image: Serrgey75/Shutterstock A new paper in Nature Communications , covered by Ian Sample at the Guardian , claims a single 25mg dose may leave behind anatomical changes in the wiring itself, still visible 30 days on. Researchers at UC San Francisco and Imperial College London recruited 28 psychedelic-naive adults and gave each of them a token 1mg primer, then a full 25mg session a month later. They scanned every subject with diffusion tensor imaging, a technique that tracks how water moves along nerve bundles and infers their structural integrity. EEG during the 25mg session showed the expected entropy spike within an hour: the brain was processing more diverse signals at once. A month after the trip, DTI revealed reduced water flow along the bundles linking the prefrontal cortex to midbrain regions — a signature the authors interpreted as either fiber pruning or the growth of fresh, unmyelinated axons.…