[FieldTrip] coherence/connectivity measures after applying ICA

[Tessa van Leeuwen]

Dear Fieldtrip experts,

I have noticed enhanced coherence (sensor level) in my data after applying ICA during preprocessing, removing only 1 EOG component. Of course the (mainly quantitatively) enhanced coherence could be due to the removal of (artifact induced) noise from the data. But this increase also occured when applying ICA to previously cleaned data, implying changes induced by ICA somehow affect coherence.

One of the aims of our project is to compute coherence/connectivity measures at the source level. Since connectivity measures are often difficult to interpret as they are, I would like to ask whether anyone has experience with connectivity analyses after preprocessing that involved ICA. Are people aware of possible influences of ICA on connectivity measures and is there a way to deal with this? Or would it be advisable NOT to use ICA when later looking at coherence/connectivity at the source level? 

We initially aim to compare across conditions (data that have been preprocessed together and from which the same ICA component has been removed). But we also have different experimental groups for which we would like to qualitatively compare active networks during our task.

Thank you in advance for any input, it is highly appreciated.

Best wishes,
Tessa


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Tessa van Leeuwen, PhD
postdoctoral researcher

Department of Neurophysiology
Max Planck Institute for Brain Research