Objective The objective of the protocol is to determine the test-retest reliability of imaging techniques that measure the structural and functional integrity of the motor cortex in healthy subjects. Our goal is to determine whether such measures are sufficiently reproducible that they may be used to follow disease progression over time in patients with motor neuron disease. A second objective is to obtain age-matched normative data to provide reference values for studies examining the correlation of physiological and clinical measurements of motor function, cognitive testing, and plasma and spinal fluid biomarker measures with disease progression in patients with motor neuron disease. Study Population 55 neurologically normal, healthy adults, age 35 or older Design Each subject will undergo several sessions of testing. The first testing session will consist of a clinical examination with measurements of movement speed. Subjects will undergo one session with transcranial magnetic stimulation of the brain, one session of cognitive testing, and three sessions of magnetic resonance imaging of the brain, one to eighteen months apart. Subjects may opt-in for collection of blood and spinal fluid to provide controls for biomarker studies in motor neuron disease patients. Outcome Measures The primary outcome is the test-retest reliability of magnetic resonance imaging measurements of the motor cortex in individual subjects.
- INCLUSION CRITERIA: - Healthy adults aged 35 and older - No history of a neurological disorder - Able to give informed consent EXCLUSION CRITERIA: - Treatment within the preceding week with medications that affect neuronal excitability, such as antidepressants, sedatives, and drugs for epilepsy or migraine. - Change in blood pressure medications within the preceding week. - Metal in the body such as pacemakers, implanted pumps or other implanted electronic devices, some types of dental implants, aneurysm clips (metal clips on the wall of a large artery), metallic prostheses (including metal pins and rods, heart valves, and cochlear implants), permanent eyeliner or shrapnel fragments. - Pregnancy. Women of childbearing potential will undergo urine pregnancy testing before MRI scanning. - Fear of confined spaces. - Serious medical illness. - Employees or staff in the investigator's section.