In a new study, scientists watched something strange happen inside the brain after a single dose of ketamine: the usual cognitive chain of command seemed to collapse.

Normally, sensory info comes in through lower-level brain networks, then gets filtered up to higher-level regions that run things like decision-making, introspection, and memory. But after ketamine, those boundaries got fuzzy. The brain’s high-level networks loosened control, and communication between regions became more direct.

“This hierarchy is kind of collapsed,” said Claudio Agnorelli, a neuroscientist at Imperial College London, where the study was conducted.

Ketamine Might Flatten the Brain’s Power Structure—and That Could Be Why It Helps With Depression

Researchers scanned the brains of 11 healthy men before and after ketamine using fMRI and PET imaging. Within a day, the brain’s default mode network (DMN)—the part linked to rumination and self-reflection—was playing a less dominant role. Meanwhile, areas responsible for bodily sensations and physical awareness were speaking up more. The brain started sharing power, in a way.

The DMN is often overactive in people with depression, keeping them stuck in cycles of negative thought. Flattening that structure may give other regions a chance to weigh in, especially ones tied to present-moment experience.

There was also a shift in synaptic activity. Researchers tracked levels of a protein called SV2A, which offers a glimpse into how connected brain cells are. One key region in the DMN, the posterior cingulate cortex, showed signs of increased connectivity after the drug. That means ketamine may not just change how the brain communicates, it might be helping it physically rewire.

Sam Mandel, CEO of Ketamine Clinics Los Angeles, called it “a fundamental reorganization of communication between networks” in an email to Live Science. He added that the effect might help patients “feel less trapped in rigid thought patterns.”

The study hasn’t been peer-reviewed yet, and it’s small—just 11 participants, all male, with no placebo group. Still, it builds a stronger bridge between what researchers have seen in animals and what’s actually happening in human brains.

What it’s really doing may be more radical than mood repair. It’s interrupting the usual flow of thought, letting the mind reorganize itself. Even if briefly.