[Eeglablist] Referencing Details

Official Mike mikesterich at gmail.com
Mon Nov 8 06:55:54 PST 2021


Dear EEGlab list,

I have 65 channel EEG which was online referenced to Cz (channel 65).
Couple questions:
1. When setting the reference in the 'Edit channel info' window, I set the
Reference field to Cz, but should the 'Channel Indices' field be set to
1:64 or 1:65 (so including the reference channel)?

2. I want to reconstruct the Cz signal by re-referencing it (offline) in
the 'Re-reference window'. I know a common way to reconstruct a channel
signal is by re-referencing all channels to the Average. But are there also
other ways? I read somewhere that re-referencing the data to Cz itself can
reconstruct it, but this doesn't make sense.

3. What is the difference between setting a reference in the 'Channel info'
window versus setting a reference in the 'Re-reference' window? E.g. if the
reference is unknown when loading the EEG data, and I want to set Cz as the
reference first.

4. I only select 16 channels for further analysis, thus removing the
others. Is it better to select these channels after re-referencing to the
Average or to do the re-reference after channel selection so that the
average is only of those 16? I feel like it's unfair to average reference
to channels that you will not use later on, especially if it's 48 out of 64.

5. Can I re-reference all 64 channels to a channel that is removed after I
select a subset of 16 to focus my analysis on? Thus those 16 do not contain
the reference.

6. If Cz is already my reference, is it perhaps better to avoid
re-referencing to the Average so that other channels do not get
contaminated with noise? The downside to this of course is that I won't be
able to analyze Cz activity, but that seems worth it compared to lowering
the quality of other channels.

Thank you for any help and all the best.
~Mike


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