RecruitingDevice studyPower Nap With TES-TIThe goal of this clinical trial is to find out whether stimulating the brain with electrical current during naps can increase certain kinds of brain activity that happen during sleep and lead to improvements in mental fatigue. Participants will attend 2 study visits, each of which may last up to 4-5 hours. During these visits, participants will wear a high density electroencephalography (hdEEG) cap and take a nap.