On 5 May 2014, at 16:11, Andreas Lidström <[log in to unmask]> wrote:

Allright, so during the FSL course I asked if you should do individual ICA analyses to clean my data prior to feeding it into a concat gICA, and I got the answer that I could just run the gICA directly as any artifact would get picked up in components anyway. Also, the information on the website states that the data used in the ICA practical session had been artifact-removed using FIX, so further insight would be appreciated.

Not sure who said exactly what - but yes it can help somewhat that the dualreg is a) a multiple regression rather than single and b) strong group-level artefacts included in that can help ameliorate artefacts.

However, in general it would be better to remove artefacts within-run before doing the group-ICA and dualreg - e.g. with FIX or by identifying within-run-ICA components by hand.

Two questions:

1. Is it worth running ICA on unclean data, and if so, is it better to let MELODIC estimate the number of components if no cleanup is done?

in general yes and yes.

2. What are the benefits of doing cleanup on your data first?

all things being equal there's a better chance of overall cleaner results this way.

Cheers.

This question arose since I want to know how MELODIC handles a subject with unique artifacts in a gICA for instance.

//Andreas

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Stephen M. Smith, Professor of Biomedical Engineering
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