Effects of stimulating frequency of NIR LEDs light irradiation on forehead as quantified by EEG measurements

Abstract

Near-infrared (NIR) light has been shown to produce a range of physiological effects in humans, however, there is still no agreement on whether and how a single parameter, like the flicker frequency of NIR light, affects the brain. Methods: An 810[Formula: see text]nm NIR LED was used as the stimulator. Fifty subjects participated in this experiment. Forty subjects were randomly divided into four groups. Each group underwent a 30-minute NIR LED radiation with four different frequencies (i.e., 0[Formula: see text]Hz, 5[Formula: see text]Hz, 10[Formula: see text]Hz and 20[Formula: see text]Hz, respectively) on the forehead. The remaining 10 subjects formed the control group, in which they underwent a 30-minute rest period without light radiation. EEG signals of all subjects during each test were recorded. Gravity frequency (GF), relative energy change, and sample entropy were analyzed. Results: The experimental groups had larger GF values compared to the control group. Higher stimulation frequency would cause larger growth of GF ([Formula: see text], [Formula: see text]). The amplitude of alpha waves relative energy increased, while theta waves decreased remarkably in the experimental groups ([Formula: see text]), and the extent of increase/decrease was larger at higher stimulation frequency, compared to that of the control. Sample entropy of electrodes in the frontal areas were much larger than those in other brain areas in the experimental groups ([Formula: see text]). Conclusions: Larger frequency of the NIR LED light would cause more distinct brain activities in the stimulated areas. It indicates that NIR LED light may have a positive effect on modulating brain activity. These results may help improve the design of photobiomodulation treatments in the future.

Combination of Group Singular Value Decomposition and eLORETA Identifies Human EEG Networks and Responses to Transcranial Photobiomodulation

“…Significant modulation effects displayed a network-dependent manner with significantly enhanced alpha power at SVD networks 1 (pDMN), 4 (left-FPN), 6 (ECN), and 8 (lateral visual network; LVN) throughout the during and post-tPBM period while SVD networks 2, 5, 9 were boosted only in the last 4 min of tPBM. According to previous reports by other research groups and ours, alpha power enhancement has been consistently observed as a main effect of tPBM ( Wang et al, 2019 , 2021 ; Zomorrodi et al, 2019 ; Yao et al, 2020 ). This consistent observation demonstrates the reproducibility of the tPBM effects in the human brains.…”

Devices used for photobiomodulation of the brain—a comprehensive and systematic review

“…of articles No. of subjects Condition of subjects Age Sex Sham controlled Treatment time Outcomes measured Results Physiological characterisation [ 9 – 13 , 39 , 42 , 43 , 47 , 52 , 53 , 65 , 66 , 69 , 72 , 76 , 79 , 86 , 90 , 91 , 102 ] 21 553 552 healthy volunteers. 1 patient 18–85 years 256 females.…”

“…Regarding stimulus location, the PFC is the most commonly stimulated region of the brain, with some articles mentioning the lack of hair in the forehead, and therefore, higher light penetration [ 39 , 66 , 76 ]. However, a substantial number of studies (e.g., those which used helmet devices) stimulated the scalp with hair and also showed beneficial outcomes, which means that the effect of hair in light penetration in head structures should be further investigated to understand if it has a significant effect.…”

“…One article assessing the effect of PBM in cortical excitability studied the use of pulsed NIR light in the 5 Hz, 10 Hz and 20 Hz frequencies, with a 50% duty cycle. This study noticed that not only low energy NIR stimulation changed the EEG signal when compared to the control group, but also that increasing frequency had a greater impact on brain activity, which may have a role in the improvement of memory [ 76 ].…”

Protocol for randomized controlled trial to evaluate the safety and feasibility of a novel helmet to deliver transcranial light emitting diodes photobiomodulation therapy to patients with Parkinson’s disease

“…Specifically, the effect of transcranial LED’s on brain function has been well-studied with changes to various parameters noted in animal models and humans ( Shaw et al, 2010 ; Naeser and Hamblin, 2011 ; Jahan et al, 2019 ; Zomorrodi et al, 2019 ; Longo et al, 2020 ; El Khoury et al, 2021 ; Yao et al, 2021 ). The effects reported in human studies include increased activity in areas associated with attention and novelty ( El Khoury et al, 2021 ), beneficial effects in attentional performance ( Jahan et al, 2019 ), positive effects on modulating brain activity ( Yao et al, 2021 ), increased organization of neural function ( Zomorrodi et al, 2019 ) and a beneficial effect on myelin repair pathways ( Longo et al, 2020 ).…”