The aim of the present study is to assess the neuronal correlates of alterations in waking consciousness pharmacologically induced by a 5-hydroxytryptamine (HT)2A receptor agonist in healthy subjects using functional magnetic resonance imaging (fMRI).

Functional neuroimaging may be useful in the diagnosis and characterization of early schizophrenia. However, little is known about how the subjectively experienced alterations in consciousness and perception are related with objective neuroimaging measures. The present study explores the association of subjective alterations and objective imaging findings and will inform us on the neuronal correlates of psychotic states and whether subjective alterations in perception translate into neuronal activation patterns that can be objectively measured in a brain scanner. Therefore, alterations in consciousness will be assessed in 20 healthy subjects using a random order 2-period (normal and altered state of consciousness) cross-over design. Alterations in consciousness will be induced by the hallucinogenic 5-hydroxytryptamine (HT)2A receptor agonist (5-HT2A) receptor agonist lysergic acid diethylamide (LSD).

Inclusion Criteria:

1. Age between 25 and 65 years
2. Understanding of the German language
3. Understanding the procedures and the risks associated with the study
4. Participants must be willing to adhere to the protocol and sign the consent form
5. Participants must be willing to refrain from taking illicit psychoactive substances during the study.
6. Participants must be willing to drink only alcohol-free liquids and no xanthine-containing liquids (such as coffee, black or green tea, red bull, chocolate) after midnight of the evening before the study session, as well as during the study day.
7. Women of childbearing potential must have a negative pregnancy test at the beginning of the study and before each study session.

Exclusion Criteria:

1. Chronic or acute medical condition
2. Current or previous major psychiatric disorder
3. Psychotic disorder in first-degree relatives
4. Illicit substance use (except tetrahydrocannabinol (THC)-containing products) more than 10 times or any time within the previous month.
5. Pregnant or nursing women.
6. Participation in another clinical trial (currently or within the last 30 days)