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Neuroscience

Seeing with the eyes shut: Neural basis of enhanced imagery following ayahuasca ingestion

September 16, 2011 / Ayahuasca, Neuroscience, Other subjects, Papers, Psychology, Publications / By / , , , , , ,

Abstract

The hallucinogenic brew Ayahuasca, a rich source of serotonergic agonists and reuptake inhibitors, has been used for ages by Amazonian populations during religious ceremonies. Among all perceptual changes induced by Ayahuasca, the most remarkable are vivid “seeings.” During such seeings, users report potent imagery. Using functional magnetic resonance imaging during a closed-eyes imagery task, we found that Ayahuasca produces a robust increase in the activation of several occipital, temporal, and frontal areas. In the primary visual area, the effect was comparable in magnitude to the activation levels of natural image with the eyes open. Importantly, this effect was specifically correlated with the occurrence of individual perceptual changes measured by psychiatric scales. The activity of cortical areas BA30 and BA37, known to be involved with episodic memory and the processing of contextual associations, was also potentiated by Ayahuasca intake during imagery. Finally, we detected a positive modulation by Ayahuasca of BA 10, a frontal area involved with intentional prospective imagination, working memory and the processing of information from internal sources. Therefore, our results indicate that Ayahuasca seeings stem from the activation of an extensive network generally involved with vision, memory, and intention. By boosting the intensity of recalled images to the same level of natural image, Ayahuasca lends a status of reality to inner experiences. It is therefore understandable why Ayahuasca was culturally selected over many centuries by rain forest shamans to facilitate mystical revelations of visual nature.

de Aurojo, D. B., Ribeiro, S., Cecchi, G. A., Carvalho, F. M., Sanchez, T. A., Pinto, J. P., … Santos, A. C. (2011). Seeing with the eyes shut: Neural basis of enhanced imagery following ayahuasca ingestion. Human Brain Mapping, 33(11), 2550-2560. http://dx.doi.org/10.1002/hbm.21381
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Bringing Ayahuasca to the Clinical Research Laboratory

September 7, 2011 / Ayahuasca, Neuroscience, Other subjects, Papers, Psychiatry, Psychopharmacology, Publications / By / ,

Abstract

Since the winter of 1999, the authors and their research team have been conducting clinical studies involving the administration of ayahuasca to healthy volunteers. The rationale for conducting this kind of research is twofold. First, the growing interest of many individuals for traditional indigenous practices involving the ingestion of natural psychotropic drugs such as ayahuasca demands the systematic study of their pharmacological profiles in the target species, i.e., human beings. The complex nature of ayahuasca brews combining a large number of pharmacologically active compounds requires that research be carried out to establish the safety and overall pharmacological profile of these products. Second, the authors believe that the study of psychedelics in general calls for renewed attention. Although the molecular and electrophysiological level effects of these drugs are relatively well characterized, current knowledge of the mechanisms by which these compounds modify the higher order cognitive processes in the way they do is still incomplete, to say the least. The present article describes the development of the research effort carried out at the Autonomous University of Barcelona, commenting on several methodological aspects and reviewing the basic clinical findings. It also describes the research currently underway in our laboratory, and briefly comments on two new studies we plan to undertake in order to further our knowledge of the pharmacology of ayahuasca.

Riba, J., & Barbanoj, M. J. (2005). Bringing ayahuasca to the clinical research laboratory. Journal of Psychoactive Drugs, 37(2), 219-230. 10.1080/02791072.2005.10399804
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In Vivo Imaging of Cerebral Serotonin Transporter and Serotonin 2A Receptor Binding in MDMA and Hallucinogen Users

June 6, 2011 / Ayahuasca, Cacti / Mescaline, DMT, LSD, MDMA, Mushrooms / Psilocybin, Neuroscience, Other subjects, Papers, Psychology, Psychopharmacology, Publications, Salvia / Salvinorin A / By / , , , , , ,

Abstract

Context:
Both hallucinogens and 3,4-methylenedioxy-methamphetamine (MDMA or “ecstasy”) have direct agonistic effects on postsynaptic serotonin 2A receptors, the key site for hallucinogenic actions. In addition, MDMA is a potent releaser and reuptake inhibitor of presynaptic serotonin.

Objective:
To assess the differential effects of MDMA and hallucinogen use on cerebral serotonin transporter (SERT) and serotonin2Areceptor binding.

Design:
A positron emission tomography study of 24 young adult drug users and 21 nonusing control partici-pants performed with carbon 11 (11C)–labeled 3-amino-4-[2-[(di(methyl)amino)methyl]phenyl]sulfanylbenzo-nitrile (DASB) and fluorine 18 (18F)–labeled altanserin, respectively. Scans were performed in the user group after a minimum drug abstinence period of 11 days, and the group was subdivided into hallucinogen-preferring users (n = 10) and MDMA-preferring users (n = 14).

Participants:
Twenty-four young adult users of MDMA and/or hallucinogenic drugs and 21 nonusing controls.

Main Outcome Measures:
In vivo cerebral SERT and serotonin 2A receptor binding.

Results:
Compared with nonusers, MDMA-preferring users showed significant decreases in SERT nondisplaceable binding potential (neocortex, −56%; pallidostriatum, −19%; and amygdala, −32%); no significant changes were seen in hallucinogen-preferring users. Both cortical and pallidostriatal SERT nondisplaceable binding potential was negatively correlated with the number of life-time MDMA exposures, and the time of abstinence from MDMA was positively correlated with subcortical, but not cortical, SERT binding. A small decrease in neocortical serotonin 2A receptor binding in the serotonin 2A receptor agonist users (both user groups) was also detected.

Conclusions
We found evidence that MDMA but not hallucinogen use is associated with changes in the cerebral presynaptic serotonergic transmitter system. Because hallucinogenic drugs primarily have serotonin 2A receptor agonistic actions, we conclude that the negative association between MDMA use and cerebral SERT binding is mediated through a direct presynaptic MDMA effect rather than by the serotonin 2A agonistic effects of MDMA. Our cross-sectional data suggest that subcortical, but not cortical, recovery of SERT binding might take place after several months of MDMA abstinence.

Erritzoe, D., Frokjaer, V. G., Holst, K. K., Christoffersen, M., Johansen, S. S., Svarer, C., … Knudsen, G. M. (2011). In Vivo Imaging of Cerebral Serotonin Transporter and Serotonin 2A Receptor Binding in 3,4-Methylenedioxymethamphetamine (MDMA or “Ecstasy”) and Hallucinogen Users. Archives of General Psychiatry, 68(6), 562-576. http://dx.doi.org/10.1001/archgenpsychiatry.2011.56
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The 5-HT2A/1A Agonist Psilocybin Disrupts Modal Object Completion Associated with Visual Hallucinations

March 1, 2011 / Mushrooms / Psilocybin, Neuroscience, Other subjects, Papers, Psychology, Psychopharmacology, Publications / By / , , , ,

Abstract

Background: Recent findings suggest that the serotonergic system and particularly the 5-HT2A/1A receptors are implicated in visual processing and possibly the pathophysiology of visual disturbances including hallucinations in schizophrenia and Parkinson’s disease.

Methods: To investigate the role of 5-HT2A/1A receptors in visual processing the effect of the hallucinogenic 5-HT2A/1A agonist psilocybin (125 and 250 μg/kg vs. placebo) on the spatiotemporal dynamics of modal object completion was assessed in normal volunteers (n = 17) using visual evoked potential recordings in conjunction with topographic-mapping and source analysis. These effects were then considered in relation to the subjective intensity of psilocybin-induced visual hallucinations quantified by psychometric measurement.

Results: Psilocybin dose-dependently decreased the N170 and, in contrast, slightly enhanced the P1 component selectively over occipital electrode sites. The decrease of the N170 was most apparent during the processing of incomplete object figures. Moreover, during the time period of the N170, the overall reduction of the activation in the right extrastriate and posterior parietal areas correlated positively with the intensity of visual hallucinations.

Conclusions: These results suggest a central role of the 5-HT2A/1A-receptors in the modulation of visual processing. Specifically, a reduced N170 component was identified as potentially reflecting a key process of 5-HT2A/1A receptor–mediated visual hallucinations and aberrant modal object completion potential.

Kometer, M., Cahn, B. R., Andel, D., Carter, O. L., & Vollenweider, F. X. (2011). The 5-HT2A/1A Agonist Psilocybin Disrupts Modal Object Completion Associated with Visual Hallucinations. Biological Psychiatry, 69, 399–406. http://dx.doi.org/10.1016/j.biopsych.2010.10.002
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Residual neurocognitive features of long-term ecstasy users with minimal exposure to other drugs

February 15, 2011 / MDMA, Neuroscience, Other subjects, Papers, Psychology, Psychopharmacology, Publications, Safety, Toxicology / By / , , , , ,

Abstract

Aims: In field studies assessing cognitive function in illicit ecstasy users, there are several frequent confounding factors that might plausibly bias the findings toward an overestimate of ecstasy-induced neurocognitive toxicity. We designed an investigation seeking to minimize these possible sources of bias.

Design: We compared illicit ecstasy users and non-users while (1) excluding individuals with significant life-time exposure to other illicit drugs or alcohol; (2) requiring that all participants be members of the ‘rave’ subculture; and (3) testing all participants with breath, urine and hair samples at the time of evaluation to exclude possible surreptitious substance use. We compared groups with adjustment for age, gender, race/ethnicity, family-of-origin variables and childhood history of conduct disorder and attention deficit hyperactivity disorder. We provide significance levels without correction for multiple comparisons.
Setting: Field study.
Participants: Fifty-two illicit ecstasy users and 59 non-users, aged 18–45 years.
Measurements: Battery of 15 neuropsychological tests tapping a range of cognitive functions.
Findings: We found little evidence of decreased cognitive performance in ecstasy users, save for poorer strategic self-regulation, possibly reflecting increased impulsivity. However, this finding might have reflected a pre-morbid attribute of ecstasy users, rather than a residual neurotoxic effect of the drug. Conclusions In a study designed to minimize limitations found in many prior investigations, we failed to demonstrate marked residual cognitive effects in ecstasy users. This finding contrasts with many previous findings—including our own—and emphasizes the need for continued caution in interpreting field studies of cognitive function in illicit ecstasy users.
Halpern, J. H., Sherwood, A. R., Hudson, J. I., Gruber, S. Kozin, D., & Pope Jr., H. G. (2011). “Residual neurocognitive features of long-term ecstasy users with minimal exposure to other drugs. Addiction, 106(4), 777-786. http://dx.doi.org/10.1111/j.1360-0443.2010.03252.x
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Multiple receptors contribute to the behavioral effects of indoleamine hallucinogens

January 20, 2011 / Ayahuasca, Cacti / Mescaline, DMT, LSD, Mushrooms / Psilocybin, Neuroscience, Other subjects, Other substances, Papers, Psychiatry, Psychology, Publications / By / ,

Abstract

Serotonergic hallucinogens produce profound changes in perception, mood, and cognition. These drugs include phenylalkylamines such as mescaline and 2,5-dimethoxy-4-methylamphetamine (DOM), and indoleamines such as (+)-lysergic acid diethylamide (LSD) and psilocybin. Despite their differences in chemical structure, the two classes of hallucinogens produce remarkably similar subjective effects in humans, and induce cross-tolerance. The phenylalkylamine hallucinogens are selective 5-HT(2) receptor agonists, whereas the indoleamines are relatively non-selective for serotonin (5-HT) receptors. There is extensive evidence, from both animal and human studies, that the characteristic effects of hallucinogens are mediated by interactions with the 5-HT(2A) receptor. Nevertheless, there is also evidence that interactions with other receptor sites contribute to the psychopharmacological and behavioral effects of the indoleamine hallucinogens. This article reviews the evidence demonstrating that the effects of indoleamine hallucinogens in a variety of animal behavioral paradigms are mediated by both 5-HT(2) and non-5-HT(2) receptors.

Halberstadt, A. L., & Geyer, M.A. (2011). Multiple receptors contribute to the behavioral effects of indoleamine hallucinogens. Neuropharmacology, 61(3), 364-381. http://dx.doi.org/10.1016/j.neuropharm.2011.01.017
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Psychobiology of Drug-Induced Religious Experience: From the Brain 'Locus of Religion' to Cognitive Unbinding

November 13, 2010 / Ayahuasca, LSD, Mushrooms / Psilocybin, Mystical experiences, Neuroscience, Papers, Psychology, Publications, Religious studies, Spirituality / By / ,

Abstract

The recent interest in the psychopharmacological underpinnings of religious experiences has led to both the laboratory characterizations of drug-induced mystical events and psychobiological models of religious experiences rooted in evolution and fitness. Our examination of this literature suggests that these theories may be congruent only within more modern religious and cultural settings and are not generalizable to all historical beliefs, as would be expected from an evolutionarily conserved biological mechanism. The strong influence of culture on the subjective effects of drugs as well as religious thoughts argues against the concept of a common pathway in the brain uniquely responsible for these experiences. Rather, the role of personal beliefs, expectations and experiences may interject bias into the interpretation of psychoactive drug action as a reflection of biologically based religious thought. Thus, psychobiological research proposing specific brain mechanisms should consider anthropological and historical data to address alternative explanations to the “fitness” of religious thought. A psychobiological model of the religious experience based on the concept of cognitive unbinding seems to accommodate these data better than that of a specific brain locus of religion.

Nencini, P., & Grant, G. A. (2010). Psychobiology of Drug-Induced Religious Experience: From the Brain ‘Locus of Religion’ to Cognitive Unbinding. Substance Use & Misuse, 45(13), 2130–2151. http://dx.doi.org/10.3109/10826081003713803
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Glutamatergic Model Psychoses: Prediction Error, Learning, and Inference

September 22, 2010 / Ketamine, Neuroscience, Papers, Psychiatry, Psychology, Psychopharmacology, Psychosis, Publications / By / , , ,

Abstract

Modulating glutamatergic neurotransmission induces alterations in conscious experience that mimic the symptoms of early psychotic illness. We review studies that use intravenous administration of ketamine, focusing on interindividual variability in the profundity of the ketamine experience. We will consider this individual variability within a hypothetical model of brain and cognitive function centered upon learning and inference. Within this model, the brains, neural systems, and even single neurons specify expectations about their inputs and responding to violations of those expectations with new learning that renders future inputs more predictable. We argue that ketamine temporarily deranges this ability by perturbing both the ways in which prior expectations are specified and the ways in which expectancy violations are signaled. We suggest that the former effect is predominantly mediated by NMDA blockade and the latter by augmented and inappropriate feedforward glutamatergic signaling. We suggest that the observed interindividual variability emerges from individual differences in neural circuits that normally underpin the learning and inference processes described. The exact source for that variability is uncertain, although it is likely to arise not only from genetic variation but also from subjects’ previous experiences and prior learning. Furthermore, we argue that chronic, unlike acute, NMDA blockade alters the specification of expectancies more profoundly and permanently. Scrutinizing individual differences in the effects of acute and chronic ketamine administration in the context of the Bayesian brain model may generate new insights about the symptoms of psychosis; their underlying cognitive processes and neurocircuitry.

Corlett, P. R., Honey, G. D., Krystal, J. H., & Fletcher, P. C. (2011). Glutamatergic Model Psychoses: Prediction Error, Learning, and Inference. Neuropsychopharmacology Reviews, 36, 294–315. http://dx.doi.org/10.1038/npp.2010.163
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Abnormal visual experiences in individuals with histories of hallucinogen use: A web-based questionnaire

September 21, 2010 / HPPD, LSD, Neuroscience, Other disciplines, Other subjects, Other substances, Papers, Publications / By / , , , ,

Abstract

Despite longstanding reports of prolonged or reoccurring perceptual changes in a subset of hallucinogen users, very little is known about Hallucinogen Persisting Perception Disorder and related visual abnormalities in hallucinogen users. We used an online questionnaire to document the symptoms and relationship to drug use of unusual visual phenomena in hallucinogen users. 16,192 individuals viewed the information sheet and 2679 were included in the study. Of these, 224 reported having unrelated diagnoses associated with unusual visual experiences and were excluded from main analyses. Most (60.6%) of the remaining 2455 participants reported having experienced drug-free visual experiences that resembled hallucinogen effects. Probability of experiencing constant or near-constant symptoms was predicted by greater past exposure to specific hallucinogens, including lysergic acid diethylamide (LSD). Although symptoms were common, few (104, or 4.2% of the sample) found them distressing or impairing enough to consider seeking treatment. Visual changes in hallucinogen users may be more common than previously suspected and are worthy of further study.

Baggott, M. J., Coyle, J. R., Erowid, E., Erowid, F., & Robertson, L. C. (2011). Abnormal visual experiences in individuals with histories of hallucinogen use: A web-based questionnaire. Drug and alcohol dependence, 114(1), 61-67. http://dx.doi.org/10.1016/j.drugalcdep.2010.09.006
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The non-hallucinogen 2-bromo-lysergic acid diethylamide as preventative treatment for cluster headache: An open, non-randomized case series

March 26, 2010 / Chemistry, Cluster headache, LSD, Medicine, Neuroscience, Other substances, Papers, Publications / By / , , ,

Introduction

Cluster headache (CH) is a stereotyped primary headache characterized by strictly unilateral severe orbital or periorbital pain and categorized as either episodic or chronic (1,2). Its prevalence is 0.1% (3). Oxygen and sumatriptan are the treatments of choice for individual attacks, whereas verapamil, lithium, corticosteroids and other neuromodulators can suppress attacks during cluster periods (1). All standard medication treatments may be ineffective. Surgical treatment may be an option for medication non-responders, including deep brain (4) or occipital nerve stimulation (5). However, serious complications from brain surgery, including death, can occur (6).

An Internet survey of 53 CH patients reported on claims that psilocybin is better at aborting acute attacks than either oxygen or sumatriptan and that LSD and psilocybin are both better at triggering and extending remission than standard drugs (7). However, due to hallucinogenicity and the absence of established medical indication, these drugs are criminalized and placed within the most restrictive Schedule I of the Controlled Substances Act, which sanctions only limited research use. Although the hallucinogenic properties of LSD and psilocybin are undesirable from both regulatory and patient safety perspectives, it was unclear to us at the outset whether a non-hallucinogenic analog could also provide meaningful relief to CH patients. To address the question of whether the CH relief associated with these two structurally diverse compounds is related to the mechanisms triggering intoxication, we decided to investigate the efficacy of a non-hallucinogenic analog of LSD. LSD’s hallucinogenic effects are completely lost when the double bond in the D ring is saturated and with substitution at R2 (e.g. by bromination in 2-bromo-LSD) (BOL-148) (8). BOL-148 has been studied in volunteers (up to 20 mg per os) (9) and in patients suffering from vascular headaches but not, apparently, in patients with CH (9,10). These past studies [fusion_builder_container hundred_percent=”yes” overflow=”visible”][fusion_builder_row][fusion_builder_column type=”1_1″ background_position=”left top” background_color=”” border_size=”” border_color=”” border_style=”solid” spacing=”yes” background_image=”” background_repeat=”no-repeat” padding=”” margin_top=”0px” margin_bottom=”0px” class=”” id=”” animation_type=”” animation_speed=”0.3″ animation_direction=”left” hide_on_mobile=”no” center_content=”no” min_height=”none”][…]

Karst, M., Halpern, J. H., Bernateck, M., & Passie, T. (2010). The non-hallucinogen 2-bromo-lysergic acid diethylamide as preventative treatment for cluster headache: An open, non-randomized case series. Cephalalgia, 30(9), 1140-1144. https://dx.doi.org/10.1177/0333102410363490
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