Proceedings of the National Academy of Sciences
February 10, 2020
Lilian Kloft, Henry Otgaar, Arjan Blokland et al.
49 citations
Under the acute influence of THC, healthy volunteers showed a heightened tendency to form false memories compared to those given a placebo. In a double-blind, randomized trial, 64 participants completed memory tasks—including associative word lists and two virtual-reality misinformation scenarios—immediately while intoxicated and again one week later while sober. Intoxicated individuals exhibited a stronger false-recognition bias, especially when test items were weakly associated with studied material, and were more susceptible to misinformation in eyewitness and perpetrator scenarios. These false-memory effects were largely confined to the acute intoxication phase. The findings suggest that cannabis increases false-memory proneness and have practical implications for police interviews with suspects and eyewitnesses.
Psychopharmacology
June 27, 2019
Lilian Kloft, Henry Otgaar, Arjan Blokland et al.
19 citations
Cannabis intoxication and a history of regular cannabis use are linked to a more liberal response criterion in memory tasks, leading to higher false recognition of unrelated items. In a field study using the Deese/Roediger-McDermott (DRM) paradigm, regular cannabis consumers who were acutely intoxicated (n = 53), regular cannabis consumers who were sober (n = 50), and cannabis-naïve controls (n = 53) completed a memory test. False memory rates for critical lures did not statistically differ between groups, but both intoxicated and sober cannabis consumers falsely recognized more unrelated items than controls. Cannabis-naïve individuals showed higher memory accuracy compared with the intoxicated group.
NeuroImage
January 1, 2024
Pablo Mallaroni, Natasha L Mason, Lilian Kloft et al.
17 citations
Brain functional connectomes are unique fingerprints that persist across mental states, but their stability under altered states is unknown. After collective ayahuasca intake in 21 Santo Daime members, 7T fMRI showed reduced idiosyncrasy in static and dynamic functional connectivity, with a spatiotemporal reallocation of keypoint edges. Interindividual differences in higher-order connectivity motifs predicted perceptual drug effects, demonstrating that individualized connectivity markers can trace a subject's functional connectome across altered states of consciousness.
European Neuropsychopharmacology
February 3, 2022
Lilian Kloft, Henry Otgaar, Arjan Blokland et al.
17 citations
A double-blind, placebo-controlled trial with 60 healthy volunteers who had previously used MDMA examined the drug's effects on false memory. Participants received 75 mg of MDMA or a placebo and were tested using a word list task and two misinformation tasks involving a virtual reality crime scene. Memory was tested immediately and one week later. MDMA caused small impairments in true memory on the word list task at both time points. It increased false memory for related but non-critical lures immediately but decreased false memory for critical lures after a week. Episodic memory in the misinformation tasks was not consistently affected. The findings suggest no heightened vulnerability to external suggestion during MDMA intoxication.
Journal of Cognitive Neuroscience
January 1, 2023
Johannes G Ramaekers, Pablo Mallaroni, Lilian Kloft et al.
15 citations
In members of the Santo Daime church who regularly consume ayahuasca in a ritual setting, the brew's main psychoactive compound DMT drives feelings of oceanic boundlessness, visual restructuring, and ego dissolution, with these effects correlating with peak DMT concentration in the blood. However, measures of mental imagery—including visual perspective shifting, vividness of imagery, and associative thinking—did not noticeably differ between sober and ayahuasca conditions, though subjective cognitive flexibility was lower under ayahuasca. Two mental imagery measures (perspective shifts and cognitive flexibility) correlated with peak DMT levels. Long-term ayahuasca use may produce compensatory or neuroadaptive effects that dampen the acute impact on mental imagery.
Biomedicine & Pharmacotherapy
March 24, 2022
Francisco Madrid-Gambin, Àlex Gomez‐gómez, Arnau Busquets-García et al.
14 citations
Consumption of ayahuasca increases N-acyl-ethanolamine endocannabinoids, decreases 2-acyl-glycerol endocannabinoids, and alters several large-neutral amino acids (LNAAs) in human plasma. Most LNAAs were inversely associated with nine of eleven subscales of the 5-Dimension Altered States of Consciousness Rating Scale, except tryptophan, which was positively associated. Several endocannabinoids and hexosylceramides were directly associated with ayahuasca alkaloids. Enrichment analysis confirmed dysregulation in pathways involved in serotonin and dopamine synthesis. A crosstalk between circulating LNAAs and subjective effects is suggested, independent of alkaloid concentrations, providing insights into the metabolic fingerprint and mechanism of action underlying ayahuasca experiences.
Frontiers in Neuroscience
October 5, 2023
Pablo Mallaroni, Lilian Kloft, Natasha L. Mason et al.
8 citations
Repeated ayahuasca use is associated with a spatially distributed pattern of brain structural changes: sensorimotor areas become more distinct from surrounding regions while transmodal areas become less distinct. These changes correlate with the expression of genes for 5-HT2A receptors and other targets of ayahuasca, as well as with genes for transcription factors and immediate early genes previously linked to psychedelic-induced neuroplasticity in animal studies. The findings suggest that molecular mechanisms of psychedelic action may scale up to large-scale brain organization in living humans, potentially helping to explain behavioral differences in experienced users.
Journal of psychopharmacology (Oxford, England)
April 1, 2025
Manoj K Doss, Lilian Kloft, Natasha L Mason et al.
5 citations
In experienced users, ayahuasca acutely enhances recollection-based memory—the ability to recall specific details—without increasing false memories or affecting familiarity-based memory, a feeling of knowing. In an observational study of 24 Santo Daime members who had consumed ayahuasca over 500 times on average, participants completed a false memory task before and after taking a self-selected church dose. After ayahuasca, hit rates, memory accuracy, and recollection improved, while familiarity and false memory remained unchanged. The authors suggest that β-carboline activity in the brew may account for this recollection enhancement, which contrasts with past psychedelic research showing impaired recollection. Practice effects could not be ruled out, but multiple measures of false memory and metamemory did not improve across sessions.
bioRxiv (Cold Spring Harbor Laboratory)
October 11, 2022
Pablo Mallaroni, Natasha L. Mason, Lilian Kloft et al.
4 citations
preprint
Brain functional connectomes are unique and reliable identifiers of individuals, but it was unknown whether these 'fingerprints' persist during altered states of consciousness. Ayahuasca, a serotonergic psychedelic, disrupts functional connectivity. In a within-subject study using 7T fMRI, 21 members of the Santo Daime church were scanned after collective ayahuasca intake. Connectome fingerprinting revealed a shared functional space and a spatiotemporal reallocation of key edges. Differences in higher-order functional connectivity motifs predicted perceptual drug effects, showing that individualized connectivity markers can trace a subject's functional connectome across altered states.
Journal of Eating Disorders
December 4, 2025
Samuli Kangaslampi, Max Wolff, Manoj K. Doss et al.
1 citation
Psychedelics like psilocybin can trigger vivid memory-like experiences, but a recent case report claiming that two patients recovered dissociated traumatic memories during psilocybin treatment for anorexia nervosa may not have adequately considered alternative explanations. The cases do not necessarily show that psilocybin induces recovery of dissociated traumatic memories or could treat dissociative amnesia. The authors also caution against explicitly preparing patients for the emergence of forgotten material, as such suggestions warrant scrutiny.
Nature reviews. Neuroscience
July 1, 2021
Johannes G Ramaekers, Natasha L Mason, Lilian Kloft et al.
Acute cannabis intoxication can impair neurocognitive function, potentially leading to human error, injury, and psychological distress. However, the impairing effect varies among individuals and may not occur in all users. The neurocognitive response is driven by changes in mesocorticolimbic and salience network activity and can be exacerbated or mitigated by biological and pharmacological factors, product formulations, and frequency of use, and it can differ between recreational and therapeutic use. These determinants should be considered when defining cannabis impairment in legal contexts, prescribing cannabis therapeutically, and informing the public about safe and responsible use.