Delay in ms between twwo electrodes

[Davide Momi]

Hi Mike, 

I'm working with a TMS-EEG dataset where the TMS pulse was delivered on the left M1. I would like to estimate the average delay in ms between two electrodes (C3 and C4) after the stimulation pulse. 

So, firstly I calculate the power and phase connectivity between C3 and C4 (cormat.mat attached) for all the frequencies spanning from 3 to 80. Then, I selected where the maximum correlation and see at what frequency this is going to happen. Lastly, I used that frequency to create a Morlet Wavelet and than filter the signal and estimate the time lag in ms via phase synchronization. 

However for all my subjects I got really different results which is highly unlikely. 

Glossary of the uploaded files:

- C3_C4_connectivity.mat = it is the script that I used to estimate the power and phase connectivity

- corrmat_V1.mat : it's the correlation matrix for all 24 subjects

- Delay C3_C4.mat = it's the script to estimate the time delay

Thanks in advance for all your help

Davide 

[Mike X Cohen]

Hi Davide. Do you need to do this analysis in the frequency domain? I would think that the direct TMS-evoked connections might be better off quantified in the time domain, where you don't have to worry about temporal smearing or potential contamination of the TMS artifact. Maybe it would be sensible to find the first post-stimulus peak and then grab the peak time at different electrodes?

Mike

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Mike X Cohen, PhD
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