Scientists at the University of Basel have shown for the first time that taking a moderate dose of LSD modulates the activity of the emotional centers in the brain, raising the threshold for fear.
D-lysergic acid diethylamide (LSD) is a semi-synthetic psychoactive substance, the intake of which causes temporary profound changes in self-awareness, perception and emotions, for example, reduces anxiety. It is assumed that the effects of this psychedelic (by analogy with mescaline and psilocybin) are associated with agonism at serotonin 5-HT2A receptors, the activation of which increases the level of dopamine in the prefrontal cortex. Nevertheless, the effect of LSD on the brain and psyche has not been sufficiently studied: since 1971, in many countries of the world, the substance has been included in the list of prohibited narcotic substances. At the same time, despite the absence of a direct ban on clinical research, the use of psychedelics for scientific purposes is formally limited.
In a new article, the experiment with LSD was described by scientists from Switzerland - in 2008 the Confederate authorities relaxed the ban on its study for therapeutic purposes. The aim of the work was to find out how the substance affects the areas of the brain involved in the processing of emotions. To this end, the authors conducted a double-blind, randomized, placebo-controlled, crossover study in which 20 volunteers took part. According to the test protocol, each participant underwent two 25-hour sessions, during which they took 100 micrograms of LSD in a gelatin capsule or a similar dose of mannitol. 2.5 hours after taking the drug or placebo, their brains were scanned using functional magnetic resonance imaging (fMRI).
Neural response to neutral and frightening stimuli after taking placebo (red) and LSD (yellow) / © F. Mueller et al., Translational Psychiatry, 2017
While connected to the tomograph, the subjects underwent a six-minute test, in which they were shown 60 images of faces with fear grimaces of varying intensity - from 50 to 100 percent - from Paul Ekman's POFA collection (Paul Ekman). To maintain attention at this stage, the volunteers had to press the left or right button in accordance with the sex of the person shown - the accuracy of the answers and the reaction time were recorded. Analysis of the test results did not reveal significant differences between the groups in these parameters. In turn, fMRI revealed bilateral activation of the cerebellum, fusiform gyrus, and occipital gyrus on image viewing, with the left fear grimace amygdala activating only after placebo.
LSD ingestion reduced the response of the amygdala and medial frontal gyrus in response to display of neutral and intimidating faces. In addition, the authors found a significant negative correlation between the oxygen-dependent blood level in the amygdala of the subjects who took the drug and the subjective experience of its action. According to scientists, the findings indicate that LSD can raise the threshold for fear, and this indicator is likely to be dose-dependent. In the future, this property of the compound can be used in medicine, and the researchers intend to continue studying its therapeutic properties. The amygdala is a part of the limbic system located in the temporal lobe of the brain. Its hyperactivity is often associated with anxiety disorders, as well as other diseases, such as the risk of stroke.
Details of the work are presented in the journal Translational Psychiatry.
Denis Strigun
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