MoodBugs_Rifaximin

You likely can't join if

• 1. Participant has a history of previous or current neurological, psychiatric, gastrointestinal or endorcrine disorder 2. Any disorder, which in the Investigator’s opinion might jeopardise the participant’s safety or compliance with the protocol 3. Any prior or concomitant treatment(s) that might jeopardise the participant’s safety or that would compromise the integrity of the Trial 4. Participation in an interventional Trial with an investigational medicinal product (IMP) or device 5. Hypersensitivity to the active substance rifaximin, to any rifamycin (e.g. rifampicin or rifabutin) or any of the excipients (see Section 5.1) 6. Current or recent medication use 7. Use of antibiotics within three months preceding the study 8. Current or recent (1-month) infection (e.g. common cold, influenza, COVID-19, etc.) 9. Recent (1-month) vaccination (e.g. flu shot, SARS-COV-2 vaccine, etc) 10. Previous or current substance/alcohol dependence or abuse (>2 units per day or 14 units per week) 11. One or more diagnoses based on the mini international neuropsychiatric interview 12. One or more diagnoses based on ROME IV for gastrointestinal disorders 13. Smoking 14. Night-shift work 15. Adherence to special diets (e.g. vegan, vegetarian, weight-loss, lactose-free, gluten-free, etc.) 16. Use of pre- or probiotics within one month preceding the study 17. Previous experience with any of the tasks used in the study (not including questionnaires) 18. Color vision deficiency (colorblindness) Additional exclusion criteria for participants partaking in the brain imaging part of the study: 1. Claustrophobia or too much uneasiness in limited spaces (in order to tolerate confinement during the scanning procedures). 2. Severe back problems interfering with lying in supine position in the scanner with no movement for long durations. 3. Any condition that would interfere with MRI studies (e.g., cochlear implant, metal fragments in eyes, cardiac pacemaker, neural stimulator, and metallic body inclusion or other metal implanted in the body which may interfere with MRI scanning). To check this, participants fill out a checklist before the procedure (see Appendix). 4. If the participant invokes that he does not want to be informed of eventual pathology that might be found during imaging (invokes the “right not to know”)