Illuminating the Mind: Transcranial Photobiomodulation

A wave of new emerging research with novel insights is illuminating an unexpected path toward cognitive enhancement: transcranial photobiomodulation (tPBM). In their 2024 paper, Nairuz and colleagues dive deep into the application of near-infrared (NIR) light therapy on the brain, exploring its potential to improve attention, memory, and executive function in healthy individuals.

PBM refers to the therapeutic use of red to near-infrared light to influence biological processes at the cellular level, primarily through stimulation of mitochondrial enzymes like cytochrome c oxidase (COX). When applied to the scalp, PBM is believed to enhance ATP production, promote cerebral blood flow, and activate neuroprotective pathways. While neurofeedback and biofeedback involve real-time monitoring and self-regulation of brain or bodily functions, PBM offers a more passive—but potentially powerful—route to modulating brain activity.

In this study, the authors employed transcranial PBM, targeting areas involved in cognitive control using a protocol that spanned several weeks. Their findings offer exciting possibilities not just for cognitive enhancement in healthy individuals, but also for supporting clinical populations facing neurological decline. Still, the results also prompt a deeper reflection: How much of the observed benefit comes from direct neural stimulation, and how much might result from systemic or indirect effects?

Before diving in, a little disclaimer: the results of this study - like many in the field of transcranial photobiomodulation - are very positive, however the mechanisms behind this approach are, to put it bluntly, not understood and are probably not what they seem. It is hugely important, like in ALL fields of science, to critically appraise and discuss these findings. I will try to do just that in the Brendan's Perspective section below.

Methods

The study enrolled 90 healthy adults aged 18–60 and used a randomized, double-blind, placebo-controlled design—a gold standard in clinical research. Participants were divided into three groups: one received PBM with an 810 nm laser device, another received a 1064 nm laser device, and a control group received sham treatment.

Protocol Details:

• Device: Class I lasers delivering light at either 810 nm or 1064 nm.

• Regions Targeted: Right and left dorsolateral prefrontal cortex (DLPFC).

• Sessions: 6 weeks, 3 sessions per week, 20 minutes per session.

• Intensity: Approximately 250 mW/cm² delivered for each targeted region.

A notable strength of the study was its use of brain-derived neurotrophic factor (BDNF) as a biomarker, alongside comprehensive neurocognitive assessments and self-report measures of wellbeing. The authors also employed quantitative EEG (qEEG) in a subset of participants to evaluate potential electrophysiological shifts.

However, it’s important to note that the study did not directly assess intracranial light transmission—an issue we’ll revisit in Brendan’s Perspective.

Results

Participants receiving either 810 nm or 1064 nm PBM demonstrated significant improvements in multiple cognitive domains, including:

• Working memory (as measured by digit span tasks),

• Processing speed, and

• Sustained attention (notably in continuous performance tests).

Subjective wellbeing also improved, particularly in measures of mental clarity and reduced mental fatigue. In a subset of individuals, qEEG showed increases in frontal alpha and beta power, suggesting enhanced neural efficiency.

One of the most compelling outcomes was the increase in serum BDNF levels, particularly in the 1064 nm group. Since BDNF is central to neuroplasticity and cognitive resilience, this biochemical marker adds weight to the behavioral findings.

However, the study lacked long-term follow-up, and did not explore dose-response curves or inter-individual variability—two critical factors for real-world implementation.

Discussion

This research underscores PBM’s growing reputation as a tool for neuromodulation without medication. In clinical contexts, it holds potential for patients who struggle with cognitive impairments, such as those recovering from brain injuries or managing early-stage dementia.

Unlike pharmaceuticals, PBM boasts a favorable safety profile and minimal side effects, making it attractive for integration into holistic care plans. For clients seeking cognitive support, it offers an alternative that is non-invasive and potentially restorative.

From a multidisciplinary perspective, PBM complements existing therapies. While neurofeedback helps clients learn self-regulation, PBM may provide a biological “boost” to enhance receptivity to neuroplastic change. It also opens new doors for clients unable to engage in rigorous cognitive training due to fatigue, pain, or attention difficulties. As such, they can be seen as complimentary techniques.

For professionals in the neurofeedback field, the study raises exciting possibilities. Could we combine PBM with SMR neurofeedback to stabilize attention? Or use it alongside alpha-theta protocols to deepen emotional integration? The electrophysiological shifts observed in the frontal cortex hint at fertile ground for such combined approaches.

Yet the findings must be weighed against mechanistic concerns. As highlighted in the next section, the transcranial delivery of light energy faces major anatomical barriers—a sobering reality that invites critical scrutiny of current assumptions.

Brendan’s Perspective

The elegance of Nairuz et al.’s clinical findings is somewhat clouded by the biophysical limitations highlighted in Tittelmeier et al.’s 2025 article in Brain Stimulation. Their study delivers a crucial reality check: over 99% of near-infrared light is absorbed or scattered before it reaches the brain when applied transcranially.

Using formalin-fixed human skulls and various PBM devices (including 810 and 1070 nm LED helmets), Tittelmeier et al. showed that actual transmittance rarely exceeded 0.71%, and often fell below 0.5%—a level orders of magnitude below what’s needed to trigger mitochondrial activation in cortical neurons .

To generate biological effects in vitro, their team had to use light intensities up to 775 times greater than what reaches the inner skull surface in real-world devices. Even prolonged low-level exposure failed to induce key mitochondrial stress responses or antioxidant activity.

This finding calls for a paradigm shift in how we interpret PBM studies. If the light doesn’t reliably reach cortical tissue, then any observed clinical benefits may stem from indirect mechanisms—perhaps through modulation of skin, scalp vasculature, or systemic neuroimmune pathways.

For EEG neurofeedback practitioners, this raises the need for caution in translating PBM protocols into clinical EEG settings. It also underscores the importance of patient feedback, EEG validation, and individualized protocols. While combining PBM with neurofeedback is an appealing frontier, we must be honest about what we know—and don’t know—about how much light actually reaches the brain.

In practice, a hybrid approach may still hold promise. For example, pairing low-dose PBM as a primer with qEEG-guided SMR training may create a synergy—especially in cases of cognitive fatigue, fibromyalgia, or mild TBI, where systemic effects and cortical tuning often go hand in hand.

Ultimately, clinical neurofeedback is often more adaptive and nuanced than research protocols suggest. While research grapples with strict dose thresholds and skull penetration models, clinicians can individualize treatment by observing real-world responses, guided by EEG and patient outcomes.

Conclusion

Photobiomodulation therapy represents a vibrant and evolving frontier in brain health. The work by Nairuz et al. showcases the real potential for cognitive enhancement using light-based technologies, reinforcing the need for non-invasive and integrative therapies in both wellness and clinical settings.

However, as Tittelmeier et al. remind us, biological plausibility must keep pace with clinical enthusiasm. Whether the benefits of PBM stem from direct neural activation or indirect systemic effects, they still merit our attention—but demand careful interpretation.

The ultimate promise of PBM may lie not in the light alone, but in how we shine it in harmony with other modalities, including neurofeedback, movement therapies, and mind-body approaches. As always in neuroscience, the light we cast must be as rigorous as it is hopeful.

References

• Nairuz, L., Al-Ghamdi, F., Almusned, A., Al-Rasheed, A., & Salehpour, F. (2024). Photobiomodulation Therapy on Brain: Pioneering an Innovative Approach to Revolutionize Cognitive Dynamics. Cells, 13(3), 966. https://doi.org/10.3390/cells13030966

• Tittelmeier, J., Kaub, L., Milz, S., Kugelmann, D., Hof, P. R., Schmitz, C., & Nussbaum-Krammer, C. (2025). Insufficient low-level near infrared light penetration challenges the efficacy of transcranial photobiomodulation. Brain Stimulation, 18, 1220–1223. https://doi.org/10.1016/j.brs.2025.07.001