[Eeglablist] about using the tip of nose as reference channel

[Hui-bin Jia]

Hi, all
 
 
 
      In my ERP experiment, all EEG electrodes were referenced online to FCz. But during the preprocessing of EEG data, they should be re-referenced to the channel on the tip of nose. 
 
 
 
      Because the tip of nose is in the vicinity of eyes, it has a lot of VEOG signals. If VEOG and HEOG signals are partly removed by ICA, using this channel as reference  
 
may seriously affect the result. So in order to gain reasonable ERP waveforms, the VEOG & HEOG signals should be perfectly removed.  
 
 
 
 
 
    Could someone give me some tips and cautions during the preprocessing?  How to remove the VEOG & HEOG signals perfectly 
 
without losing the genuine brain signals?
 
 
 
     Besides I have the following questions:
 
1.       If I want to use ICA to remove artifacts, is it a good idea that the VEOG channel is excluded before run ICA ?  The HEOG channel is placed on the tip of nose, and the VEOG channel is placed below the eyelid of the left eye.
 
2.        Before run ica, the continuous EEG data was segmented into stimulus-locked ERP epochs of 3000ms(-1000ms to 2000ms) and filtered at 1~30Hz. Is it necessary that the epochs is baseline corrected?
 
3.       When should I re-reference the channels to the channel on the tip of nose(i.e., the HEOG channel)? Before run ICA or after the independent components related to VEOG &HEOG is removed?
 
4.       How to efficiently identify the ICs that related to VEOG & HEOG. Is it a good idea to calculate the Pearson correlation coefficients between ICs and VEOG channel ? 
 
 
 
Any reply from you will be highly appreciated!
 
 
 
Hui-bin Jia
 
Faculty of Psychology, Southwest University, China
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