strange sensor signals in the baseline

[Michael Wibral]

Dear Fieldtrippers,

I have some data from a 275ch CTF system, that were (in each single subject) preprocessed in Fieldtrip with baseline correction and detrending. If I now look at the grandaverage ERP some sensors have a nonzero signal that is entirely on one side (either completely above or completely below) of the baseline, while most sensors oscillate around zero as I would expect. Is this an effect of detrending, i.e. is detrending performed AFTER baseline correction AND on the whole datapiece, instead of just the specified baseline interval?

Any suggestions welcome.

Michael


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