The purpose of this study is to evaluate the effect of transcranial photobiomodulation (tPBM) in older patients with chronic traumatic brain injury (TBI). The study aims to examine the effect of tPBM on prefrontal cerebral blood flow (CBF) and executive function (EF)

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

The de-identified participant data from the final research dataset will be shared upon reasonable request beginning 9 to 36 months after publication or as required by a condition of awards or supporting agreements, provided the requesting investigator executes a data use agreement with NYU Langone Health. This instance of data sharing will also require separate IRB review as well as review from NYU Langone's Data Sharing Strategy Board (DSSB). Requests should be directed to: jkim@med.cuny.edu. The protocol and statistical analysis plan will be posted on Clinicaltrials.gov only as required by federal regulation or supporting awards and agreements.

Beginning 9 months and ending 36 months following article publication or as required by a condition of awards and agreements supporting the research.

The investigator who proposed to use the data will be granted access upon reasonable request. Requests should be directed to jkim@med.cuny.edu. To gain access, data requestors will need to sign a data access agreement. This instance of data sharing will also require separate IRB review as well as review from NYU Langone's DSSB.