Connectionists: Statistical Analysis of coherence and PLV (phase-locking value)

[vic roc]

 Dear cognitive neuroscientists

Hope you are perfectly well.

I had two questions regarding the statistical analysis of PLV and coherence:

1. Can I directly interpret the “grand average PLV values” or “grand
average coherence values” as indicators of connectivity?

2. Can I treat these PLV or coherence values as some sort of “raw data” to
be analyzed and compared statistically across subjects?

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More explanation about 1 (1. Can I directly interpret the “grand average
PLV values” or “grand average coherence values” as indicators of
connectivity?) :

These two measures seem to be some directionless correlation coefficients
(like r-squared), right? If yes, so I guess I can directly interpret them?
There is no P value attached to them. Still, I can say for example those
above 0.7 are strong and those above 0.9 are excellent correlations. So can
I look at the “Grand Average” PLVs (average of average PLVs of all subjects
in a particular condition/group) and find those grand-average PLVs that are
above, say, 70% across all the subjects, and list their responsible pairs
of electrodes (channels) as strongly correlated and thus as “strongly
functionally connected”? I can do the same for those between 50% and 70%,
calling their electrodes (channels) to be moderately connected. Is this
method possible? Please let me know about any other similar analyses I can
do.

———————

More explanation about 2 (2. Can I treat these PLV or coherence values as
some sort of “raw data” to be analyzed and compared statistically across
subjects?):

Can I compare these PLV values or coherence values across all the different
conditions (different interventions), using analyses such as ANOVA and post
hoc tests? For example, let’s say we have 3 conditions, each with 30
subjects. And each subject has many, many PLV values between all possible
pairs of electrodes. But the number of PLV values is the same for all
subjects since all of them have been scanned with the same EEG device.

Can I compare each PLV value of all my 90 subjects (within 3 groups) with
each other, in terms of their 3 conditions (interventions), using ANOVA and
Tukey or some other appropriate statistical test?

I mean is it correct to treat these “correlation coefficients” named PLV or
coherence as raw data, and statistically analyze them?

Thanks a lot in advance.
Best,
Vic
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