RecruitingDiagnostic testMagnetoencephalography (MEG) Pilot StudyThe purpose of this research is to learn more about how the brain works in people with essential tremor, and how it changes after treatment with High-Intensity Focused Ultrasound (HiFU). Essential tremor is a movement disorder that causes shaking, usually in the hands, and can make everyday tasks difficult. HiFU is a treatment that uses focused sound waves to target a small area in the brain involved in tremor. In this study, the investigators aim to understand how this treatment affects the brain's networks by using safe, non-invasive tests such as brain imaging, brain wave recordings, and movement assessments.