Brief and localized pulsed transcranial photobiomodulation cumulatively increases EEG power across the brain in healthy young adults
Bibliographic record
Abstract
ABSTRACT Objectives Transcranial photobiomodulation (tPBM) modulates cortical activity, but how specific stimulation parameters shape the electrophysiological response remains unclear. We tested whether pulsed forehead tPBM produces frequency band-specific EEG changes, whether pulsation frequency entrains endogenous oscillations, and whether wavelength, pulsation frequency, irradiance, sex, and skin tone significantly modulate the response. Materials and Methods Forty-six healthy young adults (24M/22F, 20-32 years) each completed four 12-minute EEG recordings (256-channel; PRE-DURING-POST, 4 min each) with pulsed NIR light delivered to the right forehead. The parameter space included two wavelengths (808 nm, 1064 nm), two pulsation frequencies (10 Hz, 40 Hz), and three irradiances (100, 150, 200 mW/cm 2 ). Forehead skin tone (ITA) and sex were included as biological moderators. EEG band power (delta through gamma) was expressed as percent change from a pre-stimulus baseline. Spatiotemporal cluster-based permutation tests (10,000 permutations, FWER alpha=0.05) identified significant electrode clusters. Linear mixed-effects models with backward elimination and FDR correction (q=0.05) quantified parameter and biological contributions. Results tPBM produced bilateral, bidirectional EEG changes: frontal gamma enhancement and posterior theta, alpha, and beta suppression, emerging gradually during stimulation and persisting post-stimulation. Wavelength qualitatively shaped the response: 808 nm drove broadband posterior suppression while 1064 nm selectively enhanced frontal gamma. Contrary to entrainment predictions, 10 Hz pulsation produced significantly larger gamma increases and theta reductions than 40 Hz. Sex was the most consistent biological modulator: females showed greater alpha suppression during stimulation and males showed greater posterior beta and gamma suppression. Irradiance and skin tone were not significant. Conclusions Pulsed forehead tPBM produces robust, parameter-dependent EEG changes that are not consistent with neural entrainment. Wavelength determines the character of the cortical response, pulsation frequency modulates its magnitude, potentially through photobiological rather than oscillatory mechanisms, and sex is a significant biological moderator. These findings contribute toward a human-specific foundation for informing optical tPBM parameter selection.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".