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Good morning,
<div class="">I am interested in understanding the directed connectivity between the thalamus, where I am recording a Local Field Potential (in 1 channel) and the cortex, where I am recording EEGs (in 16 channels).</div>
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<div class="">My signal is epoched in 4-seconds windows, and I am <b class="">not
</b>interested in understanding the evolution of the directed connectivity <i class="">
<b class="">in time</b></i><span style="font-style: normal;" class=""><b class=""> </b>but rather just which structure is leading which.</span></div>
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<div class="">I have computed <b class="">Partial Directed Connectivity </b>(pdc) with the fieldtrip function
<b class="">ft_connectivityanalysis</b>, feeding into the code the transformed, Fourier spectrum (complex double) of my signal (rpttap x channels x frequencies, where rpttap is repetitions (i.e., number of epochs) x tapers). </div>
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<div class="">My final matrix of pdc is <b class="">17 x 17 x frequencies </b>(where frequencies are my frequencies of interest). The first
<b class="">16 channels</b> represent the <b class="">EEG</b> channels, the <b class="">
17th channel</b> is the <b class="">LFP</b> channel in the <b class="">thalamus</b>. Let’s call this matrix<b class=""> A.</b></div>
<div class="">I have two questions:</div>
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<div class="">1) Did I understand correctly that the element <b class="">A( i, j, f )
</b>for a given frequency f indicates the directed connectivity <b class=""><u class="">from</u> element i
<u class="">to</u> element j? </b>(And not the other way around)</div>
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<div class="">2) In my case, <b class="">A( 1:16 , j , f ) </b>is a column vector containing the
<b class="">same number!</b> </div>
<div class="">It looks like, independently on what EEG channel I am considering (unless I am considering the channel in the thalamus), the contribution of directed connectivity to a certain channel
<b class="">j</b> is always the same. This also stays for the thalamus, so if I take
<b class="">A( 1:16, 17, f )</b>, it seems like all the eeg channels have the same directed connectivity to the thalamus. Is that possible? I think it does not really make sense. Please notice that the numbers are not exactly the same, but differ in the 4th
decimal digit. </div>
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<div class="">Thank you in advance for your help</div>
<div class="">Giovanna</div>
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