Proceedings of the National Academy of Sciences
January 23, 2012
Alessandro Colasanti, Robin J. Tyacke, Robert Leech et al.
1,191 citations
Psychedelic drugs like psilocybin, found in magic mushrooms, produce profound changes in consciousness by decreasing activity and connectivity in key brain hub regions. Using functional MRI, researchers observed that psilocybin reduced cerebral blood flow and BOLD signal, especially in the thalamus, anterior cingulate cortex (ACC), and posterior cingulate cortex (PCC). Decreased activity in the ACC and medial prefrontal cortex (mPFC) predicted the intensity of subjective psychedelic effects. Psilocybin also reduced positive coupling between the mPFC and PCC. These findings suggest that psychedelics work by dampening the brain's connector hubs, leading to a state of unconstrained cognition.
Proc Natl Acad Sci U S A
April 11, 2016
Robin L. Carhart-Harris, Suresh Muthukumaraswamy, Leor Roseman et al.
887 citations
LSD produces marked changes in brain activity that correlate with its psychological effects. Increased blood flow in the visual cortex, decreased alpha power there, and an expanded functional connectivity profile of the primary visual cortex strongly correlated with visual hallucinations, suggesting that intrinsic brain activity influences visual processing more during the psychedelic state. Decreased connectivity between the parahippocampus and retrosplenial cortex correlated strongly with ego-dissolution and altered meaning, indicating this circuit's role in maintaining the self and processing meaning. Different imaging metrics showed strong relationships, allowing firmer inferences about their functional significance.
Sci Rep
October 13, 2017
Robin L Carhart-Harris, Leor Roseman, Mark Bolstridge et al.
590 citations
In patients with treatment-resistant depression, a single dose of psilocybin combined with psychological support reduced depressive symptoms and altered brain activity and connectivity. Functional MRI scans before and after treatment showed decreased blood flow in the temporal cortex, including the amygdala, and increased resting-state functional connectivity within the default-mode network. Reduced amygdala blood flow correlated with fewer depressive symptoms. Changes in connectivity between the ventromedial prefrontal cortex and inferior lateral parietal cortex, as well as between the parahippocampus and prefrontal cortex, predicted treatment response at five weeks. These brain changes differ from the drug's acute effects and suggest a 'reset' of neural circuits.
Curr Biol
April 13, 2016
Enzo Tagliazucchi, Leor Roseman, Mendel Kaelen et al.
531 citations
LSD, a potent serotonin-receptor agonist, increases global functional connectivity in the human brain, particularly in high-level association cortices and the thalamus, as shown by fMRI. These effects overlap with serotonin 2A receptor densities and correlate with subjective reports of ego dissolution. The drug also enhances communication between normally distinct brain networks, reducing the brain's modular and rich-club organization. This is the first modern human imaging study of LSD's acute effects on brain connectivity, demonstrating that LSD selectively expands global connectivity and blurs perceptual boundaries between self and environment.
Biological Psychiatry
January 10, 2014
Robin Carhart‐Harris, Kevin Murphy, Robert Leech et al.
182 citations
The medial temporal lobes (MTLs) are specifically involved in how MDMA works in the brain, though more research is needed to understand how the drug's characteristic subjective effects emerge from its modulation of spontaneous brain activity.
J Psychopharmacol
June 15, 2020
Anna Borissova, Bart Ferguson, Matthew B Wall et al.
37 citations
MDMA did not increase prosocial behavior in a controlled laboratory setting, despite raising blood levels of the drug and self-reported feelings of closeness and euphoria. In a double-blind, placebo-controlled experiment with 20 healthy volunteers, MDMA (100 mg) failed to significantly change task-based measures of empathy, trust, or cooperative behavior compared to placebo. Bayesian analyses supported the conclusion that MDMA and placebo had equivalent effects on empathy and cooperation. The drug also did not alter mood three days after administration. These findings suggest that the acute prosocial effects of MDMA observed in naturalistic or therapeutic contexts may not replicate under controlled experimental conditions.
UNC Libraries
April 22, 2020
Peter J. Hellyer, Luke T. Williams, Ben Sessa et al.
1 citation
Lysergic acid diethylamide (LSD) in microgram doses produces profound, sometimes life-changing experiences and is a uniquely powerful psychoactive substance. In the first modern neuroimaging study of LSD, marked changes in brain blood flow, electrical activity, and network communication patterns were observed. These changes correlated strongly with the drug's hallucinatory and consciousness-altering properties. The findings have implications for understanding the neurobiology of consciousness and for potential applications of LSD in psychological research.