Inclusion Criteria:  (1) Have a remote history mild traumatic brain injury as defined by the VA/DoD clinical practice guidelines(The Management of Concussion/mTBI Working Group, 2016) that is >/= 6 months, and report moderate severity neurocognitive symptoms related to attention, concentration, working memory, or memory based on NSI scores and self-report. (2) Are between the ages of 18-55. (3) Are stable on any medications for at least 2 weeks at the baseline visit (Visit #1).  Exclusion Criteria:  (1) Have a history of seizures or epilepsy. (2) Have a history of ECT or cortical energy exposure within the past 12 months, including participation in any other neuromodulation studies. (3) Have current stimulant dependence. (4) Have a diagnosis of intellectual disability or pervasive developmental disorder (i.e. premorbid IQ less than or equal to 70). (5) Have any medical condition or treatment other than mild TBI (e.g. stroke, tumor, HIV, moderate-severe TBI), with significant neurological disorder or insults that, based on the Principal Investigator's judgement, would impact risk. (6) Diagnosed with current active psychosis or mania. (7) Have metallic cranial plates/screws or implanted device, (8) Have eczema on scalp or other scalp lesions or skin disorders that may become irritated by stimulation. (9) Pregnant individuals and individuals with ferromagnetic metal in their body that would prohibit them from being safe in the MRI will not be excluded from the overall study, but will be excluded from the optional MRI.