[Eeglablist] Using a laplacian filter with ICA

[Dickinson, Abigail]

Hi everyone,


I jwondered if anyone could help me with a question I had regarding using a laplacian filter, and at which stage I should implement the  filter. I currently have a processing pipeline which effectively cleans spontaneous data collected from low-functioning children (EGI 128 channel, 500Hz). Due to the nature of our sample I am working with a few constraints, including a high amount of EMG and relatively short recording lengths (1-2 minutes).


The processing pipeline I currently use involves:

-FIR filter (high pass:1Hz, low pass:100Hz)

-remove bad channels

-down-sampling to the 10-20 system 25 channel montage (in order to have an adequate k-factor to run ICA)

-remove bad segments of data

-Run ICA

-Remove artifactual components

-Re-reference to average


I recently saw a paper which advocated the use of a laplacian filter along with ICA to remove EMG (https://www.ncbi.nlm.nih.gov/pubmed/25455426), and also I would like to be able to run cohernece analyses at a channel level, so wanted to re-process this data with a laplacian filter.


However, I cannot apply the laplacian after ICA, as at that point I only have 25 channels. I wondered if anyone could comment on whether it would be appropriate to apply the laplacian filter either on all 128 channels, or after removing bad channels, and then continuing with the rest of the processing pipeline detailed above?


Thanks in advance!


Best wishes,


Abby


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