For the first time ever, scientists have visualized the effects of lysergic acid diethylamide (LSD) on the human brain, shedding light on the way that the psychedelic compound alters brain activity.
Working with the Beckley Foundation, the Imperial College London team examined 20 healthy volunteers that received either a placebo or 75 micrograms of LSD.
After administration of either substance, they used numerous brain scanning techniques, including functional magnetic resonance imaging (fMRI) and magnetoencephalography (MEG), to create visuals of the specific regions of the brain that LSD acts on.
The study revealed what happens when people hallucinate under the influence of LSD. While normally, information from our eyes is processed in the visual cortex - a region of the brain located at the back of the head - the volunteers who took LSD showed activity in various additional areas during visual processing.
"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 Robin Carhart-Harris, the Imperial College researcher who led the study. "We saw that many more areas of the brain than normal were contributing to visual processing under LSD - even though the volunteers' eyes were closed. Furthermore, the size of this effect correlated with volunteers' ratings of complex, dreamlike visions. "
In addition to revealing the neural mechanisms behind visual processing under the influence of LSD, the team also revealed those responsible for the change in consciousness that people report when under the influence of the drug.
"Normally our brain consists of independent networks that perform separate specialized functions, such as vision, movement and hearing - as well as more complex things like attention," Carhart-Harris said. "However, under LSD the separateness of these networks breaks down and instead you see a more integrated or unified brain."
"In many ways, the brain in the LSD state resembles the state our brains were in when we were infants: free and unconstrained," he added. "This also makes sense when we consider the hyper-emotional and imaginative nature of an infant's mind."
Future research can use the breakthrough findings to reveal the potential ways that LSD can help scientists better understand the human brain and consciousness.
"We are finally unveiling the brain mechanisms underlying the potential of LSD, not only to heal, but also to deepen our understanding of consciousness itself," said Amanda Feilding, director of the Beckley Foundation.
The findings were published in the April 11 issue of the Proceedings of the National Academy of Sciences.
