The physical effects of magic mushrooms

Researchers have examined the brain effects of the psychedelic chemical in magic mushrooms, called ‘psilocybin’, revealing the physical changes the chemical makes to the brain. Their work has been published in the journal Human Brain Mapping.

Users of psychedelic drugs often describe ‘expanded consciousness’, including enhanced associations, vivid imagination and dream-like states. To explore the biological basis for this experience, the researchers analysed brain imaging data from 15 volunteers who were given psilocybin (and later a placebo) intravenously while they lay in a functional magnetic resonance imaging (fMRI) scanner.

The study examined variation in the amplitude of fluctuations in what is called the blood-oxygen level dependent (BOLD) signal, which tracks activity levels in the brain. This revealed that activity in important brain networks linked to high-level thinking becomes unsynchronised and disorganised under psilocybin. One particular network that was especially affected plays a central role in the brain, essentially ‘holding it all together’, and is linked to our sense of self.

Meanwhile, activity in the different areas of a more primitive brain network became more synchronised under the drug, indicating they were working in a more coordinated, ‘louder’ fashion. The network involves areas of the hippocampus (associated with memory and emotion) and the anterior cingulate cortex (related to states of arousal), which were active at the same time in a pattern of activity similar to that observed in people who are dreaming.

Dr Robin Carhart-Harris, from Imperial College London, said he was “fascinated to see similarities between the pattern of brain activity in a psychedelic state and the pattern of brain activity during dream sleep, especially as both involve the primitive areas of the brain linked to emotions and memory. People often describe taking psilocybin as producing a dream-like state and our findings have, for the first time, provided a physical representation for the experience in the brain.”

Following initial data collection at Imperial College London in 2012, specialists in the mathematical modelling of brain networks - Professor Dante Chialvo from CONICET and Dr Enzo Tagliazucchi from Goethe University - were recruited to investigate how psilocybin alters brain activity to produce its unusual psychological effects. As part of the new study, the researchers applied a measure called entropy, which can be used to measure the range or randomness of a system.

The researchers computed the level of entropy for different networks in the brain during the psychedelic state. This revealed an increase in entropy in the more primitive network, ie, an increased number of patterns of activity that were possible under the influence of psilocybin. The volunteers appeared to have a much larger range of potential brain states that were available to them, which may be the biophysical counterpart of ‘mind expansion’ reported by users of psychedelic drugs.

Previous research has suggested that there may be an optimal number of dynamic networks active in the brain, possibly optimising the balance between the stability and flexibility of consciousness. The mind works best at a critical point when there is a balance between order and disorder and the brain maintains this optimal number of networks. When the number goes above this point, the mind tips into a more chaotic regime where there are more networks available than normal. The latest results suggest that psilocybin can manipulate this critical operating point.

“Psychedelic drugs … are powerful tools for exploring what happens in the brain when consciousness is profoundly altered,” said Dr Tagliazucchi. “It is the first time we have used these methods to look at brain imaging data and it has given some fascinating insight into how psychedelic drugs expand the mind.”

“Learning about the mechanisms that underlie what happens under the influence of psychedelic drugs can also help to understand their possible uses,” added Dr Carhart-Harris. “We are currently studying the effect of LSD on creative thinking and we will also be looking at the possibility that psilocybin may help alleviate symptoms of depression by allowing patients to change their rigidly pessimistic patterns of thinking. Psychedelics were used for therapeutic purposes in the 1950s and 1960s but now we are finally beginning to understand their action in the brain and how this can inform how to put them to good use.”

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