Psychedelics restructure information in the human brain
Using a multivariate information decomposition framework on data from 80 participants, this study reveals that five different psychedelics restructure human brain function by reducing neural self-coupling, causing cortical populations to become more alike in their information processing without necessarily synchronizing, thereby offering a unified explanation for altered subjective experiences and therapeutic effects.
Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). This is an AI-generated explanation of a preprint that has not been peer-reviewed. It is not medical advice. Do not make health decisions based on this content. Read full disclaimer
For decades, scientists have watched the brain under the influence of psychedelic drugs and seen a familiar pattern: the distinct, separate regions of the mind seem to blur together. The prevailing story has been that these substances force the brain into a state of total unity, where information flows freely between every part, creating a single, integrated whole. This idea of "global integration" has become the standard explanation for both the vivid, expansive experiences people report and the potential for these drugs to treat mental health conditions. However, this story relies on a vague understanding of what "integration" actually means. Does it mean different brain areas are holding the same information? Does it mean they are passing information back and forth? Or does it mean they are combining their efforts to create something new? Without a precise way to measure these different possibilities, the scientific community has been looking at a complex picture through a foggy lens, unable to distinguish between different types of connection.
A team of researchers has now cleared that fog by applying a new mathematical lens to data from eighty healthy volunteers who took five different psychedelic substances: LSD, psilocybin, ketamine, DMT, and 5-MeO-DMT. Instead of simply asking if brain regions are connected, they broke down the flow of information into its most basic components, asking exactly how information is stored, copied, or transformed as it moves through time. Their findings overturn the simple narrative of total unity. They discovered that while these drugs do make different parts of the brain more similar to one another, they do not necessarily make them work together in a coordinated, collective way. In fact, the drugs often disrupt the brain's ability to hold onto unique, private information, forcing regions to mirror each other rather than collaborate. The result is a brain that is "alike, but not necessarily together."
To understand what the researchers found, one must first understand the tool they used. They employed a method called integrated information decomposition, which acts like a high-resolution microscope for data. Imagine trying to understand a conversation between two people. A standard measure might just tell you that they are speaking at the same time. This new method, however, can tell you if they are repeating the same words, if one is copying the other, if they are combining their thoughts to create a new idea, or if one is keeping a secret while the other speaks. The researchers applied this method to the electrical activity of the brain, tracking how information moved from one moment to the next across different brain regions. They looked for ten distinct ways information can behave, ranging from simple copying to complex, cooperative creation.
When they analyzed the data from the five drugs, a clear and surprising pattern emerged. The most consistent change was a loss of "preservation." In a normal brain, a specific region can hold onto a piece of information, keeping it unique to itself for a short time. Under the influence of psychedelics, this ability to hold private information collapses. The brain regions stop keeping their own unique data and instead become flooded with information that is identical to what their neighbors are holding. This creates a state where the brain is filled with redundant, repeated signals. It is as if the brain's internal radio stations, which usually broadcast different programs, suddenly switch to playing the exact same song on every frequency. This loss of unique storage explains why the brain's overall signal becomes more "complex" or diverse; without the anchor of stable, private information, the system becomes more chaotic and free to change.
However, the story is not the same for every drug. While LSD, psilocybin, and DMT generally increased this redundancy, making different brain areas look more alike, the drug 5-MeO-DMT did the opposite. It strengthened the brain's ability to keep information private and unique, while reducing the similarity between regions. This suggests that not all psychedelic experiences are built on the same neural foundation. Furthermore, the researchers found that the drugs did not significantly increase the kind of "cooperation" that would suggest the brain is building complex, collective structures. The idea that these drugs create a super-integrated brain where parts work together to form a higher whole was not supported by the data. Instead, the brain seemed to be in a state of constant, uncoordinated mirroring.
The researchers also built a simple computer model to test what causes these changes. They simulated a network of brain regions and tweaked the settings to see what would happen. They found that the entire chaotic effect could be explained by a single, simple change: reducing the "self-coupling" of the brain regions. In plain terms, this means the drugs weaken a brain region's ability to influence itself. When a region can no longer hold its own ground, it becomes highly susceptible to the signals coming from its neighbors, causing it to simply copy them. This single mechanism—losing the ability to be self-sufficient—was enough to recreate the messy, mirrored state seen in the human data. It suggests that the profound changes in consciousness caused by these drugs might stem from a very basic failure in how individual brain cells maintain their own identity.
These findings challenge the long-held belief that psychedelics work by unlocking a hidden, unified state of the brain. Instead, they suggest a more nuanced reality where the brain loses its internal boundaries. The regions become alike, echoing each other's signals, but they do not necessarily join forces to create something greater than the sum of their parts. This distinction is crucial for understanding how these drugs might help treat mental health conditions. If the therapeutic effect comes from breaking rigid, repetitive patterns of thought, then the mechanism might be this very loss of self-contained stability, allowing the brain to escape its usual loops. The study does not claim to have solved the mystery of consciousness, but it provides a much sharper definition of what is actually happening inside the mind when the walls between its parts come down. The psychedelic brain is not a choir singing in perfect harmony; it is a room where everyone is suddenly speaking the same words, but perhaps not listening to each other.
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