[Eeglablist] Too much drift with just 0.1hz high-pass filtering?

Kevin Tan kevintan at cmu.edu
Tue Aug 4 22:20:15 PDT 2015

Hi all,

There are numerous papers that conclude that >0.1hz high-pass filtering
distorts ERPs. However, I notice a lot of remaining drift after 0.1hz
hi-pass, especially compared to 1hz hi-pass. I'm using a BioSemi Active2

0.1hz hi-pass:

1hz hi-pass:

Is the drift in 0.1hz data ok? I get 'better looking' ERP waveforms & more
robust differences between conditions in 0.1hz data – I'm worried this is
mostly due to drift.

The 1hz data has ERP 'distortions': negative slope from start of epoch
until P1 & negative deflection of later components. Thus, I'm not
comfortable with either of the filters.

The screenshots show data run only through 1) PREP pipeline 2) high-pass
filtering 3) epoching. The final cleaned data shows the same drift.

My full preproc stream:

ICA dataset:
> - Load PREP'd data
> - 1hz hi-pass
> - Epoch
> - Epoch rejection
> - Extended ICA (binica)
> - Determine bad ICs

Final dataset:
> - Load (unfiltered) PREP'd data
> - 0.1hz hi-pass (tried 1hz for comparison too)
> - Epoch
> - Generate ICs from matrices of ICA dataset
> - Remove bad ICs determined from ICA dataset
> - Epoch rejection
> - Make ERPs

Any input would be much appreciated!

Many thanks,
Kevin Alastair M. Tan
Lab Manager/Research Assistant
Department of Psychology & Center for the Neural Basis of Cognition
Carnegie Mellon University

Baker Hall 434
 | kevintan at cmu.edu | tarrlab.org/kevintan
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