*4.3. Limitations*

The first limitation of this exploratory study is obviously the small sample size. While for some psychophysical designs this numerosity may be reasonable, to provide good statistical power, and also to address possible individual differences, the number of participants should be increased.

Another limitation is the small number of EEG electrodes. With eight electrodes, we did not even attempt to compute a spatial map of cortical activity. This issue should be addressed with more sophisticated EEG recordings and analyses. Our goal here was simply to provide initial evidence of cortical entrainment.

We should also note a limitation of the experimental design. For practical reasons, we administered the cortical recording session before the perceptual session. This could have introduced a carry-over effect, i.e., observers' higher sensitivity in the perceptual session as a result of learning. This could be one reason for the steeper rise of perceptual responses with video speed modulation amplitude, as compared to cortical responses. Note, however, that the direction of such carry-over effect, if any (the cortical session being administered before the perceptual session, and not vice-versa), would reinforce the evidence for a dissociation between cortical and perceptual responses: the perceptual responses in the trials with the lowest speed modulation strength were statistically indistinguishable from the responses in the trials without speed modulation, despite the possible beneficial effect of previous exposure to the stimuli.

**Funding:** This research was partly funded by *Fondazione Cariplo*, gran<sup>t</sup> #2018-0858. **Acknowledgments:** The author thanks Luca Mesin, Tatiana Baroni, and Regina Gregori-Grgiˇc for their help with EEG instrumentation, recordings, and analyses.

**Conflicts of Interest:** The author declares no conflict of interest.
