Psilocybin desynchronizes brain networks

Summary & key facts

Researchers scanned the brains of healthy adults many times before, during, and after they took psilocybin to see how the drug changes brain activity. Psilocybin made different brain areas stop working together — especially a group called the default mode network that helps make our sense of self — and these changes were much larger than what they saw after methylphenidate. Some of the changes lasted for weeks (but went back to normal by about six months). Doing a simple perception task while on psilocybin reduced the brain changes, which fits with the idea that grounding people in the present can lessen the psychedelic effects. The authors say the lasting drop in connection between the front of the hippocampus and cortex could be one way psilocybin helps the brain become more changeable and might relate to its antidepressant effects, but this is a candidate idea that needs more testing.

Key facts:

• The study followed healthy adults with many brain scans: each person had 17 MRI visits before, during, and after taking drugs.
• Psilocybin caused about 3 times bigger immediate changes in brain network connections than methylphenidate, a stimulant used for comparison.
• The main effect was 'desynchronization,' meaning different brain areas became less in sync with each other across small and large scales.
• Desynchronization was strongest in the default mode network, a brain network linked to our sense of self, and this network is connected to the front (anterior) part of the hippocampus.
• Doing a perceptual task while people were on psilocybin reduced the amount of network change, supporting the idea that focusing on the outside world can ‘ground’ people under psychedelics.
• Some psilocybin effects lasted for weeks: the connection between the anterior hippocampus and cortex stayed lower for weeks but returned to normal by about six months.
• The authors describe the lasting drop in hippocampus–default mode network connectivity as a candidate brain mechanism for psilocybin’s ability to increase brain plasticity and possibly its antidepressant effects, but they do not claim this is proven.

Abstract

1 Summary The relationship between the acute effects of psychedelics and their persisting neurobiological and psychological effects is poorly understood. Here, we tracked brain changes with longitudinal precision functional mapping in healthy adults before, during, and for up to 3 weeks after oral psilocybin and methylphenidate (17 MRI visits per participant) and again 6+ months later. Psilocybin disrupted connectivity across cortical networks and subcortical structures, producing more than 3-fold greater acute changes in functional networks than methylphenidate. These changes were driven by desynchronization of brain activity across spatial scales (area, network, whole brain). Psilocybin-driven desynchronization was observed across association cortex but strongest in the default mode network (DMN), which is connected to the anterior hippocampus and thought to create our sense of self. Performing a perceptual task reduced psilocybin-induced network changes, suggesting a neurobiological basis for grounding , connecting with physical reality during psychedelic therapy. The acute brain effects of psilocybin are consistent with distortions of space-time and the self. Psilocybin induced persistent decrease in functional connectivity between the anterior hippocampus and cortex (and DMN in particular), lasting for weeks but normalizing after 6 months. Persistent suppression of hippocampal-DMN connectivity represents a candidate neuroanatomical and mechanistic correlate for psilocybin’s pro-plasticity and anti-depressant effects.

Topics

Chemical synthesis and alkaloids Neurotransmitter Receptor Influence on Behavior Psychedelics and Drug Studies

Categories

Clinical Psychology Psychology Social Sciences

Tags

Cognition Default mode network Hallucinogen Hippocampal formation Hippocampus Neuroscience Psilocybin Psychiatry Psychology

Substances

Psilocybin

Conditions & symptoms

Depression Feeling disconnected from others Sadness or low mood