Methods: I) Balance Assessment: To characterize balance deficits in people with mTBI who have chronic, non-resolving balance deficits compared to healthy control subjects without a history of mTBI. We hypothesize that a) objective measures of central sensorimotor integration, static and dynamic balance will better distinguish people with mTBI from control subjects than clinical measures, b) a subset of people with mTBI will have abnormal central sensori-motor integration (CSMI) test measures, even without peripheral vestibular or ocular motor deficits c) the relationship between poorer static/dynamic balance performance and mTBI is regulated/mediated by CSMI. We will test 130 subjects between the ages of 18 and 60; 65 with chronic (> 3 months) mTBI and non-resolving balance deficits and 65 healthy age and gender matched control subjects without a history of mTBI. We will obtain objective measures of static and dynamic balance using wearable inertial sensors and determine how these measures relate to central sensorimotor integration. We will also obtain laboratory measures of peripheral vestibular function and ocular motor function to help classify people and to consider as potential covariates in rehabilitation efficacy.