Dear list,
I have a problem with strong activation in the cfs and white matter in the analysis of an event-related fMRI experiment I did. No matter how I preprocess and analyze my data, I can't get rid of this csf and white matter activity in about a third of my subjects. In addition to the standard preprocessing steps, I added csf and white matter regressors, added the motion parameters, tried it with the motion outliers included and finally did an ICA, removing components that show strong csf and/or white matter activity. With all these steps the unwanted activity gets a bit smaller but the effects are surprisingly little. Especically with the csf and white matter regressors I see almost no effect. This surprised me and I would like to know if others have made similare experiences.
Since I'm using pain stimuli, it is likely the csf and white matter activity is cause by stimulus related motion. Nevertheless, I'm confused how strong and resistand to any correction steps this activation is. Has anyone had similar problems and is there anything I can do in addtion about this?
Thx,
Susanne
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