[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.

More information about the eeglablist mailing list