The goal of this pilot clinical trial is to test whether transcranial photobiomodulation (tPBM), a non-invasive brain stimulation technique using near-infrared light, can improve brain blood flow regulation (neurovascular coupling) and cognitive function in older adults.
The main questions it aims to answer are:
* Does tPBM enhance neurovascular coupling responses during memory and finger tapping tasks? * Are these improvements linked to better cognitive performance and lower levels of brain inflammation and oxidative stress?
Researchers will compare an active tPBM treatment arm to a sham treatment arm to see if tPBM leads to measurable improvements in brain activity and cognitive function compared to no active stimulation.
Participants will:
* Receive either active tPBM or sham stimulation sessions for 4 weeks, every other day using a portable intervention device. * Complete questionnaires and an iPAD-based cognitive testing protocol * Complete memory and motor tasks while their brain activity is measured using non-invasive techniques: simultaneous functional near-infrared spectroscopy (fNIRS) and electroencephalography (EEG), transcranial doppler (TCD) flowmetry. * Retinal vessel reactivity will be measured during flickering light stimulus using a special camera (dynamic vessel analysis, DVA). * Provide blood samples to test for biomarkers of inflammation, oxidative stress and brain cell damage.
Age: 21-85 years of age
Adequate hearing and visual acuity to participate in the examinations
Ability to read and write in English
Competence to provide informed consent
Active CNS disease including multiple sclerosis, uncontrolled seizures, active brain cancer
Cerebrovascular accident other than TIA within 60 days prior to Visit 0
Major psychiatric disease, including major depression not currently controlled on medications, alcohol or drug abuse
Participant currently uses commercial brain stimulation / neuromodulation device or an experimental device as part of a research study, e.g. tDCS, tACS, TBS, DBS, TMS, TPBM, etc.
Parallel
transcranial photobiomodulation
DeviceThe Vielight Neuro Gamma TPBM devices (©Vielight Inc.) will be used to transmit pulsed near-infrared (NIR) energy through the cranium. Device emits NIR photons at 810 m wavelength generating \~100 mW/cm2 pulsed NIR power modulated at 40 Hz frequency. The six NIR light sources are positioned along the midline over the frontal, pariatel and occipital cortices, bilaterally over the temporal cortex, and intranasally. Due to its portable design, Vielight Neuro TBPM instruments can be used in the laboratory, bedside, or at the participant's home. Active / sham photobiomodulation sessions last for 20 minutes and will be administered at a laboratory-, home-, or office-based setting depending on the preference of the participant. TPBM will be performed three or four times a week for four weeks, maximum once every other day. Participants will complete a questionnaire of adverse events after each photobiomodulation session.
Cognitive performance
Cognitive performance will be assessed by using the following batteries of the NIH Toolbox: 1) Dimensional Change Card Sort \[executive function\]; 2) Pattern Comparison Processing Speed; 3) List Sorting Working Memory; 4) Flanker Inhibitory Control and Attention; 5) Picture Sequencing Memory and/or 6) Oral Symbol Digit Test.
Neurovascular coupling response
Neuronal stimulus-induced cerebral hemodynamic response measured in the brain cortex using functional near-infrared spectroscopy, during a cognitive or motor paradigm. Increase in blood flow velocity recorded from the middle cerebral artery during cognitive n-back paradigm using transcranial Doppler (TCD) flowmetry.
Brain wave power
Band limited power in delta-, theta-, alpha-, beta- and gamma-bands during resting and task state measured by electroencephalography (EEG)
Functional connectivity
Correlation of simultaneously recorded cerebral hemodynamics (by fNIRS) or phase synchronization of simultaneously recorded cortical potential changes (by EEG).
Retinal vasoreactivity
Flickering light induced change in diameter of retinal arterioles and venules assessed by dynamic vessel analysis.
Cerebrovascular endothelium-derived extracellular vesicles
Extracellular vesicles of cerebrovascular endothelial origin will be isolated from platelet poor plasma obtained from the participant and their count will be determined reflecting the health of brain vessels.
Pro-inflammatory cytokines
The following pro-inflammatory cytokines will be determined from participant's serum: Interleukin-1β, Interleukin-6, Interleukin-8 and Tumor Necrosis Factor-α
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