Demonstration of Alpha-Band Entrainment via Low-Field Magnetic Stimulation: A Simulation-Driven Proof of Concept

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This manuscript presents an interesting attempt to integrate electromagnetic modeling with electrophysiological measurements to explore whether 10 Hz low-field magnetic stimulation can modulate occipital alpha-band activity. However, several issues require clarification to ensure methodological rigor and interpretative validity.

1. Regarding the study design, please clarify why no sham stimulation condition was included. A pre–post comparison alone does not sufficiently exclude nonspecific effects such as resting-state variability, changes in vigilance, or time-dependent fluctuations. Please provide a clear rationale for attributing the observed alpha power increase specifically to the stimulation.
2. Please specify the sample size and provide details of the statistical analysis. Was an a priori power analysis conducted? The reported “increase exceeding 140%” should be clarified: does this represent a mean effect across subjects, a median value, or a subset of participants? Please report statistical significance levels, effect sizes, and whether corrections for multiple comparisons were applied.

3, Alpha-band activity is highly sensitive to eye state and vigilance level. Please describe how eye condition (eyes open vs. closed), visual input, and arousal were controlled during EEG acquisition. Were EOG or other physiological measures used for artifact rejection and vigilance monitoring?

4. Although Maxwell–Faraday induction is referenced, the magnitude of the induced electric field (in V/m) was not quantified. Please provide estimates of the induced electric field strength within cortical tissue and discuss how these values compare with known physiological thresholds reported in the weak-field neuromodulation literature.
5. The use of a simplified spherical head model omits multilayer conductivity differences (skull, CSF, gray and white matter) and cortical geometry. Please discuss how this simplification may affect the accuracy of field distribution predictions and whether any estimation of modeling error was performed.
6. The comparison between the solenoid coil and the figure-of-eight coil would benefit from quantitative metrics. Please provide numerical comparisons of magnetic flux density, dB/dt, spatial focality (e.g., full width at half maximum), or gradient magnitude under identical stimulation conditions.
7. The use of a sawtooth waveform inherently introduces harmonic components. Please clarify how you determined that the observed alpha enhancement was driven by the 10 Hz fundamental component rather than higher harmonics. Have you considered comparing the sawtooth waveform with a pure sinusoidal 10 Hz stimulation?
8. Please clarify whether the reported alpha increase reflects absolute power enhancement or relative power redistribution. To support the claim that this effect is not a global amplification of EEG power, please provide quantitative analysis of broadband power changes.
9. Did the increase in alpha power coincide with changes in phase synchronization, coherence, or functional connectivity? Power redistribution alone may not fully characterize modulation of oscillatory network dynamics.
10. The manuscript suggests that electric fields below classical depolarization thresholds may influence neural activity if temporally aligned with intrinsic oscillations. Please elaborate on the mechanistic basis for this claim and clarify whether the induced field strengths in your study fall within theoretically relevant ranges.
11. The interpretation of the findings as “proof of concept” should be more precisely defined. Please clarify whether the present data constitute direct evidence of frequency-specific neuromodulation or preliminary observations that cannot yet exclude alternative explanations.

Addressing these points with quantitative detail and methodological clarification would substantially strengthen the scientific rigor and interpretative confidence of the manuscript.

Author Response

Please see the attachment. There you will find the point-by-point responses in word format. Thank you.

Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

Comments and Suggestions for Authors

The manuscript presents a technically sound and well-documented proof of concept exploring the association between low-field magnetic stimulation (LFMS) at 10 Hz and occipital alpha-band EEG modulation. The integration of electromagnetic simulations, coil design optimization, and EEG spectral analysis is appropriate for an engineering-oriented journal and represents a valuable exploratory contribution.

However, several points require clarification and reframing to ensure that the conclusions accurately reflect the preliminary and exploratory nature of the study.

Clarification of Scope and Study Aim
The EEG analysis is based on a single participant. While this is acceptable for a feasibility or demonstration study, the manuscript should explicitly state that the EEG results are illustrative and exploratory, and that no inference regarding efficacy, reproducibility, or generalizability can be drawn.

Lack of Control or Sham Condition
The absence of a sham or control condition should be more clearly acknowledged as a major limitation. Given the known sensitivity of occipital alpha activity to resting-state conditions (e.g., eye closure, relaxation, time-on-task), the observed alpha-band changes cannot be uniquely attributed to LFMS.

Interpretation of Alpha-Band Changes
Some statements in the Discussion and Conclusions imply functional or physiological effects (e.g., increased relaxation or effectiveness of the device). These interpretations should be softened. It is recommended to describe the findings primarily as a redistribution of spectral power toward the alpha band, without linking them to behavioral or emotional outcomes.

Induced Electric Field Considerations
Although Faraday induction and weak-field neuromodulation mechanisms are discussed, the induced electric field within the head model is not quantified. Even a simplified or order-of-magnitude estimate of the induced electric field would strengthen the mechanistic interpretation and the engineering rationale of the study.

Stimulation Waveform and Frequency Specificity
The use of a sawtooth waveform introduces multiple harmonic components across frequency bands. While this is acknowledged, the manuscript should more clearly state that strict frequency specificity cannot be conclusively demonstrated under these stimulation conditions.

Modeling Simplifications
The spherical head model with homogeneous magnetic susceptibility is acceptable for a proof-of-concept study, but it should be more explicitly described as a simplified approximation that does not account for cortical geometry or tissue heterogeneity.

Addressing these points mainly requires clarification, reframing, and cautious interpretation, rather than additional experimental data.

Author Response

Please see the attachment. There you will find the point-by-point responses in word format. Thank you.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The authors of the manuscript have provided appropriate responses to the reviewer’s comments and have revised and improved the manuscript accordingly. Therefore, I recommend this paper for publication.

Author Response

Thank you very much for the positive feedback!

Reviewer 2 Report

Comments and Suggestions for Authors

The authors have adequately addressed the main concerns raised in the previous review round. The manuscript has improved in clarity and is now more appropriately framed as an exploratory, proof-of-concept study.

Some minor refinements could further enhance consistency and readability.
The terminology describing the stimulation mechanism should be fully harmonized across the manuscript, particularly regarding the distinction between “frequency-specific” and frequency-aligned effects.

A few expressions remain slightly stronger than warranted by the study design; adopting more neutral wording (e.g., “preliminary evidence” or “observed association”) would further align the interpretation with the exploratory nature of the work.

The section describing the electric field estimation is a useful addition and could benefit from a brief clarification that the reported values are approximate and model-dependent.

Finally, small editorial adjustments, including removal of redundancy in the abstract and improved consistency of terminology, would further strengthen the manuscript.

Overall, the manuscript is much improved and could be suitable for publication after minor revision.

Author Response

Please see the attachment. Thank you!

Author Response File: Author Response.pdf