Transcranial laser stimulation: Mitochondrial and cerebrovascular effects in younger and older healthy adults.
Level 2 - randomized trial
Randomized sham-controlled trial in humans
PubMed 33636401 · doi:10.1016/j.brs.2021.02.011
What was done
In a randomized, sham-controlled study, 68 healthy adults aged 18–85 received either 1064-nm transcranial laser stimulation (area: 13.6 cm², power density: 250 mW/cm²) or sham stimulation delivered to the right anterior prefrontal cortex (Brodmann Area 10). Broadband near-infrared spectroscopy was used to measure bilateral cortical changes in oxidized cytochrome-c-oxidase and hemoglobin oxygenation (oxygenated and deoxygenated hemoglobin) before, during, and after stimulation.
What was found
The abstract reports directional statistical significance without exact numbers, effect sizes, or p-values. Compared with sham, active laser stimulation produced a significant increase in oxidized cytochrome-c-oxidase during stimulation, followed by a significant post-stimulation increase in oxygenated hemoglobin and a decrease in deoxygenated hemoglobin. The laser effect on cytochrome-c-oxidase was greater with increasing age, whereas the cerebral hemodynamic response decreased with increasing age. No adverse effects were reported.
Why it matters
This study provides in vivo human evidence that noninvasive near-infrared laser stimulation can acutely modulate cortical mitochondrial respiration and cerebral oxygenation, with older adults showing greater mitochondrial target engagement.
Limits
The abstract provides no numerical data, confidence intervals, or exact p-values. Only acute physiological markers were measured during and immediately after a single session, without cognitive, functional, or long-term clinical outcomes. The sample was restricted to healthy adults.
Cited by
- supports Infrared and red light can penetrate biological tissue, including hair and the skull, into the brain, where mitochondrial cytochrome c oxidase acts as the photoreceptor absorbing photons.