[FieldTrip] coherence/connectivity measures after applying ICA

[Rodolphe Nenert]

Dear Tessa,
would it be possible to give some precision about your analyzes.

1) After your first "cleaning", do you test coherence on particular
components or your entire data minus the "EOG" component?

2) When you say that you redo ICA on cleaned data (of course, an ICA
analysis made on a result of a previous ICA analysis with components
removed is a bad idea), do you remove another component or do you  test
your coherence on particular components?

Rodolphe

On Tue, Mar 27, 2012 at 11:27 AM, Tessa van Leeuwen <
tessa.vanleeuwen at fcdonders.ru.nl> wrote:

> 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
>
>
> ---
>
> Tessa van Leeuwen, PhD
> postdoctoral researcher
>
> Department of Neurophysiology
> Max Planck Institute for Brain Research
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