PET Imaging of Neuroinflammation in Neurodegenerative Diseases Via a Novel Translocator Protein (TSPO) Radioligand

* INCLUSION CRITERIA: 1\. Patients will be included if they * Are age 18 or older * Have the ability to understand and sign an informed consent, or have a DPA or a court-appointed guardian (or be able to understand the DPA process to appoint a DPA) to provide consent for adults without consent capacity * Have been given a diagnosis by a neurologist of frontotemporal dementia, frontotemporal lobar degeneration, primary progressive aphasia, semantic dementia, motor neuron disorder, amyotrophic lateral sclerosis, primary lateral sclerosis, progressive bulbar palsy, corticobasal syndrome, Huntington disease, Alzheimer s disease, or other related adult-onset neurodegenerative disease 2\. Subjects with an increased risk of neurodegenerative diseases will be included if they * Are age 18 or older * Are able to give written informed consent * Have known family history or other risk of an adult-onset genetic neurodegenerative disease, and/or mutation in a gene known to cause an adult-onset neurodegenerative disease 3\. Healthy subjects will be included if they * Are age 18 or older * Are willing and able to complete all study procedures * Are able to give written informed consent * Are medically healthy * Are enrolled in 01-M-0254 The Evaluation of Participants with Mood and Anxiety Disorders and Healthy Volunteers (PI: Dr. Carlos Zarate) or 17-M-0181, Recruitment and Characterization of Healthy Research Volunteers for National Institute of Mental Health (NIMH) Intramural Studies (PI: Dr. Joyce Chung) EXCLUSION CRITERIA: 1. Patients or subjects with an increased risk of neurodegenerative diseases will be excluded if they * Have other major neurological or medical diseases that may cause progressive weakness or cognitive dysfunction, such as structural brain or spinal cord disease, metabolic diseases, paraneoplastic syndromes, infectious diseases, peripheral neuropathy or radiculopathy or other significant neurological abnormalities * Have an unstable medical condition that, in the opinion of the investigators, makes participation unsafe (e.g., active infection or untreated malignancy) * Require daytime ventilator support at the time of study entry * Are unable to travel to NIH * Have recent exposure to radiation related to research (e.g., PET from other research) that, when combined with this study, would be above the allowable limits * Have inability to lie flat and/or lie still on camera bed for at least two hours, including claustrophobia, overweight greater than the maximum for the scanner, and uncontrollable behavioral symptoms, which will be screened by an interview with patient and/or caregiver during the screening visit * Are pregnant or breastfeeding * Participants must not have substance use disorder or alcohol use disorder. However, alcohol or cannabis use by themselves are not exclusion criteria, unless that use impairs function * Are unable to have an MRI scan (e.g., pacemakers or other implanted electrical devices, brain stimulators, 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, implanted delivery pumps, or shrapnel fragments, metal fragments in the eye) * NIMH employees/staffs or NIH employees who are subordinates/relatives/co-workers of investigators 2. Healthy subjects will be excluded if they * Have any history of medical illness or injury with the potential to affect study data interpretation or to be any medical contraindication to the procedures performed in the study, including active infection and untreated malignancy. * Have clinically significant laboratory abnormalities based on test performed under screening protocol 01-M-0254 or 17-M-0181 * Have recent exposure to radiation related to research (e.g., PET from other research) that, when combined with this study, would be above the allowable limits * Have inability to lie flat on camera bed for at least two hours, including claustrophobia and overweight greater than the maximum for the scanner * Are pregnant or breastfeeding * Participants must not have substance use disorder or alcohol use disorder. However, alcohol or cannabis use by themselves are not exclusion criteria, unless that use impairs function * Are unable to have an MRI scan (e.g., pacemakers or other implanted electrical devices, brain stimulators, 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, implanted delivery pumps, or shrapnel fragments, metal fragments in the eye) * NIMH employees/staffs or NIH employees who are subordinates/relatives/co-workers of investigators