Patient description: A 34 year old man comes to the clinic complaining of dizziness and severe diarrhea since yesterday. He has returned from an international trip few days ago and was living in a camp in Sudan for a month. He developed abdominal pain followed by bloating and nausea as well as loose bowel movements. Soon he was having profuse watery diarrhea without odor. The stool is watery and white but the patient has no fever. Blood pressure is 95/62 lying down and drops to 75/40 standing. The skin turgor has reduced. HR is 110 and he looks ill with dry mucosa. V. cholerae was seen in dark-field microscopy of a fresh stool specimen. The lab study is as bellow: Sodium 137 meq/L Potassium 2 meq/L Chloride 94meq/L CO2 15 meq/L Fecal leukocytes None seen Fecal occult blood Negative

Clinical trial eligibility criteria: eligible ages (years): 18.0-45.0,  Healthy Volunteer between 18 and 45 years old 2. right-handed. 3. Fluent in English. 4. able to provide written informed consent. 1. Has a dermatological condition such as scars, burns, callouses, or tattoos that might influence cutaneous sensibility on the hands 2. Has had recent or permanent injury of upper limbs or amputation or use of prosthetic arm or leg 3. Used recreational drugs within the past month 4. Is pregnant or breastfeeding. 5. Has a current chronic pain condition or has had chronic pain in the past (painful condition lasting more than six months). 6. Has a major medical condition, such as kidney, liver, cardiovascular, autonomic, pulmonary, or neurological problems (including blindness or deafness) or a chronic systemic disease (e.g. diabetes). 7. Has a medical condition potentially affecting somatosensation (e.g. Raynaud s Disease, peripheral neuropathy, or circulatory disorder). 8. Participant has or had psychiatric disorders such as major depression, major anxiety-related problems, substance or alcohol dependence or abuse, post-traumatic stress syndrome, bipolar disorder, psychosis, or suicide attempts or persistent suicide ideation. 9. Has metal implants or fragments in the body as this would make having an MRI scan unsafe. This includes pacemakers, medication pumps, aneurysm clips, metallic prostheses (such as metal pins and rods, heart valves or cochlear implants), shrapnel fragments, permanent eye liner or small metal fragments in the eye that welders and other metal workers may have. 10. Is uncomfortable in closed spaces (has claustrophobia) so that he/she would feel uncomfortable in the MRI machine, or a condition that prevents him/her from lying flat for up to 1 hour or rotating palm up for 15 minutes while lying flat. 11. Weight of 275 pounds or higher. 12. History of head trauma that was diagnosed as a concussion or was associated with loss of consciousness or was associated with loss of consciousness. 13. Personal history of a seizure or first degree relative with a seizure disorder 14. Participation in brain stimulation within one week of any TMS session in this study 15. Use of neuro-active drugs including opioids, antidepressants, anticonvulsants/antiepileptics, antipsychotics, dopamine agonists, sleep or anxiety medications, stimulants like methylphenidate (Ritalin), antihistamines, certain viral medications, or any other medication affecting the central nervous system 16. History of hearing loss 17. Obtained less than 6 hours of sleep the night before either TMS session (will be asked at each TMS session) 18. Consumed more than 16oz of coffee or an energy drink (anything with 500mg caffeine or more) on the day of the TMS session. (Caffeine > 500mg and sleep deprivation can increase seizure risk (Engel J, 2008). 19. Consumed alcohol on the day of the TMS session or shows signs of alcohol intoxication or alcohol withdrawal syndrome 20. Motor threshold over 82% of Magstim output