How do psychedelics actually reshape brain activity? A 2026 systematic review of 49 electrophysiology studies

Bottom line: Psychedelics may reshape brain activity by altering neural timing and coordination rather than simply increasing volume, as suggested by a 2026 review of 49 electrophysiology studies.

In a quiet lab, a researcher watches a brainwave pattern flicker like a neon sign. The question: how can a tiny molecule create such a profound shift in perception? A new systematic review of 49 electrophysiology studies, published in Neuroscience & Biobehavioral Reviews in 2026, suggests the answer isn’t about volume. It’s about coordination.

The honest answer is no. Psychedelics don’t just increase brain activity; they reorganize it. And this reorganization may explain why people report vivid, immersive experiences even as fMRI scans show reduced overall brain activity.

The review, led by Hidalgo Jimenez, Kaup, and Aru, challenges the standard theory that psychedelics simply amplify neural firing. Instead, they act more like conductors than volume knobs, orchestrating a shift in timing and communication rather than boosting everything uniformly.

The Conductor, Not the Volume Knob

For years, the prevailing view has been that psychedelics like psilocybin or LSD increase brain activity by making neurons fire more frequently. This idea was supported by early fMRI studies that showed heightened activation in certain brain regions during psychedelic states. But the new review flips this narrative. It argues that the real change isn’t in the volume of activity—it’s in the timing and coordination of neural firing.

The review compiles data from 49 electrophysiology studies, many of which use techniques like electroencephalography (EEG) and intracranial recordings to measure the brain’s electrical activity in real time. What they found is striking: certain neurons, particularly layer 5 pyramidal neurons, often fire less under the influence of psychedelics. This contradicts the long-held belief that these neurons are the primary drivers of increased brain activity during such states.

Instead of firing more, these neurons exhibit altered dendritic processing and changes in calcium signaling. This suggests that the brain isn’t simply turning up the volume—it’s reconfiguring the way information is processed. The result is a shift in communication patterns, not a uniform increase in activity.

Glutamate and the Neighbors That Don’t Respond

One of the most intriguing findings from the review is the role of glutamate, the brain’s primary excitatory neurotransmitter. While glutamate release increases under psychedelics, the neighboring neurons that typically respond to it become less sensitive. This creates a paradox: the brain is releasing more of a signal, but the recipients are less responsive. The outcome is a reshaping of neural communication rather than a simple amplification.

This phenomenon could explain why fMRI scans often show reduced overall brain activity during psychedelic states. The reduction isn’t because the brain is quieter—it’s because the timing and coordination of firing have changed. The same neurons are still active, but they’re firing in a different rhythm, creating a new kind of neural harmony.

This finding aligns with two prominent theories in consciousness research: the Integrated Information Theory (IIT) and the Entropic Brain Hypothesis. IIT posits that consciousness arises from the integration of information across different brain regions, and the shift in neural coordination during psychedelic states may enhance this integration. The Entropic Brain Hypothesis, on the other hand, suggests that psychedelics reduce the brain’s entropy, or disorder, by promoting more coherent and synchronized activity. Both theories point to a shift in the brain’s internal dynamics rather than a simple increase in activity.

The Mystery of Timing

One of the most fascinating aspects of the review is its emphasis on timing. The idea that psychedelics don’t just increase the volume of neural activity but also alter the timing of firing is a radical departure from previous assumptions. This shift in timing may be what allows for the rich, immersive experiences people report during psychedelic states.

The review points to a potential mechanism: layer 5 pyramidal neurons, which are crucial for communication between different brain regions, may be modulating their firing patterns in response to psychedelics. This modulation could be what allows for the integration of information across the brain, creating a more unified and coherent experience.

But the exact nature of this timing shift remains unclear. While the review provides strong evidence that timing is a key factor, it doesn’t fully explain how or why this shift occurs. This is one of the open questions that the study highlights.

Frequently Asked Questions

Q: Does this mean psychedelics don’t increase brain activity at all?
A: No. The review doesn’t suggest that brain activity decreases. Instead, it argues that the activity is reorganized. Certain neurons may fire less, but others may fire in new, coordinated patterns.

Q: What role do layer 5 pyramidal neurons play?
A: Layer 5 pyramidal neurons are thought to be key in integrating information across different brain regions. The review suggests that these neurons may be modulating their firing patterns in response to psychedelics, which could explain the shift in neural communication.

Q: How does this relate to fMRI findings showing reduced brain activity?
A: The review suggests that the reduced activity seen in fMRI scans may not reflect a decrease in overall activity, but rather a shift in the timing and coordination of firing. The same neurons are still active, but they’re firing in a different rhythm.

Q: What theories does the review support?
A: The review aligns with both the Integrated Information Theory (IIT) and the Entropic Brain Hypothesis, suggesting that psychedelics may enhance information integration and reduce brain entropy.

Q: What are the limitations of the review?
A: The review does not provide evidence for the therapeutic potential of psychedelics. It focuses on the mechanism of action rather than clinical outcomes.

Sources

• ¶Hidalgo Jimenez, M., Kaup, A., & Aru, J. (2026). Neuroscience & Biobehavioral Reviews, 185, 106649. DOI: 10.1016/j.neubiorev.2026.106649

Educational Disclaimer

This article is for informational and educational purposes only. It is not medical advice, mental health advice, diagnosis, treatment guidance, or a recommendation to use any substance, supplement, therapy, or protocol.

We review publicly available research and explain what the evidence may suggest. Some studies may be early-stage, observational, animal-based, lab-based, theoretical, or incomplete. Always consult a qualified professional before making health-related decisions.

Researched and drafted by Spore, ShroomWire’s AI research assistant, and reviewed by the ShroomWire editorial team before publishing.

If you or someone you know is struggling, you are not alone. In the US, call or text 988 (Suicide & Crisis Lifeline). Elsewhere, contact your local emergency or crisis service.