Neurology Central

Effects of LSD on the human brain imaged for the first time

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Imperial College London (UK) researchers have successfully visualized the effects of the psychedelic compound, termed Lysergic acid diethylamide or LSD, for the first time, following a series of experiments utilizing cutting-edge brain scanning techniques. The findings were published recently in Proceedings of the National Academy of Sciences.

The study included 20 healthy volunteers who received either 75 micrograms of LSD, or placebo, and underwent arterial spin labeling (ASL), blood oxygen level-dependent (BOLD) measures and magnetoencephalography (MEG).

Results indicated that increased visual cortex cerebral blood flow (CBF), decreased visual cortex alpha power and an expanded primary visual cortex (V1) functional connectivity profile was highly linked to ratings of visual hallucinations.

Skull with captionThese findings indicate that more general brain activity may exert more influence on, or contribute more strongly to, visual processing in the psychedelic state, leading to the well-known hallucinatory effects. Under normal conditions, this is restricted entirely to the visual cortex.

Lead author Robin Carhart-Harris explained: “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.  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.”

Despite this, decreased connectivity between the parahippocampus and retrosplenial cortex, which occurs under LSD, was strongly associated with experiences of ‘ego-dissolution’ and ‘altered meaning’.

Carhart-Harris commented: “this effect underlies the profound altered state of consciousness that people often describe during an LSD experience. It is also related to what people sometimes call ‘ego-dissolution’, which means the normal sense of self is broken down and replaced by a sense of reconnection with themselves, others and the natural world.”

“This experience is sometimes framed in a religious or spiritual way – and seems to be associated with improvements in well-being after the drug’s effects have subsided.”

“Our brains become more constrained and compartmentalized as we develop from infancy into adulthood, and we may become more focused and rigid in our thinking as we mature. In many ways, the brain in the LSD state resembles the state our brains were in when we were infants: free and unconstrained.”

The findings of the most recent study also link up with previous research carried out on the effects of listening to music while taking LSD. This research also highlighted changes in visual cortex activity when under the influence of LSD, with more information being received from the parahippocampus.

The team believe that these results from multiple studies may help to build the body of evidence supporting the potential efficacy of these psychedelic compounds in the treatment of psychiatric disorders such as depression or addiction where thought patterns are entrenched.

David Nutt (Imperial College London), who was the senior researcher on the study commented: “Scientists have waited 50 years for this moment – the revealing of how LSD alters our brain biology. For the first time we can really see what’s happening in the brain during the psychedelic state, and can better understand why LSD had such a profound impact on self-awareness in users and on music and art. This could have great implications for psychiatry, and helping patients overcome conditions such as depression.”

Source: Imperial College London press release; Carhart-Harris RL et al. Neural correlates of the LSD experience revealed by multimodal neuroimaging. PNAS, doi: 10.1073/pnas.1518377113.

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