[FieldTrip] plv and sourceanalysis

Maren Grigutsch grigu at cbs.mpg.de
Thu Apr 7 15:19:17 CEST 2011

jan-mathijs schoffelen wrote:
> Dear Stan,
> Here is my take on it:
>> Speaking of plv, two weeks ago I sent out a question regarding plv, 
>> but I don't recall getting any responses. My questions were:
>> 1) By ignoring the phasor magnitudes when summing over trials, isn't 
>> plv noisier than standard coherence that includes magnitudes?
> Yes

Yes, if your signals are coherent.  But I would not say that plv and 
coherence are just two different measures for the same thing. There 
exist dynamic regimes where only the phases of oscillators are coupled 
and the amplitudes are not. This type of coupling can be detected by 
measuring plv but not by computing coherence.

>> 2) By including the real part isn't plv often dominated by volume 
>> conduction that can be avoided by just looking at the imaginary part 
>> of coherence (sadly the imaginary part may be hard to interpret and 
>> it ignores the non-volume conducting contributions to the real part).
> I agree. What's the question here?
> Best wishes,
> Jan-Mathijs
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Max Planck Institute for Human Cognitive and Brain Sciences
Dipl.-Phys. Maren Grigutsch     mailto:grigu at cbs.mpg.de
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