Psychedelics temporarily alter cooperation between brain networks

There is a new scientific article in Nature Medicine appeared that shows how classical psychedelics temporarily alter the cooperation between large brain networks.

In it, we discuss:

The researchers conducted an international mega-analysis of 11 independent resting-state fMRI datasets from different countries. In doing so, they looked at the acute effects of psilocybin, LSD, DMT, ayahuasca and mescaline on functional connectivity in the brain. Functional connectivity here means that brain regions are temporarily more or less synchronously active with each other.

The main finding is that psychedelics mainly increase coupling between different brain networks. This is especially true for connections between higher association networks, such as the default mode network and frontoparietal network, and more sensory or motor networks, such as visual, somatomotor and attention networks.

This nuances the popular idea that psychedelics mainly “switch off” the default mode network or cause broad disintegration in the brain. According to this mega-analysis, the picture seems more nuanced: psychedelics temporarily put the brain into a different network state, where normally more separate systems start to communicate more strongly with each other.

Declines were also seen within some networks, especially within sensory and motor networks, but these effects were less broad and less robust than the increase in connections between networks. Among other things, the researchers used Bayesian models to better distinguish between clear patterns and effects that could be affected by small data sets or analytical methods.

Psilocybin and LSD showed very similar patterns. DMT seemed to have a stronger effect in this analysis, but that result is based on a small data set. Mescaline was partly similar to psilocybin and LSD. Ayahuasca differed more from the other psychedelics, but even for that the dataset was small, so firm conclusions should be interpreted with caution.

Importantly, this research is mainly about acute brain activity during the action of psychedelics. So it does not directly prove that these network changes are in themselves responsible for therapeutic effects. However, the article does help to better understand why psychedelic experiences are often accompanied by changes in perception, emotion, memory, meaning-making and perspective.

In one sentence, this article shows that psychedelics do not simply turn the brain “on” or “off”, but temporarily rearrange the cooperation between brain networks.