Inclusion Criteria:  I am between the ages of 18 and 65. I have a diagnosis with moderate to severe TBI. I am at least one year post injury. I am able to speak and read English fluently.  Exclusion Criteria:  I have a history of multiple sclerosis, stroke, seizures or another neurological injury or disease in the past (like brain tumor or epilepsy). I have a history of significant psychiatric illness (like bipolar disorder, schizophrenia or psychosis). I am currently taking steroids and/or benzodiazepines as determined by study staff review of my medications.