## 2 Materials and Methods  
All subjects submitted their informed consent for inclusion before they participated in the study. The study was conducted in accordance with the Declaration of Helsinki, and the protocol was approved by the Biomedical Institutional Review Board Committee at the University of Nevada, Las Vegas (NV, USA; protocol no. 1048342). This study had a cross-sectional descriptive design to compare different functional levels and blood 5-mC% between voluntary college student participants with and without a self-reported history of mTBI. Both males and females aged 18 years or older were recruited. Specific inclusion criteria for mTBI cases were an exposure to a close head (no skull fracture) trauma that resulted in loss of consciousness less than 30 min and post-traumatic amnesia less than 24 h. Those who were medically diagnosed with any other neuro-psychiatric diseases (e.g., multiple sclerosis, ADHD, cerebral palsy) or on non-prescription drugs and alcohol use 24 h before testing were excluded. This study was advertised by flyers on the UNLV campus as well as via email blasts advertisement to the members of the Military and Veteran Services Center from the director at the center. After an initial phone interview all subjects meeting the inclusion criteria participated in a series of recorded procedures aimed to establish their levels of oculomotor efficacy, cognitive and psychological functions, balance control, and 5-mC% via blood sample. All procedures took 2.5 h. Each subject was compensated with $25 cash for his or her time and effort in completing the data collection. Tools and measures used in this study are as follows: First, _the Rivermead post-concussion symptom questionnaire_ (_RPQ_) [40] and _the neurobehavioral symptom inventory_ (_NSI_) [41] were used to evaluate overall post-mTBI symptoms. The RPQ contains 16 items on premorbid functioning by means of written self-report or in-person or telephone interview. The RPQ has a high test-retest reliability (_r_, ranged: 0.87-0.91) [40] and has been used most often in assessing mTBI-related symptoms at all levels of severity in individuals with mild, moderate, and severe TBI. The NSI has 22 items to cover a comprehensive range of the symptom domains (physical, cognitive, affective, and sensory) [41; 42] and has good-to-excellent reliabilities across domains (_r_, ranged: 0.77-0.93). Both RPQ and NSI have been widely used with various clinical samples with mTBI or concussion, including active military service members and veterans [6; 41; 43]. _The NIH toolbox_[44] with computer generated cognitive tasks was used to measure cognitive function. The six following modules from the NIH toolbox were used to evaluate short-term memory, recognition of patterns, and spatial recognition ([[http://www.healthmeasures.net/explore-measurement-systems/nih-toolbox](http://www.healthmeasures.net/explore-measurement-systems/nih-toolbox)]([http://www.healthmeasures.net/explore-measurement-systems/nih-toolbox](http://www.healthmeasures.net/explore-measurement-systems/nih-toolbox))): Dimension Change Card Sort Test (DCCS) for executive function, Flanker Inhibitory Control and Attention Test for executive function and attention, Picture Sequence Memory Test for episodic memory, List Sorting Working Memory Test for working memory, Picture Vocabulary Test for vocabulary knowledge, and Pattern Comparison Processing Speed Test for processing speed. Two additional scores were also included: Fluid Cognition Composite Score based on DCCS, Flanker, Picture Sequence, List Sorting, and Processing modules; and Early Childhood Composite Score based on DCCS, Flanker, Picture Sequence, and Picture Vocabulary. All modules were developed and validated by the NIH with state-of-the-science methodology. The NIH toolbox has shown excellent reliability and validity with various populations with good-to-excellent reliabilities (_r_, ranged: 0.78-0.99) [44].