The aim of this study is to better understand the effects of transcranial photobiomodulation (tPBM) on neural oscillations of individuals diagnosed with Down syndrome.

This study will compare the effect of tPBM to sham tPBM on gamma neural oscillations in the brain as assessed by EEG, and on language, attention and memory as assessed by neuropsychological testing. Participants will be randomized to either tPBM with near-infrared light (tPBM-NIR) or tPBM-Sham and will undergo 18 treatments (3 treatments per week for 6 weeks) in addition to baseline, short-term and long- term follow up visits.

Inclusion criteria for this study include:

1. adult men and women between the ages of 16 and 35
2. diagnosis of DS (i.e., clinical diagnosis of Trisomy 21 or Complete Unbalanced Translocation of Chromosome 21)

Exclusion criteria for this study include:

1. diagnosis of seizure disorder
2. diagnosis of dementia
3. inability to complete study procedures
4. English as a second language
5. speech as the secondary mode of communication
6. speech of less than two-word utterances
7. changes in medications, augmentative devices, and other intervention two weeks prior to baseline testing and throughout study completion at PI's discretion
8. untreated obstructive sleep apnea (OSA)
9. Participation in other clinical research trials that may influence affect primary outcomes or adherence to the proposed study, as assessed by the PI and the Co-Is
10. candidates who have a current diagnosis of cancer and/or are currently undergoing treatment for cancer
11. history of migraine with an aura in the past 6 months
12. current pregnancy