Normative Datasets for Assessments Planned for Mild Traumatic Brain Injury (NORMAL)

Inclusion Criteria: * Active duty or civilian in the Colorado Springs area. * Men 18-65 years old and women 18-35 years old at the time of enrollment. * Able to speak and read English, as primary language. * Agrees to, and appears able to participate in all outcome assessments. * Agrees to provide blood samples for laboratory tests and specimen banking. * Demonstrates the ability to offer informed consent and signs the study informed consent document. * No known brain imaging abnormalities. * Known history of full term non-complicated birth. * Estimated glomerular filtration rate (eGFR) \>90. Exclusion Criteria: * Prisoners. * Pregnant Women. * Minors. * Civilian participants with planned leave conflicting with study visits or relocation within 6 months of study enrollment, and unwilling or unable to return for follow up. * Active duty participants with planned leave or deployment conflicting with assessment intervals. * Any lifetime history of brain injury. * Diagnosis of, or a persistent history of, or symptoms of a neurological disorder (e.g., tinnitus, vertigo, chronic fatigue, numbness, tingling, chronic migraine, fibromyalgia, multiple sclerosis). * Active therapy for affective disorders, behavioral disorders, or psychological disorders. * Diagnosis of diabetes mellitus * Current complaints of brain injury symptoms such as cognitive or affective problems. * Diagnosis of recurrent migraine or cluster headaches that are under medical management. * Headaches that occur more than two times per week. * Recurrent dizziness that requires medical management. * Dizziness more than two times per week. * History of theater or war zone activity that placed the participant within a combat zone environment. * Diagnosis of PTSD or sub-clinical post-traumatic symptoms. * Known neuroimaging abnormalities. * Use of daily prescription drugs that could impact a normal outcome (e.g., beta blockers, antidepressants), with the following exceptions: * Participants who are 45 or more years old may be taking statins or ACE inhibitors. * Oral or injectable contraceptives are permitted * Participants \<45 years old who are taking any daily prescriptions (exception - oral or injectable contraceptives) * Known atrial septal defect. * History of hydrocephalus/microcephaly/macrocephaly. * History of developmental delay or learning disorder as a child. * Women who are breastfeeding. * Women of childbearing potential who do not agree to practice an acceptable form of birth control during the study period. * Allergy to iodine-based contrast dye (exclusion criteria for neuroimaging assessment measures). * Those who are unable to participate fully in outcome assessments unless enrollment is reviewed and approved (in writing) by the Study Director. * Binocular vision not correctable to 20/50. * Deafness in both ears defined as 90 decibel hearing loss or greater through speech frequencies. * Anxiety or claustrophobia precluding participation in neuroimaging or vestibular procedures. * History of therapeutic ionizing radiation to the head. * Foreign material in head that would interfere with brain imaging. * Foreign material within the individual that poses risk from MRI. * History of illicit drug use, except remote, non-habitual use of marijuana. * History in the last year, of alcohol abuse. * Current positive urine test for an illicit substance(s). * Active or prior malignancy except basal cell carcinoma within the last 5 years. * Unable to abstain from caffeine or tobacco products for at least a 2-hour interval. * Concurrent enrollment in any other research trial. * Unable or unwilling to cease participation in sports or activities in which head injury is likely (e.g., mixed martial arts, boxing) during the study period.