Hi,

I am working on resting state EEG data, and I have two groups controls and patients, for which I would like to calculate the coherence between scouts of interest for each subject (1xN), as we would like to know which group has an increased or decreased connectivity for a particular frequency band. So I tested using both the magnitude square coherence and imaginary coherence method.

I had calculated the source per subject and per trial using the sLORETA method for unconstrained sources and the head model was calculated using the BEM (volume) option.

I calculated the coherence (A x B) by adding the trials for each subject into process 2 and selecting the source option, followed by selecting 1 scout each of interest from A and B (the volume atlas was same for both). The scout function was: mean, apply the scout option was: before. The window length for PSD estimation was 0.5 (I have 1 second trials), overlap was 50% and highest frequency of interest was 30 Hz. I had selected the output as average cross spectra.

I am seeing for example for a subject, with the magnitude squared coherence method I am getting a coherence peak at 4.8 Hz, while if I use the imaginary coherence method then I am getting a peak at 8.7 and 13.6 Hz.

Am I doing something wrong? Is there any preference as to which method should be used? since this would effect our results and hypothesis in a big way.

Any help regarding this is greatly appreciated.

Thank you so much.

Best,

Ami