[Eeglablist] Makoto's preprocessing pipeline: ICA matrices transfer

Scott Makeig smakeig at gmail.com
Thu Oct 7 10:09:39 PDT 2021


Ya -

Why do you bandlimit 1-35 Hz before applying ICA decomposition? The upper
limit is best left open, as ICA decomposition can use spatially
differentiating information contained in higher frequency portions of the
source signals. The (~1 Hz) lower limit is justified by the understanding
that very-low-frequency contributions may be dominated by non-brain
artifact processes that would compete with brain sources for
places/separate dimensions in the decomposition. If the same were to occur
at high frequencies (e.g., hypothetically, say, *spatially* complex and
varying broadband 100-150 Hz noise), then using a high-pass cutoff (e.g., <
100 Hz) would be justified by the same reasoning.

Likely your finding that ICLabel returns more EMG sources when applied to
the 0.1-Hz high-passed data (without low pass filtering) arises because
ICLabel looks for the spectral signature of EMG (conceptually, a noise
plateau from 20 Hz  to max Hz) as well as for scalp map characteristics,
and doesn't see the spectral signature it is looking for in the 35-Hz
low-passed data...

Scott

On Thu, Oct 7, 2021 at 12:21 PM Ya Zheng via eeglablist <
eeglablist at sccn.ucsd.edu> wrote:

> Hi Makoto,
> I calculated ICA weight matrix and sphereing matrix with 1-35 Hz
> band-passed data, then appled it to 0.1-Hz high-passed data. Then, I
> applied the ICLabel to identify the artifact-related ICs. My question is
> which dataset should be applied to? The 1-35 band-passed data or the 0.1-Hz
> high-passed data? I found that the ICLabel resulted in some different
> results, e.g, more muscle ICs found for the 0.1-Hz high-pass data. Thanks!
> Best,
> Ya
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-- 
Scott Makeig, Research Scientist and Director, Swartz Center for
Computational Neuroscience, Institute for Neural Computation, University of
California San Diego, La Jolla CA 92093-0559, http://sccn.ucsd.edu/~scott


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