A new neuroimaging study found that psilocybin reduces the brain’s amygdala region response to seeing pictures of angry faces. In contrast, neural responses to fearful and neutral faces were unaffected. The research was published in Neuroscience Applied.
Psilocybin is a naturally occurring psychedelic compound found in certain species of mushrooms, commonly known as “magic mushrooms.” It is known for its psychoactive properties, which can induce altered states of consciousness, including changes in perception, mood, and thought patterns. Psilocybin has been used for centuries in various cultural and religious practices for its spiritual and introspective effects. In recent years, it has gained attention in the medical community for its potential therapeutic benefits in treating mental health conditions such as depression, anxiety, and posttraumatic stress disorder.
Researchers studying the subjective effects of psilocybin report that its use can result in deep-felt feelings of love and peacefulness, emotional acceptance rather than avoidance, increased emotional empathy, and reexperiencing various emotional memories. Overall, psilocybin seems to be able to change one’s emotional state. This means that it might be able to affect regions of the brain involved in processing emotions, such as the amygdala.
The amygdala, a small, almond-shaped region in the brain, is crucial for processing emotions, especially those related to fear and anxiety. It plays a significant role in the formation of emotional memories and the modulation of emotional responses. The amygdala’s activity affects behaviors like aggression, avoidance, and social interactions.
In their new study, Sophia Armand of the University of Copenhagen and her colleagues conducted an experimental neuroimaging study to determine whether a medium-high dose of psilocybin would affect the amygdala’s response to emotionally expressive faces.
The study involved 28 healthy individuals recruited from a pool of volunteers interested in psychedelic research. Each participant took part in two sessions, spaced at least 21 days apart. In one session, they received a dose of 0.2-0.3 mg/kg of psilocybin, administered in 3 mg capsules, while in the other, they received 20 mg of ketanserin, a drug used to treat hypertension and investigate the role of serotonin in physiological and psychological processes. (The effects of ketanserin were not reported in this paper.)
At the beginning of the study, participants underwent functional magnetic resonance imaging (fMRI) while completing a variant of the emotional faces task, which involved identifying emotions on faces displaying fear, anger, surprise, or neutrality in random order. The researchers measured neural activity in the amygdala during these tasks. Additionally, participants were assessed for intelligence, body mass index, mood, sleep quality, and stress level.
On the day they received psilocybin, participants repeated the fMRI and emotional faces task, enabling researchers to compare brain activity under the substance’s influence to their baseline state.
Results showed that the response of the amygdala region of the brain to angry faces was significantly decreased when participants were under the influence of psilocybin. Reactions to fearful and neutral faces were also somewhat decreased, but the decrease was small and not statistically significant. (In other words, the small effect did not allow the researchers to conclude that it was not just a random variation.) However, participants who reported feeling stronger effects of the drug tended to have more reduced amygdala reactions to fearful faces.
The accuracy of responses in the emotional faces task was the same both when participants were under the influence of psilocybin and when they were not.
“As hypothesized, we found that the amygdala response to angry faces was significantly reduced but remained unchanged to neutral faces using BOLD fMRI [blood oxygen level dependent functional magnetic resonance imaging] following acute administration of psilocybin in healthy individuals. Consistent with our hypothesis, we also find that amygdala response to fearful faces is negatively associated with SDI [subjective drug intensity],” the study authors concluded.
The study sheds light on the effects of psilocybin on amygdala responses to emotional faces. However, the study was conducted on a very small group of participants and the emotional faces task is based on pictures. Neural responses to real people displaying real emotions might not be the same.
The paper, “Amygdala response to emotional faces following acute administration of psilocybin in healthy individuals,” was authored by Sophia Armand, Kristian Larsen, Martin K. Madsen, Brice Ozenne, Katrin H. Preller, Gitte M. Knudsen, Dea S. Stenbaek, and Patrick M. Fisher.
