mental health conditions or specific worries/concerns in life. METHODS: We use data from the Global Drug Survey 2020, a large online survey on drug use collected between November 2019 and February 2020. In all, 3364 respondents reported their self-treatment experiences with lysergic acid diethylamide (N = 1996) or psilocybin mushrooms (N = 1368). The primary outcome of interest was the 17-item self-treatment outcome scale, items reflecting aspects of well-being, psychiatric symptoms, social-emotional skills, and health behaviours. RESULTS: Positive changes were observed across all 17 outcome items, with the strongest benefits on items related to insight and mood. Negative effects were reported by 22.5% of respondents. High intensity of psychedelic experience, seeking advice before treatment, treating with psilocybin mushrooms and treating post-traumatic stress disorder were associated with higher scores on the self-treatment outcome scale after averaging values across all 17 items. Younger age, high intensity of experience and treating with LSD were associated with increased number of negative outcomes. CONCLUSIONS: This study brings important insights into self-treatment practices with psychedelics in a large international sample. Outcomes were generally favourable, but negative effects appeared more frequent than in clinical settings. Our findings can help inform safe practices of psychedelic use in the community, and inspire clinical research. Future research can be improved with utilisation of prospective designs and additional predictive variables.

An Integrative Review of Measures of Spirituality in Experimental Studies of Psilocybin in Serious Illness Populations.

Background: Psilocybin-assisted therapies (PAT) are reemerging as a treatment for complex distress often prompting mystical experiences, enhanced meaning, and spiritual wellbeing. We sought to investigate how measures of spirituality are employed in experimental studies of PAT conducted with seriously ill adults. Methods: We included experimental studies of psilocybin conducted with seriously ill adults, which employed measures that contained spirituality and mysticism concepts within their domains or subdomains. Included studies were peer-reviewed and published in English language (up to December 2021). Results: Seven articles met our inclusion criteria. A total of 12 unique instruments were identified. The most frequently used instruments were the Mystical Experience Questionnaire (MEQ30), the Functional Assessment of Chronic Illness Therapy-Spirituality (FACIT-Sp-12), and the Demoralization Scale (DS-I/II) (used in four studies each), followed by the Persisting Effects Questionnaire (PEQ) (used in three studies). Overall, studies did not consistently define and contextualize spirituality domains and subdomains studied. Conclusions: Despite well-recognized significance of spirituality in PAT, there was considerable heterogeneity in number and types of spirituality measures employed across studies. There also seemed a lack of attention to defining and operationalizing spirituality and its domains and subdomains. This is notable as spirituality and overlapping concepts (eg mystical experiences) contributes substantially to this body of research and patients' therapeutic outcomes. Towards developing more rigorous science of spirituality in PAT research, there is a critical need to evaluate and refine measures of spirituality to enhance their utility and replicability, limit participant burden, and better contextualize spirituality-related findings and outcomes.

Linkages between Psychedelics and Meditation in a Population-Based Sample in the United States.

There are neurophysiological and phenomenological overlaps between psychedelic and meditative states, but there is little evidence on how exposure to psychedelics might be associated with meditation-related variables. We assessed lifetime classic psychedelic use, ego dissolution during one's most intense experience using a classic psychedelic, and exposure to meditation in a representative sample (n = 953) of American adults. Those who reported experience with meditation were invited to complete a follow-up survey (n = 536, 92.1% response rate) measuring meditation-related variables. Models controlled for a range of potential confounds. Exposure to meditation was associated with lifetime classic psychedelic use and ego dissolution in covariate-adjusted models. In addition, among meditators, greater ego dissolution was associated with more frequent meditation practice. Both lifetime classic psychedelic use and ego dissolution were associated with enlightenment as motivation to practice meditation as well as lower likelihood of overall perceived barriers to meditation practice. Ego dissolution was positively associated with finding meditation more effective. Neither lifetime classic psychedelic use nor ego dissolution was associated with greater likelihood of meditation-related adverse effects. Taken together, results support potential synergy between psychedelics and meditation, but randomized controlled trials are necessary to establish safety and evaluate potential causal relationships.

Psychotherapists' openness to engage their patients in Psilocybin-Assisted Therapy for mental health treatment.

Despite psychedelic research initially ceasing in the 1970-80s, the findings documented encouraged researchers to re-examine the safety and efficacy of treating mental health with psychedelics. Of particular focus, psilocybin has shown to have therapeutic potential for a variety of mental health problems and was granted breakthrough therapy status by the FDA. Should psilocybin eventually become legally licensed, the success of Psilocybin-Assisted Therapy (PAT) may largely rely on clinicians' openness to engage their eligible patients with PAT. We therefore assessed 119 psychologists' openness to recommend PAT, perceived barriers/facilitators to informing patients about PAT, and factors affecting their openness to involve patients with PAT if FDA approved. While 77.4 % of psychologists agreed they would inform eligible patients about PAT, 91.6 % stated they would still recommend psychotherapies that do not involve psilocybin first. 76.5 % endorsed that knowledge on psilocybin would increase their likelihood to inform patients about PAT. More positive attitudes and beliefs about psilocybin, greater self-reported knowledge of psilocybin, personal history of psychedelic usage, and more positive attitudes towards medical cannabis (MC) was associated with greater openness to engage patients with PAT. Our regression analysis revealed that attitudes towards MC and beliefs about psilocybin were the only significant predictors of psychotherapists' openness towards PAT. These findings provide relevant information to institutions planning educational programs for mental health professionals about psilocybin and Psychedelic-Assisted Therapies.

Psilocybin-assisted therapy improves psycho-social-spiritual well-being in cancer patients.

BACKGROUND: While psychedelics have been shown to improve psycho-spiritual well-being, the underlying elements of this change are not well-characterized. The NIH-HEALS posits that psycho-social-spiritual change occurs through the factors of Connection, Reflection & Introspection, and Trust & Acceptance. This study aimed to evaluate the changes in NIH-HEALS scores in a cancer population with major depressive disorder undergoing psilocybin-assisted therapy. METHODS: In this Phase II, single-center, open label trial, 30 cancer patients with major depressive disorder received a fixed dose of 25 mg of psilocybin. Participants underwent group preparation sessions, simultaneous psilocybin treatment administered in adjacent rooms, and group integration sessions, along with individual care. The NIH-HEALS, a self-administered, 35-item measure of psycho-social spiritual healing was completed at baseline and post-treatment at day 1, week 1, week 3, and week 8 following psilocybin therapy. RESULTS: NIH-HEALS scores, representing psycho-social-spiritual wellbeing, improved in response to psilocybin treatment (p < 0.001). All three factors of the NIH-HEALS (Connection, Reflection & Introspection, and Trust & Acceptance) demonstrated positive change by 12.7 %, 7.7 %, and 22.4 %, respectively. These effects were apparent at all study time points and were sustained up to the last study interval at 8 weeks (p < 0.001). LIMITATIONS: The study lacks a control group, relies on a self-report measure, and uses a relatively small sample size with limited diversity that restricts generalizability. CONCLUSIONS: Findings suggest that psilocybin-assisted therapy facilitates psycho-social-spiritual growth as measured by the NIH-HEALS and its three factors. This supports the factors of Connection, Reflection & Introspection, and Trust & Acceptance as underlying elements for psycho-social-spiritual healing in cancer patients, and validates the use of the NIH-HEALS within psychedelic research.

Changes in music-evoked emotion and ventral striatal functional connectivity after psilocybin therapy for depression.

BACKGROUND: Music listening is a staple and valued component of psychedelic therapy, and previous work has shown that psychedelics can acutely enhance music-evoked emotion. AIMS: The present study sought to examine subjective responses to music before and after psilocybin therapy for treatment-resistant depression, while functional magnetic resonance imaging (fMRI) data was acquired. METHODS: Nineteen patients with treatment-resistant depression received a low oral dose (10 mg) of psilocybin, and a high dose (25 mg) 1 week later. fMRI was performed 1 week prior to the first dosing session and 1 day after the second. Two scans were conducted on each day: one with music and one without. Visual analogue scale ratings of music-evoked 'pleasure' plus ratings of other evoked emotions (21-item Geneva Emotional Music Scale) were completed after each scan. Given its role in musical reward, the nucleus accumbens (NAc) was chosen as region of interest for functional connectivity (FC) analyses. Effects of drug (vs placebo) and music (vs no music) on subjective and FC outcomes were assessed. Anhedonia symptoms were assessed pre- and post-treatment (Snaith-Hamilton Pleasure Scale). RESULTS: Results revealed a significant increase in music-evoked emotion following treatment with psilocybin that correlated with post-treatment reductions in anhedonia. A post-treatment reduction in NAc FC with areas resembling the default mode network was observed during music listening (vs no music). CONCLUSION: These results are consistent with current thinking on the role of psychedelics in enhancing music-evoked pleasure and provide some new insight into correlative brain mechanisms.

Psilocybin induces spatially constrained alterations in thalamic functional organizaton and connectivity.

BACKGROUND: Classic psychedelics, such as psilocybin and LSD, and other serotonin 2A receptor (5-HT2AR) agonists evoke acute alterations in perception and cognition. Altered thalamocortical connectivity has been hypothesized to underlie these effects, which is supported by some functional MRI (fMRI) studies. These studies have treated the thalamus as a unitary structure, despite known differential 5-HT2AR expression and functional specificity of different intrathalamic nuclei. Independent Component Analysis (ICA) has been previously used to identify reliable group-level functional subdivisions of the thalamus from resting-state fMRI (rsfMRI) data. We build on these efforts with a novel data-maximizing ICA-based approach to examine psilocybin-induced changes in intrathalamic functional organization and thalamocortical connectivity in individual participants. METHODS: Baseline rsfMRI data (n=38) from healthy individuals with a long-term meditation practice was utilized to generate a statistical template of thalamic functional subdivisions. This template was then applied in a novel ICA-based analysis of the acute effects of psilocybin on intra- and extra-thalamic functional organization and connectivity in follow-up scans from a subset of the same individuals (n=18). We examined correlations with subjective reports of drug effect and compared with a previously reported analytic approach (treating the thalamus as a single functional unit). RESULTS: Several intrathalamic components showed significant psilocybin-induced alterations in spatial organization, with effects of psilocybin largely localized to the mediodorsal and pulvinar nuclei. The magnitude of changes in individual participants correlated with reported subjective effects. These components demonstrated predominant decreases in thalamocortical connectivity, largely with visual and default mode networks. Analysis in which the thalamus is treated as a singular unitary structure showed an overall numerical increase in thalamocortical connectivity, consistent with previous literature using this approach, but this increase did not reach statistical significance. CONCLUSIONS: We utilized a novel analytic approach to discover psilocybin-induced changes in intra- and extra-thalamic functional organization and connectivity of intrathalamic nuclei and cortical networks known to express the 5-HT2AR. These changes were not observed using whole-thalamus analyses, suggesting that psilocybin may cause widespread but modest increases in thalamocortical connectivity that are offset by strong focal decreases in functionally relevant intrathalamic nuclei.