[Eeglablist] Using a laplacian filter with ICA

Makoto Miyakoshi mmiyakoshi at ucsd.edu
Thu Jan 12 22:55:39 PST 2017

Dear Abby,

That's a new method for me and I don't know how it works. From the
abstract, it seems you apply ICA, reject muscle components, then Laplacian?
If so, the question is when you want to perform the average reference.
Probably you want to average reference after Laplacian so that the computed
average reference is EMG free (not exactly free, but very much removed?)

By the way, ICA cannot decompose EMG becaues EMG source spreads along with
muscle fibers, so my former colleague told me. Empirically, I also
experienced that muscle is harder to decomposed compared with other typical
artifacts such as eyes, which makes sense.

>From Lufthansa455 to Frankfurt,


On Tue, Jan 10, 2017 at 10:28 AM, Dickinson, Abigail <
ADickinson at mednet.ucla.edu> wrote:

> 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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Makoto Miyakoshi
Swartz Center for Computational Neuroscience
Institute for Neural Computation, University of California San Diego
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