Contributions of mTBI to Neurodegeneration Due to Chronic Traumatic Encephalopathy (CTE) and Alzheimer's Disease (AD)

Inclusion Criteria: All Subjects: * Intact color vision * Visual acuity of 20/30 (or better) * Patients must pass effort measures on the TOMM * Patients must have intact decision-making capacity * Patients must have no contraindications to lumbar puncture including: * Being on a blood thinner * Aspirin or Plavix * Have no space occupying lesion on magnetic resonance imaging (MRI) * An International Normalized Ratio (INR) value \< 1.4 and platelet count \>50,000 * No epidural infection or overlying cellulitis over the lumbar spine * PTSD will be accounted for as a potential confounder and its presence will be included as a covariate in all analyses Mild TBI Subjects: * Subjects will be recruited who have a physician diagnosis of 1 or more mTBI episodes without concomitant moderate or severe TBI diagnosis * Mild TBI: Loss of consciousness greater than 30 minutes, posttraumatic amnesia greater than 24 hours, and/or altered mental status greater than 24 hours Moderate TBI Subjects: * Subjects will be recruited who have a physician diagnosis of 1 or more moderate TBI episodes * Moderate TBI: loss of consciousness greater than 30 minutes, posttraumatic amnesia greater than 24 hours, and altered mental status greater than 24 hours MCI Subjects: * Subjects will be recruited that meet diagnostic criteria for MCI (without a history of TBI) based on the judgement of a behavioral neurologist following the 2011 MCI criteria * Specifically, subjects will test in the impaired range …