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Dear SPMers,

I have a question about removing eyeblink artefacts using the topography-based artefact correction described in 'Advanced topics in M/EEG artefact removal chapter (40) of the SPM12 manual.
I am cleaning EEG data.

On the majority of my data files, the topography-based correction method has worked well. However, on some files, the method fails to detect components on the topography. I successfully model the eyeblink using the 'detect artefacts' batch, and successfully epoch around the eyeblinks. The issue happens when I run 'define spatial confounds'. No blink-related components are detected.

In some files, the topography is blank but for a few small areas. This suggests a strong artefact is creating so much noise in the data that the component is not being detected. However, I tried running a lenient (150uv) artefact rejection on the file, this causes all trials to be rejected. Running an 80uv artefact rejection on the normal (non eyeblink) data file does not cause all trials to be rejected.
Also, marking the artefacts and rejecting using the 'threshold Z-scored difference data' function (also described in chapter 40 of the manual) does not change the fact that the components are not detected.

Would anyone have any advice on how to resolve this issue? I would be very grateful for any ideas.

Many thanks!
Emily Hird