Ian Sample in The Guardian:
The images, taken from volunteers who agreed to take a trip in the name of science, have given researchers an unprecedented insight into the neural basis for effects produced by one of the most powerful drugs ever created.
A dose of the psychedelic substance – injected rather than dropped – unleashed a wave of changes that altered activity and connectivity across the brain. This has led scientists to new theories of visual hallucinations and the sense of oneness with the universe some users report.
The brain scans revealed that trippers experienced images through information drawn from many parts of their brains, and not just the visual cortex at the back of the head that normally processes visual information. Under the drug, regions once segregated spoke to one another.
Further images showed that other brain regions that usually form a network became more separated in a change that accompanied users’ feelings of oneness with the world, a loss of personal identity called “ego dissolution”.
More here.