PLoS One
2021
Alex Gamma, Thomas Metzinger
To develop a fine-grained phenomenological analysis of "pure awareness" experiences in meditators. An online survey in five language versions (German, English, French, Spanish, Italian) collected data from January to March 2020. A total of 92 questionnaire items on a visual analogue scale were submitted to exploratory and confirmatory factor analysis. Out of 3627 submitted responses, 1403 were...
PLoS One
February 17, 2012
Erich Studerus, Alex Gamma, Michael Kometer et al.
372 citations
Responses to hallucinogenic drugs, such as psilocybin, are believed to be critically dependent on the user's personality, current mood state, drug pre-experiences, expectancies, and social and environmental variables. However, little is known about the order of importance of these variables and their effect sizes in comparison to drug dose. Hence, this study investigated the effects of 24...
PLoS One
August 31, 2010
Erich Studerus, Alex Gamma, Franz X. Vollenweider
693 citations
The original scales of the OAV were shown to be multidimensional constructs. Eleven new lower order scales were constructed and demonstrated to have desirable psychometric properties. The new lower order scales are most likely better suited to assess drug induced ASC.
Journal of Psychopharmacology
September 1, 2005
Alex Gamma, Daniel Brandeis, Ruven Brandeis et al.
36 citations
Substance abuse and associated externalizing disorders are characterized by behavioural disinhibition and low impulse control, with reduced neural inhibition postulated to be the common underlying brain mechanism. The P3 component of event-related potentials (ERPs) is a widely used neurophysiological measure thought to reflect inhibitory brain processes, but as yet has not been assessed in...
Journal of Psychoactive Drugs
June 1, 2002
Franz X. Vollenweider, Matthias E. Liechti, Alex Gamma et al.
92 citations
Since the mid 1990s, MDMA has been increasingly used as a recreational drug called "Ecstasy" by young people in Europe and the United States. However, despite the widespread recreational use of Ecstasy, systematic data on the psychological and neurobiological effects of MDMA have been scant. To further our understanding of the mechanism of action of MDMA, the authors conducted several studies...
Human Brain Mapping
August 27, 2001
Edi Frei, Alex Gamma, Roberto D Pascual-Marqui et al.
175 citations
Abstract 3,4‐Methylenedioxymethamphetamine (MDMA; 'Ecstasy') is a psychostimulant drug producing heightened mood and facilitated social communication. In animal studies, MDMA effects are primarily mediated by serotonin (5‐HT), but also by dopamine (DA) and possibly noradrenaline (NA). In humans, however, the neurochemical and neurophysiological basis of acute MDMA effects remains unknown. The...
Psychopharmacology
March 5, 2001
Matthias E. Liechti, Alex Gamma, Franz X. Vollenweider
357 citations
Rationale3.4-Methylenedioxymethamphetamine (MDMA) mainly releases serotonin (5-HT) and is contained in the recreational drug Ecstasy. 5-HT is known to play an important role in mood and anxiety disorders, for which there is a female preponderance. To date, there are no systematic data on gender differences in the subjective effects of MDMA.ObjectivesThe present work analyzed the pooled data...
Journal of Clinical Psychopharmacology
February 1, 2001
Alex Gamma, Alfred Buck, Thomas Berthold et al.
84 citations
The long-term use of the serotonin-releaser and uptake-inhibitor 3,4-methylenedioxymethamphetamine (MDMA, "Ecstasy") has been associated with memory impairments and increased liability to depressive mood and anxiety attacks. It is unclear, however, whether these psychologic deviations are reflected in alterations of the underlying neurophysiologic substrate. The authors compared mood and...
Neuropsychopharmacology
May 1, 2000
Matthias E. Liechti, Christine Baumann, Alex Gamma et al.
3,4-Methylenedioxymethamphetamine (MDMA, “Ecstasy”) is a recreational drug that has been shown to release serotonin (5-HT) and dopamine (DA) in animals. The effect of MDMA on 5-HT release can be blocked by 5-HT uptake inhibitors such as citalopram, suggesting that MDMA interacts with the 5-HT uptake site. It is unknown whether this mechanism is also responsible for the psychological effects of...
Neuroreport
2000
Alex Gamma, Edi Frei, Dietrich Lehmann et al.
81 citations
Resting EEG during open and closed eyes and subsequent mood ratings were obtained from 15 Ecstasy users and 14 Ecstasy-naive controls. Absolute spectral power on the scalp, and the three-dimensional, intracerebral distribution of neuroelectric activity using low resolution brain electromagnetic tomography (LORETA) were computed. LORETA revealed global increases of theta, alpha 1 and beta 2/3...