Transcranial photobiomodulation (tPBM) is a novel, non-invasive neurostimulation technique, which has shown compelling potential for cognitive improvement. Increasing neuroimaging studies have demonstrated that functional brain network models would sensitively and comprehensively delineate action mechanisms of multiple neurostimulation techniques. However, the action mechanism of tPBM based on functional brain network remain largely unknown. In this project, the investigators aim to investigate the effectiveness of tPBM on working memory for healthy older adults. Taking the randomized, single-blind controlled method, participants in the active tPBM group will take active tPBM, and those in the sham tPBM group will take sham tPBM. After that, the investigators will investigate the changes of working. Furthermore, based on the neuroimaging technique, the regulatory mechanism of tPBM in intervening older adults will be revealed from the perspective of altered brain functional networks. This study will provide evidence for understanding whether the tPBM has the potentially therapeutic effect on cognitive function for healthy older adults as a non-drug treatment, and further elucidating the potential brain mechanism, which are of great values in solving scientific and clinical practice issues.

An astonishing rise in the prevalence of cognitive decline and dementia in older adults was witnessed in recent years, which renders investigations of cognitive intervention especially urgent and vital. Transcranial photobiomodulation (tPBM) is now considered as a potentially non-pharmacologic intervention for cognitive decline and has attracted the interest of researchers. However, there are few existing studies involving the mechanism of tPBM on brain functional networks.

Sixty healthy older participants will be recruited in this randomized, single-blind controlled trial. Each group had thirty participants.Participants in the active tPBM group will take active tPBM and those in the sham tPBM group will take sham tPBM. After that, the investigators will investigate the changes of working memory, which is the primary outcome. Furthermore, based on the neuroimaging technique of functional near-infrared spectroscopy (fNIRS), the regulatory mechanism of tPBM in intervening older adults will be revealed from the perspective of altered brain functional networks.

This study will provide evidence for understanding whether the tPBM has the potentially therapeutic effect on cognitive function for healthy older adults as a non-drug treatment, and further elucidating the potential brain mechanism, which are of great values in solving scientific and clinical practice issues.

Inclusion Criteria:

• 50-79 years old, right-handed and Mandarin-speaking subjects;
• Normal age-adjusted, gender-adjusted and education-adjusted performance on standardised cognitive tests

Exclusion Criteria:

• Current diagnosis with mild cognitive decline or dementia;
• Current major psychiatric diagnoses such as severe depression and anxiety;
• Other neurological conditions (e.g., cerebrovascular disease, brain tumors, Parkinson's disease, encephalitis, or epilepsy)
• Other diseases which could cause cognitive decline (e.g., thyroid dysfunction, severe anemia, syphilis, or HIV)

The information of neuropsychological tests will be shared with other researchers.

When summary data are published or starting 6 months after publication

The information of neuropsychological tests data will be shared.