People on acid have visions. Literally.
For a study at Imperial College London, researchers took scans of participants’ brains while they were high on LSD. What they discovered was pretty far out: even while the subjects’ eyes were closed, the part of the brain used for sight remained active, meaning the participants were literally seeing things.
"We observed brain changes under LSD that suggested our volunteers were 'seeing with their eyes shut' - albeit they were seeing things from their imagination rather than from the outside world,” said Dr. Robin Carhart-Harris, who led the study.
But these weren’t just visions—at least, not in the traditional sense. As the subjects hallucinated, researchers saw parts of their brains light up that normally have nothing to do with sight. Their senses were becoming intertwined.
As Carhart-Harris explained, this means that when LSD users say they’ve experienced an altered state of consciousness, they really mean it.
“Normally our brain consists of independent networks that perform separate specialized functions, such as vision, movement and hearing,” he said. “However, under LSD the separateness of these networks breaks down and instead you see a more integrated or unified brain.”
Carhart-Harris said this may even explain the feeling of “ego dissolution” experienced by many LSD users. Instead of feeling like an individual with a specific set of senses, “the normal sense of self is broken down and replaced by a sense of reconnection with themselves, others and the natural world.”