tPBM in Older Adults With Traumatic Brain Injury

Inclusion Criteria: 1. Able to give written informed consent and follow study procedures. 2. Age ≥ 55 years and ≤ 85 years. 3. History of non-penetrating TBI of at least moderate severity, 1. defined by Emergency Department Glasgow Coma Scale (GCS) \< 13, 2. or post-traumatic amnesia \> 24 hours, 3. or loss of consciousness \> 30 minutes, 4. or evidence of trauma-related abnormality on acute neuroimaging. 4. Between 1 and 2 years post injury. Exclusion Criteria: 1. Delayed loss of consciousness due to expanding lesions 2. Diagnosis of dementia, history of brain tumor, or other serious neurological disorder 3. Diagnostic and Statistical Manual of Mental Disorders (DSM)-5 diagnosis of alcohol or drug use disorder or history of other major psychiatric illness diagnosed with Mini-International Neuropsychiatric Interview (MINI) 4. History of significant cardiovascular or cerebrovascular pathology before sustaining TBI 5. Unstable medical conditions or medications impacting cognition (e.g., topiramate) 6. Significant skin conditions on the subject's scalp in the area of illumination 7. Large bilateral prefrontal cortex (PFC) lesions (i.e., more than 50% of our middle frontal gyrus region of interest (ROI) in both hemispheres) 8. Claustrophobia or metallic foreign bodies that would preclude MRI 9. Unwilling/unable to comply with study as judged by the Principal Investigator 10. Body mass index \> 40 kg/m2 to fit comfortably in MRI 11. Past intolerance or hypersensitivity to tPBM 12. Any use of light-activated drugs (photodynamic therapy) within 14 days prior to study enrollment