The Role of 5-HT2A Receptor in the Perception of Self and Personal Meaning in Healthy Volunteers

Inclusion Criteria: * Healthy male and female volunteers at the age of 20-40 * Willing and capable to give informed consent for study participation as documented by signature after the nature of the study has been thoroughly explained * Willing to refrain from drinking alcohol the day before testing session, from drinking alcohol and caffeinated drinks at the testing days and from consuming psychoactive substances 2 weeks before testing days and for the duration of the study * Able and willing to comply with all study requirements * MRI-compatible body shape and size (Body mass index \[BMI\] 17-30) * Right-handedness Exclusion Criteria: * Poor knowledge of the German language * Previous significant adverse response to a hallucinogenic drug * Participation in another study where pharmaceutical compounds are given within the 30 days preceding and during the present study * Self or first-degree relatives with present or antecedent psychiatric disorders * Present or antecedent alcohol/drug dependence or present alcohol/drug abuse * History of head trauma, fainting, seizures, or electroconvulsive therapy * Recent cardiac or brain surgery * Current use of medication known to affect brain function (e.g. benzodiazepines, antihistamines, aspirin, beta blockers, theophylline, acetazolamide, etc.) * Concomitant therapy with potent inhibitors of cytochrome P-450 isoenzyme 3A4 (HIV protease inhibitors, macrolide antibiotics, acylderivative anti-infective agents) * Presence of major internal or neurological disorders (including sepsis, pheochromocytoma, thyrotoxicosis, drug-induced fibrosis, familiar or basilar artery migraine) * Presence of psychiatric disorder * Cardiovascular disease (hypertonia, coronary artery disease, heart insufficiency, myocardial infarction within the past 6 months, coronary spastic angina) * Peripheral vascular disease (thromboangiitis obliterans, luetic arteritis, severe arteriosclerosis, thrombophlebitis, Raynaud's disease) * Liver or renal disease * Pregnant or breastfeeding women (a urine pregnancy test will be done before each session for all women capable of bearing children) * Inability to lie still for about 60 minutes (e.g. because of sneezing, itching, tremor, pain) * Metal parts in the body (piercings, brain aneurysm clip, implanted neural stimulator/cardiac pacemaker/defibrillator/Swan Ganz catheter/insulin pump, cochlear implant); metal shrapnel or bullet, ocular foreign body (e.g. metal shavings); current or previous job in metalworking industry * Claustrophobia