Transcranial Photobiomodulation to Improve Cognition in Gulf War Illness

Modifying Alzheimer's disease pathophysiology with photobiomodulation: model, evidence, and future with EEG-guided intervention

This manuscript outlines a model of Alzheimer's Disease (AD) pathophysiology in progressive layers, from its genesis to the development of biomarkers and then to symptom expression. Genetic predispositions are the major factor that leads to mitochondrial dysfunction and subsequent amyloid and tau protein accumulation, which have been identified as hallmarks of AD. Extending beyond these accumulations, we explore a broader spectrum of pathophysiological aspects, including the blood-brain barrier, blood flow, vascular health, gut-brain microbiodata, glymphatic flow, metabolic syndrome, energy deficit, oxidative stress, calcium overload, inflammation, neuronal and synaptic loss, brain matter atrophy, and reduced growth factors. Photobiomodulation (PBM), which delivers near-infrared light to selected brain regions using portable devices, is introduced as a therapeutic approach. PBM has the potential to address each of these pathophysiological aspects, with data provided by various studies. They provide mechanistic support for largely small published clinical studies that demonstrate improvements in memory and cognition. They inform of PBM's potential to treat AD pending validation by large randomized controlled studies. The presentation of brain network and waveform changes on electroencephalography (EEG) provide the opportunity to use these data as a guide for the application of various PBM parameters to improve outcomes. These parameters include wavelength, power density, treatment duration, LED positioning, and pulse frequency. Pulsing at specific frequencies has been found to influence the expression of waveforms and modifications of brain networks. The expression stems from the modulation of cellular and protein structures as revealed in recent studies. These findings provide an EEG-based guide for the use of artificial intelligence to personalize AD treatment through EEG data feedback.

The Effect of Intranasal Plus Transcranial Photobiomodulation on Neuromuscular Control in Individuals with Repetitive Head Acceleration Events

Objective: This proof-of-concept study was to investigate the relationship between photobiomodulation (PBM) and neuromuscular control. Background: The effects of concussion and repetitive head acceleration events (RHAEs) are associated with decreased motor control and balance. Simultaneous intranasal and transcranial PBM (itPBM) is emerging as a possible treatment for cognitive and psychological sequelae of brain injury with evidence of remote effects on other body systems. Methods: In total, 43 (39 male) participants, age 18-69 years (mean, 49.5; SD, 14.45), with a self-reported history of concussive and/or RHAE and complaints of their related effects (e.g., mood dysregulation, impaired cognition, and poor sleep quality), completed baseline and posttreatment motor assessments including clinical reaction time, grip strength, grooved pegboard, and the Mini Balance Evaluation Systems Test (MiniBEST). In the 8-week interim, participants self-administered itPBM treatments by wearing a headset comprising four near-infrared light-emitting diodes (LED) and a near-infrared LED nasal clip. Results: Posttreatment group averages in reaction time, MiniBEST reactive control subscores, and bilateral grip strength significantly improved with effect sizes of g = 0.75, g = 0.63, g = 0.22 (dominant hand), and g = 0.34 (nondominant hand), respectively. Conclusion: This study provides a framework for more robust studies and suggests that itPBM may serve as a noninvasive solution for improved neuromuscular health.

From functional neuroimaging to neurostimulation: fNIRS devices as cognitive enhancers

Functional near-infrared spectroscopy (fNIRS) relies on near-infrared (NIR) light for changes in tissue oxygenation. For decades, this technique has been used in neuroscience to measure cortical activity. However, recent research suggests that NIR light directed to neural populations can modulate their activity through "photobiomodulation" (PBM). Yet, fNIRS is being used exclusively as a measurement tool. By adopting cognitive tests sensitive to prefrontal functioning, we show that a 'classical' fNIRS device, placed in correspondence of the prefrontal cortices of healthy participants, induces faster RTs and better accuracy in some of the indexes considered. A well-matched control group, wearing the same but inactive device, did not show any improvement. Hence, our findings indicate that the 'standard' use of fNIRS devices generates PBM impacting cognition. The neuromodulatory power intrinsic in that technique has been so far completely overlooked, and future studies will need to take this into account.

Dose response of transcranial near infrared light stimulation on brain functional connectivity and cognition in older adults-A randomized comparison

Photobiomodulation, also called low-level light therapy, has been reported in animal studies to have an effect on brain activity and cognition. However, studies in humans regarding its effect on cognition and brain functional connectivity, and the required dose threshold for achieving the same have been very limited. We compared the effects of different doses of photobiomodulation (PBM) on cognition and resting state brain functional connectivity in 25 cognitively normal adults aged 55-70 years. They were randomized to a single session of the sham group, "low-dose" and "high-dose" groups receiving NIR light with transcranial fluence of 26 and 52 J/cm2 respectively, and intranasal fluence of 9 and 18 J/cm2 respectively. There was a significant increase in resting state functional connectivity of the left superior frontal gyrus (SFG) with the left planum temporale (PT), p = 0.0016, and with the left inferior frontal gyrus, pars triangularis, p = 0.0235 in the "high-dose" group only compared to the "sham" group. There was also a significant improvement in visual search and processing speed (p = 0.012) in the "high-dose" group. Replication of these findings in an adequately powered randomized sham-controlled study in healthy older adults can pave the way for clinical application of NIRL as a therapeutic modality in patients with Alzheimer's disease.

Pulsed transcranial photobiomodulation generates distinct beneficial neurocognitive effects compared with continuous wave transcranial light

Previous research has demonstrated the beneficial effect brought by transcranial photobiomodulation (tPBM). The present study is a further investigation of pulsed transcranial light delivery, from the perspective of wavelength, operation mode, and pulse frequency. A total of 56 healthy young adults (28 males and 28 females) were included in this randomized, sham-controlled experimental study. The wavelength of tPBM was 660 nm and 850 nm, and under each wavelength, subjects were randomly assigned to one of the following four treatments: (1) sham control; (2) continuous-wave (CW) tPBM; (3) pulsed-wave (PW) tPBM (40 Hz); and (4) PW tPBM (100 Hz). The tPBM duration was 8 min and the mean power density was fixed at 250 mW/cm2. Karolinska Sleepiness Scale (KSS) questionnaire, psychomotor vigilance task (PVT), and delayed match-to-sample (DMS) task were completed by subjects before and after the intervention to test whether PW tPBM produced distinct beneficial effects with measures of sleepiness, attention, and memory. 32-channel electroencephalography (EEG) signals were obtained from subjects before, during and after receiving tPBM or sham intervention. Paired sample T test showed that the KSS score, the number of correct responses of PVT, and DMS rate correct score (RCS) of PW tPBM groups improved significantly after intervention (p < 0.05). With regard to EEG analysis, paired one-way repeated ANOVA test showed that during the intervention of PW tPBM, the average power within the Gamma band was higher than the baseline (p < 0.05). Our study presented that PW tPBM could generate better beneficial cognitive effects and change brain electrical activity under certain circumstances.

Use of either transcranial or whole-body photobiomodulation treatments improves COVID-19 brain fog

There is increasing recognition of post-COVID-19 sequelae involving chronic fatigue and brain fog, for which photobiomodulation (PBM) therapy has been utilized. This open-label, pilot, human clinical study examined the efficacy of two PBM devices, for example, a helmet (1070 nm) for transcranial (tPBM) and a light bed (660 and 850 nm) for whole body (wbPBM), over a 4-week period, with 12 treatments for two separate groups (n = 7 per group). Subjects were evaluated with a neuropsychological test battery, including the Montreal Cognitive Assessment (MoCA), the digit symbol substitution test (DSST), the trail-making tests A and B, the physical reaction time (PRT), and a quantitative electroencephalography system (WAVi), both pre- and post- the treatment series. Each device for PBM delivery was associated with significant improvements in cognitive tests (p < 0.05 and beyond). Changes in WAVi supported the findings. This study outlines the benefits of utilizing PBM therapy (transcranial or whole-body) to help treat long-COVID brain fog.

Transcranial Photobiomodulation Treatment: Significant Improvements in Four Ex-Football Players with Possible Chronic Traumatic Encephalopathy

Background

Chronic traumatic encephalopathy, diagnosed postmortem (hyperphosphorylated tau), is preceded by traumatic encephalopathy syndrome with worsening cognition and behavior/mood disturbances, over years. Transcranial photobiomodulation (tPBM) may promote improvements by increasing ATP in compromised/stressed cells and increasing local blood, lymphatic vessel vasodilation.

Objective

Aim 1: Examine cognition, behavior/mood changes Post-tPBM. Aim 2: MRI changes - resting-state functional-connectivity MRI: salience, central executive, default mode networks (SN, CEN, DMN); magnetic resonance spectroscopy, cingulate cortex.

Methods

Four ex-players with traumatic encephalopathy syndrome/possible chronic traumatic encephalopathy, playing 11- 16 years, received In-office, red/near-infrared tPBM to scalp, 3x/week for 6 weeks. Two had cavum septum pellucidum.

Results

The three younger cases (ages 55, 57, 65) improved 2 SD (p < 0.05) on three to six neuropsychological tests/subtests at 1 week or 1 month Post-tPBM, compared to Pre-Treatment, while the older case (age 74) improved by 1.5 SD on three tests. There was significant improvement at 1 month on post-traumatic stress disorder (PTSD), depression, pain, and sleep. One case discontinued narcotic pain medications and had reduced tinnitus. The possible placebo effect is unknown. At 2 months Post-tPBM, two cases regressed. Then, home tPBM was applied to only cortical nodes, DMN (12 weeks); again, significant improvements were seen. Significant correlations for increased SN functional connectivity (FC) over time, with executive function, attention, PTSD, pain, and sleep; and CEN FC, with verbal learning/memory, depression. Increased n-acetyl-aspartate (NAA) (oxygen consumption, mitochondria) was present in anterior cingulate cortex (ACC), parallel to less pain and PTSD.

Conclusion

After tPBM, these ex-football players improved. Significant correlations of increased SN FC and CEN FC with specific cognitive tests and behavior/mood ratings, plus increased NAA in ACC support beneficial effects from tPBM.

Can transcranial photobiomodulation improve cognitive function? A systematic review of human studies

BACKGROUND

Transcranial photobiomodulation (tPBM) has been studied for over a decade as a possible cognitive intervention.

OBJECTIVE

To evaluate the effect of tPBM for enhancing human cognitive function in healthy adults and remediating impaired cognitive function in adults with cognitive disorders.

METHODS

A systematic literature search from three electronic databases (PubMed, Scopus, Web of Science) was conducted from 1987 to May 2022. The cognitive function being evaluated included learning and memory, attention, executive function, language, and global cognitive function.

RESULTS

Of the 35 studies identified, 29 (82.9 %) studies reported positive improvement in cognitive functions after tPBM. All nine studies on participants with subjective memory complaints, mild cognitive impairment, and dementia, showed positive outcomes. Seven (87.5 %) studies on traumatic brain injury (TBI) patients also showed positive results. A series of clinical trials on stroke patients showed positive trends on improved neurological deficit at first, but was prematurely terminated later at phase III due to the lack of statistical significance. One of the most common protocols for clinical populations employed devices delivering near-infrared light (810 nm), the irradiance of 20-25 mW/cm², and fluence of 1-10 J/cm². While this was common, the reviewed protocols also included other wavelengths of light ranging from visible, red (630-635 nm) to invisible near-infrared maximum wavelengths of 1060-1068 nm.

CONCLUSIONS

tPBM seems to improve cognitive function. However, only half of the reviewed clinical trials were randomized control trials, further investigation is warranted.

No Effects of Photobiomodulation on Prefrontal Cortex and Hippocampal Cytochrome C Oxidase Activity and Expression of c-Fos Protein of Young Male and Female Rats

The role of light in our biological processes and systems is extensively known. In addition, the use of light devices has been introduced in the field of healthcare as an opportunity to administer power light at specific wavelengths to improve our body functions and counteract light deficiency. One of these techniques is photobiomodulation (PBM), which uses red to infrared light in a non-invasive way to stimulate, heal, regenerate, and protect tissue. The main proposed mechanism of action is the stimulation of the cytochrome c oxidase (CCO), the terminal enzyme in the mitochondrial electron transport chain. PBM has achieved positive effects on brain activity and behavioral function of several adult animal models of health and disease, the potential use of this technique in developing stages is not surprising. This research aims to examine the effects of PBM on the prefrontal cortex and hippocampus of 23 day-old healthy male (n = 31) and female (n = 30) Wistar rats. Three groups of each sex were used: a PBM group which received 5 days of PBM, a device group submitted to the same conditions but without light radiation, and a control basal group. CCO histochemistry and c-Fos immunostaining were used to analyze brain metabolic activity and immediate early genes activation, respectively. Results displayed no metabolic differences between the three groups in both sexes. The same results were found in the analysis of c-Fos positive cells, reporting no differences between groups. This research, in contrast to the PBM consequences reported in healthy adult subjects, showed a lack of PBM effects in the brain markers we examined in young healthy rat brains. At this stage, brain function, specifically brain mitochondrial function, is not disturbed so it could be that the action of PBM in the mitochondria may not be detectable using the analysis of CCO activity and c-Fos protein expression. Further studies are needed to examine in depth the effects of PBM in brain development, cognitive functions and postnatal disorders, along with the exploration of the optimal light parameters.