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Performance on 2-back task (n = 6): accuracy in target detection (%) and number of false positives (#) before and after tPBM with continuous light.

Performance on 2-back task (n = 6): accuracy in target detection (%) and number of false positives (#) before and after tPBM with continuous light.

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Article
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Background: Transcranial photobiomodulation (tPBM) has recently emerged as a potential cognitive enhancement technique and clinical treatment for various neuropsychiatric and neurodegenerative disorders by delivering invisible near-infrared light to the scalp and increasing energy metabolism in the brain. Objective: We assessed whether transcran...

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... Thus, the reduction in this metric could be attributed to a significant reduction in global integration (as reflected by a reduction in GE) and/or a significant increase in global segregation of the brain network caused by tPBM. These observed significant effects of tPBM on SW taking place only in Stim2 could result from the resistance of resting-state networks against changes in network composition as well as the dose-dependent nature of tPBM-induced effects on neural activity [89,90]. However, a possible explanation for the lack of significant alterations in synchronization and GE in Stim2 could be the high variability in the functional topography of the frontoparietal network [78]. ...
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Objective: Transcranial photobiomodulation (tPBM) has shown promising benefits, including cognitive improvement, in healthy humans and in patients with Alzheimer's disease. In this study, we aimed to identify key cortical regions that present significant changes caused by tPBM in the electroencephalogram (EEG) oscillation powers and functional connectivity in the healthy human brain. Approach: A 64-channel EEG was recorded from 45 healthy participants during a 13-min period consisting of a 2-min baseline, 8-min tPBM/sham intervention, and 3-min recovery. After pre-processing and normalizing the EEG data at the five EEG rhythms, cluster-based permutation tests were performed for multiple comparisons of spectral power topographies, followed by graph-theory analysis (GTA) as a topological approach for quantification of brain connectivity metrics at global and nodal/cluster levels. Main results: EEG power enhancement was observed in clusters of channels over the frontoparietal regions in the alpha band and the centroparietal regions in the beta band. The global measures of the network revealed a reduction in synchronization, global efficiency, and small-worldness of beta band connectivity, implying an enhancement of brain network complexity. In addition, in the beta band, nodal graphical analysis demonstrated significant increases in local information integration and centrality over the frontal clusters, accompanied by a decrease in segregation over the bilateral frontal, left parietal, and left occipital regions. Significance: Frontal tPBM increased EEG alpha and beta powers in the frontal-central-parietal regions, enhanced the complexity of the global beta-wave brain network, and augmented local information flow and integration of beta oscillations across prefrontal cortical regions. This study sheds light on the potential link between electrophysiological effects and human cognitive improvement induced by tPBM.
... In patients suffering from either chronic stroke or Alzheimer's disease, both of which have abnormally functioning networks, photobiomodulation could strengthen and influence functional connectivity within the default mode network itself, together with its connectivity with other networks, for example the salience and central executive networks (Chao, 2019;Naeser et al., 2019). In essence, in these damaged and/or diseased states, photobiomodulation may help correct the imbalance of functional connectivity, restoring the connectivity between cortical areas to "normal" levels (Saltmarche et al., 2017;Chao, 2019;Naeser et al., 2019;Zomorrodi et al., 2019;Spera et al., 2021). These improvements in functional connectivity manifest in improvements in cognition and memory in, for example, Alzheimer's disease patients (Lim, 2014;Berman et al., 2017;Saltmarche et al., 2017;Chao, 2019;Baik et al., 2021). ...
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Over the last seventy years or so, many previous studies have shown that photobiomodulation, the use of red to near infrared light on body tissues, can improve central and peripheral neuronal function and survival in both health and in disease. These improvements are thought to arise principally from an impact of photobiomodulation on mitochondrial and non-mitochondrial mechanisms in a range of different cell types, including neurones. This impact has downstream effects on many stimulatory and protective genes. An often-neglected feature of nearly all of these improvements is that they have been induced during the state of wakefulness. Recent studies have shown that when applied during the state of sleep, photobiomodulation can also be of benefit, but in a different way, by improving the flow of cerebrospinal fluid and the clearance of toxic waste-products from the brain. In this review, we consider the potential differential effects of photobiomodulation dependent on the state of arousal. We speculate that the effects of photobiomodulation is on different cells and systems depending on whether it is applied during wakefulness or sleep, that it may follow a circadian rhythm. We speculate further that the arousal-dependent photobiomodulation effects are mediated principally through a biophoton – ultra-weak light emission – network of communication and repair across the brain.
... tPBM has been consistently reported to shift brain oscillations to higher frequency bands, at least in healthy subjects. Our group reported on the potentiation of gamma and beta power after tPBM [97]. ...
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Sexual dysfunction (SD) is frequently encountered in patients suffering from depression. There is a bidirectional relationship between various types of SD and depression, so the presence or treatment of one condition may exacerbate or improve the other condition. The most frequent sexual problem in untreated depressed patients is declining sexual desire, while in treated depressed patients it is difficulties with erection/ejaculation and with orgasm. Numerous classes of neuropsychiatric medications, commonly used in depressed patients—such as antidepressant, antipsychotic, alpha sympathetic, and opioid drugs—may cause SD. Photobiomodulation (PBM) therapy, also called low-level light/laser therapy, is a novel neuromodulation technique for neuropsychiatric conditions, such as depression. Transcranial PBM (tPBM) targets the cellular metabolism—through the mitochondrial respiratory enzyme, cytochrome c oxidase—and has numerous cellular and physiological beneficial effects on the central nervous system. This paper represents a comprehensive review of the application of tPBM to SD, coexisting with depression or induced by antidepressant medications.
... However, research on the mechanism of tPBM-evoked electrophysiological effects in the human brain is on its early stage with only a handful of publications (Berman et al., 2017;Vargas et al., 2017;Zomorrodi et al., 2019;Ghaderi et al., 2021;Spera et al., 2021), besides ours , in the last 4-5 years. Most of these studies have reported alterations of electroencephalography (EEG) powers by tPBM compared to sham stimulation. ...
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Transcranial Photobiomodulation (tPBM) has demonstrated its ability to alter electrophysiological activity in the human brain. However, it is unclear how tPBM modulates brain electroencephalogram (EEG) networks and is related to human cognition. In this study, we recorded 64-channel EEG from 44 healthy humans before, during, and after 8-min, right-forehead, 1,064-nm tPBM or sham stimulation with an irradiance of 257 mW/cm2. In data processing, a novel methodology by combining group singular value decomposition (gSVD) with the exact low-resolution brain electromagnetic tomography (eLORETA) was implemented and performed on the 64-channel noise-free EEG time series. The gSVD+eLORETA algorithm produced 11 gSVD-derived principal components (PCs) projected in the 2D sensor and 3D source domain/space. These 11 PCs took more than 70% weight of the entire EEG signals and were justified as 11 EEG brain networks. Finally, baseline-normalized power changes of each EEG brain network in each EEG frequency band (delta, theta, alpha, beta and gamma) were quantified during the first 4-min, second 4-min, and post tPBM/sham periods, followed by comparisons of frequency-specific power changes between tPBM and sham conditions. Our results showed that tPBM-induced increases in alpha powers occurred at default mode network, executive control network, frontal parietal network and lateral visual network. Moreover, the ability to decompose EEG signals into individual, independent brain networks facilitated to better visualize significant decreases in gamma power by tPBM. Many similarities were found between the cortical locations of SVD-revealed EEG networks and fMRI-identified resting-state networks. This consistency may shed light on mechanistic associations between tPBM-modulated brain networks and improved cognition outcomes.
... [38,39] Spera et al. delivered laser treatment through an arterial catheter leading into the brain and found that the laser reduced the score for dementia in AD patients. [40] In the only study of patients with PD, which was noncontrolled and nonrandomized, motor and cognitive functions improved after PBM treatment. [41] In patients with TBI, NIR laser treatment significantly decreased the signs of headache and improved sleep quality and cognitive and mood states. ...
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Photobiomodulation (PBM) therapy is a therapeutic method that can produce a range of physiological effects in cells and tissues using certain wavelengths. The reparative benefits of PBM therapy include wound healing, bone regeneration, pain reduction, and the mitigation of inflammation. Advances in the development of laser instruments, including the use of high-intensity lasers in physiotherapy, have recently led to controllable photothermal and photomechanical treatments that enable therapeutic effects to be obtained without damaging tissue. The combination of PBM therapy with acupuncture may provide new perspectives for investigating the underlying therapeutic mechanisms of acupuncture and promote its widespread application.
... Functional near-infrared spectroscopy showed that the hemodynamic responses during the memory tasks were lower after PBM. Another paper from Cassano's group used transcranial PBM to modify electroencephalogram activity and cerebral blood flow [14]. c-tPBM significantly boosted gamma and beta EEG spectral power in eyesopen recording and gamma power in eyes-closed recording. ...
Article
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.
Article
Background: Recent innovative non-pharmacological interventions and neurostimulation devices have shown potential for application in the treatment of Alzheimer's disease (AD). These include photobiomodulation (PBM) therapy. Objective: This pilot study assesses the safety, compliance with, and efficacy of a brain-gut PBM therapy for mild-to-moderate AD patients. Methods: This double-blind, randomized, monocentric sham-controlled study started in 2018 and ended prematurely in 2020 due to the COVID-19 pandemic. Fifty-three mild-to-moderate AD patients were randomized, 27 in the PBM group and 26 in the sham group. All patients had 40 treatment sessions lasting 25 min each over 8 weeks and were followed for 4 weeks afterwards. Compliance with the treatment was recorded. Safety was assessed by recording adverse events (AEs), and efficacy was evaluated using neuropsychological tests. Results: The PBM therapy proved to be safe in regard to the number of recorded AEs (44% of the patients), which were balanced between the PBM and sham groups. AEs were mainly mild, and no serious AEs were reported. The majority of the patients (92.5%) were highly compliant, which confirms the feasibility of the PBM treatment. Compared to the sham patients, the PBM patients showed higher ADAS-Cog comprehension sub-scores and forward verbal spans, and lower TMT-B execution times, which suggests an improvement in cognitive functions. Conclusion: This study demonstrates the tolerability of and patient compliance with a PBM-based treatment for mild-to-moderate AD patients. It highlights encouraging efficacy trends and provides insights for the design of the next phase trial in a larger AD patient sample.
Thesis
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Transcranial photobiomodulation (tPBM) targets the human brain with near-infrared (NIR) light and is shown to affect human cognitive performance and neural electrophysiological activity as well as concentration changes of oxidized cytochrome-c-oxidase ([CCO]) and hemoglobin oxygenation ([HbO]) in human brain. Brain topographical connectivity, which shows the communication between regions of the brain, and its alteration can be assessed to quantify the effects of external stimuli, diseases, and cognitive decline, in resting-state or task-based measurements. Furthermore, understanding the interactions between different physiological representations of neural activity, namely electrophysiological, hemodynamic, and metabolic signals in the human brain, has been an important topic among researchers in recent decades. In my doctoral study, neurophysiological networks were constructed using frequency-domain analyses on oscillations of electroencephalogram (EEG), [CCO], and [HbO] time series that were acquired by a portable EEG and 2-channel broadband near-infrared spectroscopy (2-bbNIRS). Specifically, my dissertation included three aims. The first one was to examine how tPBM altered the topographical connectivity in the electrophysiological oscillations of the resting human brain. As the first step, I defined and found key regions and clusters in the EEG sensor space that were affected the most by tPBM during and after the stimulation using both cluster-based power analysis and graph-based connectivity analysis. The results showed that the right prefrontal 1064-nm tPBM modulates several global and regional electrophysiological networks by shifting the information path towards frontal regions, especially in the beta band. For the second aim, I performed 2-bbNIRS measurements from 26 healthy humans and developed a methodology that enabled quantification of the infra-slow oscillation (ISO) power and connectivity between bilateral frontal regions of the human brain in resting state and in response to frontal tPBM stimulation at different sites and laser wavelengths. As the result, several stable and consistent features were extracted in the resting state of 26 young healthy adults. Moreover, these features were used to reveal some effects of tPBM on prefrontal metabolism and hemodynamics, while illustrating the similarities and differences between different stimulation conditions. Finally, the third aim was to investigate the resting-state prefrontal physiological network and the corresponding modulation in response to left frontal 800-nm tPBM by determining the effective connectivity/coupling between each pair of the electrophysiological, hemodynamic, and metabolic ISO of the human brain. Complementary to the previous studies, my study showed that prefrontal tPBM not only modulates the information path between two locations of the prefrontal cortex, it can also induce unilateral alterations in interactions between neural activity, hemodynamics, and metabolism. Overall, my dissertation shed light on the mechanism of action of prefrontal tPBM.