I agree that the terminology needs to be cleaned up. However, there is another level of confusion that you didn't mention. In the study of cardiac and respiratory oscillations, (www.nature.com/articles/32567) one can find, for example, a pattern of three heart beats per one respiration cycle. This has been referred to as a synchronization, which could be a bit confusing. It has been referred to as a 3:1 phase locking. Maybe we need to create a new term such as "fractional synchronization". I guess that in your studies, fractional synchronization isn't an issue.
Interesting, thanks for posting that. Indeed, terminology isn't only confusing within-domains, it's also confusing across-domains. But the reality is that there isn't much to be done about it except be aware that this issue exists, and try to clarify terms when using them whenever possible.
Thank you for your videos, they are like Christmas presents for me :)). I have one question concerning the illustration at 6:40. An electric signal does decay with some delay through biologic tissue. Could it be that my EEG electrodes are so distant, that I measure antiphase synchrony, although it is actually perfect phase synchrony when the distance is taken into account? Or is the delay too small for that?
Hi Andre. Happy xmas ;) Electrical potentials travel through biological tissue basically instantaneously. True, there are some delays due to the density of the tissue and so on, but these delays are way less than 1 ms at frequencies below 1 kHz. So at the measurement level, it's all instantaneous. Perfect anti-phase synchronization may indicate volume conduction on the other side of the dipole
Hi Mike, Merry Christmas :) Thank you for your fast reply. The only thing I do not understand is why coherence is so often used in research as a measurand for functional connectivity. From my perspective it is inflationary in two ways. Firstly, because of volume conduction and secondly because it consideres antiphase synchrony as functional connectivity, although it has the opposite effect of the transmission of a signal. Would you agree on that?
Volume conduction is an important issue for electrophysiology, but it's not necessarily an unavoidable confound: (1) You can use analysis methods that exclude volume conduction, (2) you can use spatial filters that minimize volume conduction, (3) you can apply tests to distinguish between volume-conducted and real synchronization. I go into this in a lot more depth later in this course and in my book. As for anti-phase synchronization, there is strong theoretical grounding to interpret anti-phase synchronization, which would be one region inhibiting another.
Hello Mike! Thank you so much for your videos! Your interpretations are really helpful and easy to understand. There's one question troubled me recently about this and I would love to hear your opinion! We know that the EEG amplitude varies among people and could show large deviation especially between adults and children. Is it necessary to do normalization (like z-score normalization) before calculating phase-related connectivity, especially when we calculate inter-brain connectivity (hyperscanning)? In other words, does this amplitude deviation between people affect the accuracy of results when calculating phase-related connectivity between two brains? In many works analyzing granger causality based connectivity (like pdc), a normalization procedure is needed for the estimation of causality between the multi-subject MVAR. so i wonder if it's the same in phase-related connectivity.
Amplitude doesn't affect phase, except in the case of very low amplitude, in which case phase is poorly defined or undefined. See czcams.com/video/IYDU9Mj6grQ/video.html&ab_channel=MikeXCohen
Thanks for your videos Mike, they are very helpful and the concepts are uniquely well explained!
I made them just for you, Lucy :)
Your videos are wonderful, I was thinking of analysing fMRI ROI timeseries data using phase synchronisation
Thanks :)
Your videos are amazing. Thank you.
Glad you like them!
This really helped to gain a first insight. Thanks a lot!
Thanks for the video.
ok wow this was exceptionally well explained
Thanks :)
I agree that the terminology needs to be cleaned up. However, there is another level of confusion that you didn't mention. In the study of cardiac and respiratory oscillations, (www.nature.com/articles/32567) one can find, for example, a pattern of three heart beats per one respiration cycle. This has been referred to as a synchronization, which could be a bit confusing. It has been referred to as a 3:1 phase locking. Maybe we need to create a new term such as "fractional synchronization". I guess that in your studies, fractional synchronization isn't an issue.
Interesting, thanks for posting that. Indeed, terminology isn't only confusing within-domains, it's also confusing across-domains. But the reality is that there isn't much to be done about it except be aware that this issue exists, and try to clarify terms when using them whenever possible.
Amazing video! thank you :)
Thank you for your videos, they are like Christmas presents for me :)).
I have one question concerning the illustration at 6:40. An electric signal does decay with some delay through biologic tissue. Could it be that my EEG electrodes are so distant, that I measure antiphase synchrony, although it is actually perfect phase synchrony when the distance is taken into account? Or is the delay too small for that?
Hi Andre. Happy xmas ;)
Electrical potentials travel through biological tissue basically instantaneously. True, there are some delays due to the density of the tissue and so on, but these delays are way less than 1 ms at frequencies below 1 kHz. So at the measurement level, it's all instantaneous. Perfect anti-phase synchronization may indicate volume conduction on the other side of the dipole
Hi Mike, Merry Christmas :)
Thank you for your fast reply. The only thing I do not understand is why coherence is so often used in research as a measurand for functional connectivity. From my perspective it is inflationary in two ways. Firstly, because of volume conduction and secondly because it consideres antiphase synchrony as functional connectivity, although it has the opposite effect of the transmission of a signal. Would you agree on that?
Volume conduction is an important issue for electrophysiology, but it's not necessarily an unavoidable confound: (1) You can use analysis methods that exclude volume conduction, (2) you can use spatial filters that minimize volume conduction, (3) you can apply tests to distinguish between volume-conducted and real synchronization. I go into this in a lot more depth later in this course and in my book.
As for anti-phase synchronization, there is strong theoretical grounding to interpret anti-phase synchronization, which would be one region inhibiting another.
Hello Mike! Thank you so much for your videos! Your interpretations are really helpful and easy to understand. There's one question troubled me recently about this and I would love to hear your opinion! We know that the EEG amplitude varies among people and could show large deviation especially between adults and children. Is it necessary to do normalization (like z-score normalization) before calculating phase-related connectivity, especially when we calculate inter-brain connectivity (hyperscanning)? In other words, does this amplitude deviation between people affect the accuracy of results when calculating phase-related connectivity between two brains? In many works analyzing granger causality based connectivity (like pdc), a normalization procedure is needed for the estimation of causality between the multi-subject MVAR. so i wonder if it's the same in phase-related connectivity.
Amplitude doesn't affect phase, except in the case of very low amplitude, in which case phase is poorly defined or undefined. See czcams.com/video/IYDU9Mj6grQ/video.html&ab_channel=MikeXCohen