Inclusion Criteria:  Aged 18-45 years A first time, mild to moderate traumatic brain injury (TBI) When available, a Glasgow Coma Scale score between 9-15. Ability to use a keyboard Able to understand and communicate in English Be able to consent independently 6-24 months post traumatic brain injury Have the ability to leave a research visit with a companion/group transportation Women of child-bearing age must be comfortable confirming a negative pregnancy prior to participating in the study. Not involved in any other research intervention study testing neurobehavioral functioning  Exclusion Criteria:  Other neurological diagnoses or a diagnosis of severe psychiatric disorder (e.g., psychosis) or a reported childhood learning disability Severe aphasia, preventing an understanding the protocol and consent form Pre-existing hypoxic pulmonary disease Severe hypertension (>160/100) Medically documented history of obstructive lung diseases [e.g., Chronic obstructive pulmonary disease (COPD) or significant asthma] Ischemic cardiac disease. Ineligible to undergo MRI, TMS, or EEG