Yes, in a small placebo-controlled study of psychedelic-naive adults, a single high psilocybin session was linked to measurable brain changes during the acute experience and exploratory improvements in psychological measures one month later. See the report in Nature Communications for details.
Acute EEG effects included higher brain entropy, estimated with Lempel-Ziv complexity, and lower alpha activity about 1 to 2 hours after dosing. Greater acute entropy correlated with more psychological insight the next day, which in turn related to higher well-being at one month.
At one month, DTI suggested changes in prefrontal to subcortical white-matter pathways, while resting-state fMRI showed little sustained connectivity change. Lower network modularity was associated with higher well-being.
These findings are exploratory, the sample was small, and participants were healthy volunteers, so this does not show a treatment effect. I cannot independently verify the full dataset. Replication and larger studies are needed.
Hope this clarifies.