[Eeglablist] How to take care of signal discontinuities following artifact rejection of continuous data

[Makoto Miyakoshi]

Dear Nike,

> When we run ICA on the continuous data after artifact rejection, aren't
these abrupt transitions going to affect my ICA results ?

No, because ICA shuffles all the datapoints for every iteration. Are you
surprised? It means that ICA does not know extension of time, it only cares
inter-channel relation for each time points.

> How can I extract epochs such that none of my epochs contain the the
abrupt transitions ?

That's impossible. There are techniques such as windowing, blending, etc to
reduce the abruptness, but epoching does not use them (and do not need to
use them).

> I am guessing that I have to use the BOUNDARY marks, but am not sure how.

If you have boundary events, eeglab filter process will not go across it
but uses windowing function to fade out/fade in before and after the
boundary. Epoching will reject any epoch that contain boundary, etc.

Makoto

On Sun, Sep 6, 2015 at 11:48 PM, Nike gnanateja <nikegnanateja at gmail.com>
wrote:

>
> Dear List,
>
> I have recently shifted from artifact rejection of epoched data to
> continuous data. In the process I have noticed that artifact rejection of
> continuous data leads to abrupt transitions/discontinuities in the signal.
> wont these discontinuities affect the later stages of processing. I have a
> few questions on this issue
>
> When we run ICA on the continuous data after artifact rejection, aren't
> these abrupt transitions going to affect my ICA results ?
>
> How can I extract epochs such that none of my epochs contain the the
> abrupt transitions ? I am guessing that I have to use the BOUNDARY marks,
> but am not sure how.
>
>
> regards,
>
> Nike
> --
> G Nike Gnanateja, MSc (Audiology) <http://goog_636235333>
> Junior Research Fellow,
> Department of Audiology,
> All India Institute of Speech
> and Hearing Mysore-06
>
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-- 
Makoto Miyakoshi
Swartz Center for Computational Neuroscience
Institute for Neural Computation, University of California San Diego
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