Neuroreport
December 1, 1998
Franz X. Vollenweider, M. F. I. Vollenweider-Scherpenhuyzen, Andreas Bäbler et al.
1,023 citations
The hallucinogen psilocybin induces a psychosis-like state in healthy people that resembles early schizophrenia. In human volunteers, these effects were blocked in a dose-dependent manner by the serotonin-2A antagonist ketanserin or the atypical antipsychotic risperidone, but were increased by the dopamine antagonist and typical antipsychotic haloperidol. This provides the first human evidence that psilocybin-induced psychosis results from serotonin-2A receptor activation, independent of dopamine stimulation. The findings suggest that serotonin-2A overactivity may play a role in schizophrenia and that blocking this receptor may contribute to antipsychotic benefits.
Archives of General Psychiatry
December 1, 2000
Daniel Umbricht, Liselotte Schmid, Rene Koller et al.
590 citations
In healthy volunteers, the N-methyl-D-aspartate receptor (NMDAR) antagonist ketamine significantly reduced the amplitude of mismatch negativity (MMN) brain responses to pitch and duration changes by 27% and 21%, respectively. Ketamine also impaired performance on a continuous performance test, decreasing hit rates and increasing specific context-dependent errors (BX errors), indicating a failure to form and use transient memory traces. These findings suggest that NMDARs are critically involved in generating MMN and that NMDAR dysfunction may underlie deficits in transient memory at different levels of information processing in schizophrenia.
Journal of Psychopharmacology
May 20, 2006
Marc Wittmann, Olivia Carter, Felix Hasler et al.
245 citations
Psilocybin impairs the ability to reproduce time intervals longer than 2.5 seconds, to synchronize movements to beats longer than 2 seconds, and slows preferred tapping rate. These objective timing deficits are accompanied by working-memory impairments and subjective changes including depersonalization and derealization. The findings indicate the serotonin system is selectively involved in processing durations longer than 2–3 seconds and in voluntary movement speed control. The disruption of longer intervals likely results from interactions with cognitive dimensions of temporal processing via 5-HT2A receptor stimulation.
Human Brain Mapping
August 27, 2001
Edi Frei, Alex Gamma, Roberto D. Pascual‐marqui et al.
175 citations
A single dose of MDMA (1.7 mg/kg) in 16 healthy, MDMA-naïve volunteers produced widespread decreases in slow and medium frequency brain activity and increases in fast frequency activity in the anterior temporal and posterior orbital cortex, as measured by scalp EEG and low resolution brain electromagnetic tomography (LORETA). These changes were accompanied by heightened mood, emotional arousal, and increased extraversion. The EEG pattern suggests that serotonin, noradrenaline, and, to a lesser degree, dopamine contribute to MDMA's effects on brain activity and possibly mood and behavior, indicating modulation of limbic orbitofrontal and anterotemporal structures involved in emotional processes.
Neuropsychopharmacology
January 26, 2005
Olivia Carter, John D. Pettigrew, Felix Hasler et al.
122 citations
Binocular rivalry, where each eye sees a different image and perception alternates between them, is influenced by psilocybin. In 12 healthy volunteers, both low (115 µg/kg) and high (250 µg/kg) doses of psilocybin significantly reduced the rate and rhythmicity of perceptual alternations 90 minutes after administration, compared to placebo. Over time, switch rates increased, with some exceeding pretest levels at 360 minutes, though mean phase duration did not significantly differ from placebo. Drug-induced changes in rivalry phase durations corresponded to altered states of consciousness measured by the 5D-ASC scale. The findings implicate serotonergic pathways and support a brainstem oscillator's role in perceptual rivalry and psychosis symptoms.
Neuroreport
January 1, 2000
Alex Gamma, Edi Frei, Dietrich Lehmann et al.
81 citations
People who regularly use Ecstasy show altered brain activity patterns, including increased theta, alpha, and beta power across the scalp, particularly with eyes open, as measured by EEG and brain tomography. They also report higher levels of state depressiveness, emotional excitability, and a trend toward increased state anxiety compared to non-users. These differences could stem from regular Ecstasy or other illicit drug use, or may have existed before drug use began.