The Stanford radiological sciences laboratory is looking for people to participate in a brain stimulation research study. This study aims at developing the methodology for combining a brain stimulation method, transcranial electrical stimulation (tES) with a method for mapping brain activity, functional magnetic resonance imaging (fMRI). tES delivers a weak current (< 2mA) to the brain through electrodes placed upon the scalp. fMRI noninvasively images brain functions by applying a strong magnetic field and radiofrequency magnetic fields, and can be utilized to localize and detect brain functional changes induced by tES. Depending on the setting of the experiments, you will be asked to complete a few tasks (e.g., cognitive engagement, sensory stimulus, or quietly resting) while lying inside the scanner. TES will be delivered either before, during and/or after MR scans. The study will be conducted at The Richard M. Lucas Center for Imaging, Stanford University. * The following set of characteristics describe individuals who are particularly vulnerable to COVID-19, and who therefore are not allowed to participate in this research study: a. Individuals over the age of 65, unless they are already coming in to Stanford Health Care for a medical visit b. Any individual with an underlying medical condition for which the CDC says they are at increased risk of severe illness from COVID-19, unless the individual is participating in a clinical trial or clinical research investigating their medical conditions. As of October 20, this list includes: Cancer, Chronic kidney disease, COPD, Heart conditions, Immunocompromised state, Obesity, Severe Obesity, Sickle cell disease, Smoking, and Type 2 diabetes mellitus. This study (including preparation) will take up to 2 hours. You will receive $15 per hour for participating in this study. If you would like to participate, please e-mail for further information. Thanks!