Transcranial Photobiomodulation for Alzheimer's Disease (TRAP-AD)

Inclusion Criteria:

1. Able to give written informed consent and follow study procedures.

2. Age > or = 65 years and < or = 85 years.

3. Meets the Petersen MCI criteria for Amnestic MCI (single and multiple domain) with aClinical Dementia Rating (CDR) between 0.5-1.0, and a Functional Assessment Staging (FAST) of 1-4.

4. Be willing to identify an informed relative, family member, spouse, or friend forstudy staff to interview to confirm subject reports as per UDS 3.0 guidelines;however the lack of a study informant is not exclusionary.

5. Have at least a high school diploma/12 years of education.

6. Participants with current mild MDD may be allowed to participate, given that mildMDD does not affect cognition and does not pose increased risk to the participant,as determined by site PI on a case-by-case basis.

Exclusion Criteria:

1. Unwilling/unable to comply with study procedures.

2. Other diagnosis of dementia (i.e. not Alzheimer's type), history of brain tumor, MRIevidence of brain damage or brain disease including significant trauma,hydrocephalus, seizures, intellectual disability, or other serious neurologicaldisorder (e.g. Parkinson's disease or other movement disorders).

3. History of significant cerebrovascular pathology (e.g., significant stroke).Subjects with a history of cardiovascular disease (e.g., myocardial infarction) willbe allowed to participate at site PI's discretion, on a case-by-case basis, giventhat the cardiovascular disease is stable and does not reflect the presence ofsignificant cerebrovascular pathology.

4. Clinically unstable systemic medical disorders.

5. Current DSM-5 diagnosis of alcohol or drug use disorder or other major psychiatricillness (e.g., schizophrenia, bipolar, PTSD, depression). Participants with currentmild MDD may be allowed to participate, given that mild MDD does not affectcognition and does not pose increased risk to the participant, as determined by sitePI on a case-by-case basis. Participants with current moderate/severe MDD will beexcluded.

6. Clinical or laboratory evidence of hypothyroidism.

7. Clinically significant abnormal findings of laboratory parameters or at physicalexamination.

8. Medications affecting cognition (e.g., narcotic analgesics; chronic use ofmedications with anticholinergic activity, anti-Parkinsonian medications,antipsychotic meds, etc.). Stable use (i.e., = 6 months) of memantine oracetylcholinesterase inhibitors will be allowed.

9. Family history of early onset (<60 y/o) dementia.

10. Past intolerance or hypersensitivity to t-PBM.

11. Significant skin conditions on the subject's scalp in the area of the proceduresites.

12. Any use of light-activated drugs (photodynamic therapy) within 14 days prior tostudy enrollment.

13. Any type of implants in the head, whose functioning might be affected by t-PBM.

14. The completion of study imaging procedures is highly encouraged, but not mandatoryfor participants with extenuating circumstances (e.g., having prosthetic devices ormetallic foreign bodies that constitute hazards for MRI, unable to get PET due toprevious level of radiation exposure, having claustrophobia, having a large bodysize and shape).