Cognitive and Electrophysiological Assessment of Non-Invasive Temporally-Interfering Electric Fields Stimulation (TIEFS)

The goal of this clinical trial is to learn how a non-invasive brain stimulation method called Temporally Interfering Electric Fields Stimulation (TIEFS) affects brain activity and thinking in adults. TIEFS uses electrical currents applied to the scalp to influence brain activity without surgery. The main questions this study aims to answer are: * How does TIEFS change brain signals measured with brain recordings? * Does TIEFS affect thinking abilities such as memory, language, movement, or perception? * Is TIEFS safe and well tolerated when used in people? This study includes two groups of participants. One group includes adults with epilepsy who are already undergoing specialized brain monitoring as part of their medical care. The other group includes healthy adults with no history of seizures. Participants will: * Receive brief sessions of TIEFS using electrodes placed on the scalp * Complete computer-based tasks that test memory, attention, language, or movement. Answer questions about how the stimulation feels * Have brain activity recorded during the study Each study visit lasts up to three hours and may occur in one or two sessions. Information from this study may help researchers better understand the human brain and support the development of future non-invasive brain stimulation treatments.