Reference for PLV score threshold (INTER brain connection)

Hello Mike,

I would like to ask you since I am doing the analysis of Phase-based connectivity analysis (Phase Locking Value). I have looked at your video (min 15:22) in which you said that PLV score of EEG is maximum up to 0.4 / 0.5, even though PLV is between 0.1 - 1 actually. If it is above that, it could be affected by volume conduction. Due to that, would you like to let me know is there any specific paper that I can refer to for that ?

Also, If I have not misunderstood your explanation, you explained that video with the assumption of doing INTRA-brain channel connection. For me, I am doing INTER-brain channel connection (eg. FP1 of Subject 1 and FP1 of Subject 2). Due to the nature of the experiment, is it possible for me to take the PLV score above 0.5 since the INTER-brain connection is “not” affected so much by volume conduction ?

I would like to thank you in advanced and look forward to your reply and advice


Hi Ihshan. That “threshold” of .4/.5 is based on my experiences analyzing and simulating data, and reviewing lots of other papers and findings. It’s more an intuition than a concrete threshold. The thing is that neural synchronization is beneficial up to a point; the brain tries to avoid really strong synchronization, as that generally leads to pathological conditions like epilepsy.

Obviously, for inter-person synchronization, there is no volume conduction. The main potential alternative explanation that I can see (without knowing anything about your experiment) is that the two individuals are independently synchronizing to an external stimulus, as opposed to being synchronized to each other.

As an aside, I’ve often wondered whether something like direct brain-to-brain electrical communication (e.g., ephaptic coupling) is possible between two people swimming in the dead sea, given the high salt concentration, which is a highly electrically conductive medium.

Hi Mike,

Thank you so much for your reply. That is what we are trying to find out how external factor could help or mediate brain synchronization between two people or more.

Your idea is interesting to explore :). If we go to the dead sea we can float automatically due to the high concentration of salt.