LSD in the Human Brain: How it Changes Consciousness by Reorganizing Networks

What happens to a person's brain when they take LSD? While scientists have long known that it causes changes in consciousness, including ego-dissolution, researchers haven't understood how these pharmacological effects can translate into such a profound effect on consciousness. Now, they may have an answer.

In this latest study, the researchers did sequential brain scans of 20 healthy volunteers over 6 hours, using functional magnetic resonance imaging (fMRI), which maps brain activity by detecting changes in blood flow, and magnetoencephalography (MEG).

So what did they find? The researchers discovered that LSD led to a more chaotic brain state that's not entirely dissimilar to what is seen in the prodromal phase of psychosis. Specifically, neurons that were supposed to fire together within a network fell out of synchrony, while networks that are normally distinct started to overlap in their connectivity patterns.

The researchers also found increases in blood flow in the visual cortex at the back of the brain, which may explain the visual hallucinations and distortions so common in LSD intoxication. The scientists also found a change in natural brain oscillations, specifically a decrease in alpha waves across the brain. These were highly correlated to visual hallucinations, suggesting that under the influence of LSD, the visual system is tethered more to the internal than to the external world.

"With better assessment tools available today than in the 1950s and 1960s, it may be possible to evaluate potential uses of LSD as a treatment for addiction and other disorders, such as treatment-resistant depression-which we are currently investigating with a similar drug to LSD," said Robin Carhart-Harris, one of the researchers, in a news release.

The findings reveal a bit more about a useful human model of psychosis, as it leads to changes in brain network behavior that shows overlaps with the early phase of psychosis.

The findings are published in the journal Neuropsychopharmacology.

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