**5. Conclusions**

Visual flickering experiments were carried out successfully with fifteen healthy subjects, and their brain responses were recorded using MEG. The two most popular opensource software programs, FieldTrip and Brainstorm, were used to analyze brain source activity. We calculated the event-related coherence of the brain response with the flickering visual signal. Using a recently proposed brain noise estimation method, we computed the relation between the coherent brain network in the visual cortex and corresponding brain noise. The results obtained by the two software programs demonstrated fair agreement. The analyses performed by both MATLAB toolboxes evidenced that more extensive brain activity is accompanied by more substantial brain noise.

**Author Contributions:** Conceptualization, P.C. and S.A.K.; methodology, A.N.P. and A.E.H.; software, P.C. and S.A.K.; validation, A.N.P. and A.E.H.; formal analysis, all authors; investigation, A.N.P. and A.E.H.; resources, A.N.P.; data curation, P.C.; writing—original draft preparation, P.C. and S.A.K.; writing—review and editing, all authors; visualization, P.C. and S.A.K.; supervision, A.N.P. and A.E.H.; project administration, A.N.P. and A.E.H.; funding acquisition, A.N.P. and A.E.H. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by the Spanish Ministry of Economy and Competitiveness SAF2016-80240 in the part of the experimental study and Russian Science Foundation No. 19-12-00050 in the part of the data processing. S.A.K. is supported by the President Program (MD-1921.2020.9) in the part of the source reconstruction.

**Institutional Review Board Statement:** The study was conducted according to the guidelines of the Declaration of Helsinki, and approved by the Ethics Committee of the Technical University of Madrid (protocol No. 19, 3 February 2020).

**Informed Consent Statement:** Informed consent was obtained from all subjects involved in the study.

**Data Availability Statement:** The MEG data have been uploaded at https://zenodo.org/record/44 08648#.X-72UdYo-Cc. Both FieldTrip and Brainstorm codes have been uploaded as a single release at https://zenodo.org/record/4408756#.X-77itYo-Cc.

**Acknowledgments:** The authors graciously acknowledge the subjects for their contribution to this research.

**Conflicts of Interest:** The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.
