[Eeglablist] Re-referencing drastically changes my power spectrum

[Andreas Widmann]

Hi Ulrich,

Would you mind sharing an affected sample file and your code used for analysis?

Best,
Andreas

> Am 16.08.2024 um 17:09 schrieb Ulrich Pomper via eeglablist <eeglablist at sccn.ucsd.edu>:
> 
> Dear EEGlab list,
> 
> I have a question regarding to order of two common preprocessing steps: filtering and re-referencing to common average.
> 
> In my current EEG study, I initially filter the raw, continuous data into low (2-12 Hz) and high frequency components (13 - 80 Hz), and afterwards re-reference the data to common average. However, this re-referencing step really messes up the spectrum of the data in a way that makes me suspect an error (please see panels 7 and 8 in this figure [1]).
> 
> When I re-reference first and filter second, on the other hand, the spectrum stays intact and the data seem OK (see panels 5 and 6).
> 
> I was hoping that someone might be able to explain to me what is going on here, and potentially confirm that re-referencing first and filtering second is actually the correct way to go.
> 
> I'd highly appreciate any input!
> 
> Many thanks,
> 
> Ulrich
> 
> -- 
> Dr. Ulrich Pomper
> 
> Senior Scientist
> Department of Cognition, Emotion, and Methods in Psychology
> University of Vienna
> Liebiggasse 5
> 1010 Vienna
> Austria
> 
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> ulrich.pomper at univie.ac.at
> +43-1-4277-47149 [3]
> 
> 
> 
> Links:
> ------
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