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In recent years, there has been a lot of attention for what psychedelics “Doing things to the brain.” In popular explanations, a simplistic image often emerges: as if psychedelics primarily “switch off” a single network, such as the default mode network, or “disintegrate” the brain in a general sense. A new scientific article, published in Nature Medicine and summarized in an accessible source on Tripforum, reveals a more nuanced and technically interesting picture: classic psychedelics appear to temporarily reorganize the cooperation between major brain networks.

In this article, we explain exactly what was investigated using resting-state fMRI, what “functional connectivity” means, what the key findings are, and what you can and cannot conclude regarding therapy, trauma, and safety. We distinguish between research results, interpretations, and practical significance. This is not medical advice.

What was investigated and why is this special?

The researchers conducted an international mega-analysis based on 11 independent resting-state fMRI datasets from various countries. Instead of one small study with one substance and one analysis method, they combined multiple datasets to obtain a more reliable picture of recurring patterns across different psychedelics.

The substances in the analysis were classic psychedelics: psilocybin, LSD, DMT, ayahuasca and mescaline. The acute effects, therefore looking at changes during the operating period, not at long-term effects weeks or months later.

The central concept is functional connectivity. In this context, it means: to what extent are brain regions or networks temporarily synchronously active (fluctuating together to a greater or lesser extent) during rest in the scanner. It is therefore not about “hard wiring” or structural connections, but about a measurable correlation in activity patterns.

Resting-state fMRI in plain language

In resting-state fMRI, a person lies still in a scanner and is usually instructed to rest, without a specific task. The scanner indirectly measures brain activity via changes in blood flow (the BOLD signal). Researchers then look at which areas or networks move up and down together over time. If two networks “move along” more, this is interpreted as a stronger functional coupling.

It is important to know that resting-state fMRI cannot “read” thoughts, nor can it pinpoint the exact origin of an experience. It is a method to describe patterns of cooperation within the brain, not to directly prove personal meaning or psychological processes.

The key finding: more coupling between normally separated networks

The most important outcome of this mega-analysis is that psychedelics primarily the increase coupling between different major brain networks. This applied in particular to connections between:

1) Higher association networks (also known as transmodal networks), such as the default mode network and the frontoparietal network.

2) More sensory and motor networks (unimodal networks), such as visual, somatomotor and attention networks.

In simpler words: systems that more often operate “separately” in daily functioning appear temporarily under the influence of psychedelics. to communicate more with each other. This aligns with many described phenomena of psychedelic experiences, such as changes in perception, a stronger emotional or physical component, shifts in meaning-making, and the experience of new perspectives. At the same time, the latter is an interpretation: the fMRI data primarily show that the network state changes, not exactly which experience is associated with it.

Nuance: not simply turning the default mode network “off”

An important point is that this mega-analysis nuances the popular idea that psychedelics primarily “switch off” the default mode network or that there is mainly a broad decrease in cohesion. The researchers did see declines within some networks, especially within sensory and motor networks, but those effects were less wide and less robust than the increase in connections between networks.

That does not mean that previous studies are “wrong.” It may involve differences in samples, dosage, setting, analysis methods, or statistical choices. That is precisely why a mega-analysis is interesting: it can help find patterns that are less dependent on one specific dataset.

Differences between agents: similarities and uncertainties

In the analysis, we showed psilocybin and LSD see strongly similar patterns. DMT appeared to have a stronger effect, but that result is based on a smaller dataset, so caution is needed. Mescaline resembled psilocybin and LSD in part. Ayahuasca deviated more from the other psychedelics, but here too the dataset was smaller, making firm conclusions more difficult.

These types of differences are relevant, but it is important not to over-interpret them. In small datasets, an effect may appear larger due to chance, selection effects, or methodological variation. The researchers used Bayesian models, among others, to better distinguish which patterns are likely robust and which might be influenced by noise or methodological differences.

What do subcortical areas contribute?

In addition to the large networks in the cerebral cortex, changes were also observed in the coupling of subcortical areas, such as caudatus, putamen, thalamus and the cerebellum, with sensorimotor networks. These structures are involved in, among other things, switching functions, signal integration, and coordination of information processing.

It is tempting to draw direct psychological conclusions from this, but caution is warranted. fMRI shows correlations and network patterns, not direct causality. However, it does support the idea that psychedelics do not merely influence “a few areas,” but temporarily affect a broader network organization.

What does this mean for therapy and trauma?

Many people are interested in psychedelics due to potential therapeutic applications, for example in relation to trauma. This study primarily helps with the understanding acute brain states during the action of psychedelics. It does not prove that the observed network changes are in themselves responsible for therapeutic outcomes.

Therapeutic change is usually an interplay of factors: preparation, setting, guidance, psychological processes, subsequent integration, an individual's life context, and sometimes comorbid complaints. Brain imaging can support hypotheses, but it is rarely an “explanation in a single graph”.

For those wishing to delve into the relationship between MDMA, trauma, and therapy, it is useful to distinguish between research into MDMA-assisted therapy and research into classic psychedelics. Pharmacologically, MDMA is not a classic psychedelic, and effects on experience and possible mechanisms of action differ. More background on the theme of trauma in relation to MDMA can be found on the page. MDMA and trauma.

It is also important to mention that MDMA sessions are currently only conducted within scientific research or in practice via harm reduction. can be discussed. This means that in non-research contexts, the emphasis lies on risk reduction, screening where possible, preparation, setting, and integration, and not on medical claims or treatment guarantees.

Safety and harm reduction: why nuance remains necessary

Neuroimaging research can help understand effects, but says little in itself about safety at the individual level. There are significant uncertainties: dose, combination with other substances, sleep deprivation, physical strain, psychological vulnerability, medication use, and the (social) setting can strongly influence the risk profile.

Harm reduction does not operate on the assumption that “more knowledge about the brain” automatically means it is safe. It involves a realistic assessment of risks, avoiding dangerous combinations, recognizing signs of overload, and organizing a setting that allows for preparation and integration. This article can help temper the hype: psychedelics do not simply turn the brain on or off, but temporarily place it in a different network state. That is interesting, but no guarantee of a positive or therapeutic outcome.

Source and further information

The above summary is based on the source page: Psychedelics temporarily alter the cooperation between brain networks.. The value of this type of mega-analysis is that they show a more likely “average pattern” across multiple studies, while simultaneously demonstrating the limits of what we already know for certain.

Conclusion

This mega-analysis of resting-state fMRI shows that classic psychedelics do not simply disrupt the brain or disable a single network, but temporarily rearrange the cooperation between major brain networks. The increased coupling between higher association networks and sensorimotor networks stands out in particular. At the same time, caution remains necessary: this concerns acute effects, not evidence for therapeutic mechanisms, and some substance-specific conclusions are uncertain due to smaller datasets.

Anyone considering guided sessions would do well to keep the distinction between science, anecdotal evidence, and practical harm reduction clear. If you wish to explore the available options and the questions relevant during an intake, you can find information or register via register for an MDMA session, bearing in mind that MDMA sessions can currently only be discussed within the context of scientific research or through a harm reduction practice.