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