Psychopharmacology
May 16, 2008
Karsten Heekeren, Jörg Daumann, Anna Neukirch et al.
158 citations
Both S-ketamine (an NMDA antagonist) and DMT (a 5HT2A agonist) reduced mismatch negativity (MMN) and impaired performance on a continuous performance test in healthy volunteers, but the effects differed. S-ketamine produced a more pronounced overall reduction in MMN and specifically affected the frontal source of MMN, while DMT did not. These distinct neurocognitive profiles suggest that the two classes of hallucinogens model different aspects of psychosis.
Frontiers in Physiology
February 11, 2020
Thomas A. W. Bolton, Diana Wotruba, Roman Buechler et al.
83 citations
Altered coordination between the default mode, central executive, and salience networks is linked to schizophrenia, but its role in earlier at-risk stages is unclear. Using dynamic functional connectivity and co-activation pattern analysis of resting-state fMRI, this study examined right anterior insula interactions in 19 individuals with subthreshold delusions and hallucinations (UHR), 28 with basic symptoms of self-experienced subclinical disturbances (BS), and 29 healthy controls. The right anterior insula governs transitions from the central executive to default mode network, which become dysfunctional before psychosis onset, especially when attenuated psychotic symptoms emerge.
Behavioural Pharmacology
November 1, 1998
Euphrosyne Gouzoulis‐mayfrank, Karsten Heekeren, B. Thelen et al.
79 citations
In a small double-blind, placebo-controlled study with 12 healthy subjects, the hallucinogen psilocybin increased prepulse inhibition (PPI) of the startle reflex, contrary to findings from animal models where hallucinogens disrupt PPI. Psilocybin had no clear effect on habituation of the startle reflex. These preliminary results suggest that the effects of hallucinogens on sensorimotor gating may differ between humans and animals, possibly due to differences in dose regimens or experimental parameters. Further research is needed to understand the relationship between hallucinogen-induced states and naturally occurring psychoses.
Neuropsychobiology
January 1, 2002
Euphrosyne Gouzoulis‐mayfrank, B. Thelen, Stefanie Maier et al.
69 citations
Psilocybin, a serotonergic hallucinogen, and the ecstasy-like drug MDE both slowed reaction times in a spatial attention task, while methamphetamine did not. Psilocybin caused especially slow responses to invalid cues at short intervals and a failure to inhibit responses to valid cues at long intervals for right visual field targets. These patterns resemble bilateral attention disengagement and a lateralized impairment of inhibition of return seen in acute psychotic states. The study used a double-blind design with 8 healthy volunteers per group. Limitations include small sample size, and the authors call for larger studies with other hallucinogens to explore links between visuospatial attention dysfunction and psychosis.
Journal of Psychopharmacology
May 1, 2007
Karsten Heekeren, Anna Neukirch, Jörg Daumann et al.
49 citations
Schizophrenia patients show reduced prepulse inhibition (PPI) of the startle reflex, but hallucinogen models of psychosis in healthy volunteers do not replicate this effect. In a double-blind crossover study with 15 healthy volunteers, the serotonergic hallucinogen DMT had no significant effect on PPI, while the NMDA antagonist S-ketamine increased PPI and decreased startle magnitude. Neither drug affected the attentional modulation of PPI. These results highlight differences between human hallucinogen models and both animal models and schizophrenia itself.
Pharmacopsychiatry
September 1, 2005
Euphrosyne Gouzoulis‐mayfrank, Anna Neukirch, Karsten Heekeren
2 citations
Two classes of hallucinogens—serotonergic agonists like DMT and NMDA antagonists like S-ketamine—produce distinct patterns of psychosis-like symptoms, rather than one being a universally better model of schizophrenia. In a double-blind crossover study with 15 healthy volunteers, DMT more strongly induced positive symptoms such as thought disorder and inappropriate affect, while S-ketamine more strongly induced negative symptoms, attention deficits, body perception disturbances, and catatonia-like motor phenomena. The findings suggest that each drug class models different aspects or subtypes of schizophrenia, not that the NMDA antagonist model is overall superior to the 5-HT2A agonist model.