[Eeglablist] Handling Abrupt Changes After ASR Preprocessing

[Richards, John]

You can taper the ends of the segments to avoid abrupt changes; similar to tapering the ends of a time series before doing FFT.   Google "taper ends of time series" or "taper concatenated time series".  This will avoid throwing abrupt changes in the time series which will affect frequency analyses.  Ultimately concatenated data will disrupt any analysis where the phase of a regular frequency pattern is interrupted by the concatenation.  John

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John E. Richards
Carolina Distinguished Professor
Department of Psychology
University of South Carolina
Columbia, SC  29208
Dept Phone: 803 777 2079
Fax: 803 777 9558
Email: richards-john at sc.edu
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-----Original Message-----
From: eeglablist <eeglablist-bounces at sccn.ucsd.edu> On Behalf Of Hanna Szakács via eeglablist
Sent: Monday, October 7, 2024 2:53 PM
To: 和田真孝 <masa.wada0622 at gmail.com>
Cc: eeglablist at sccn.ucsd.edu
Subject: Re: [Eeglablist] Handling Abrupt Changes After ASR Preprocessing

Hi, this is something that interests me as well and I haven't found a clear answer online or on the EEGLAB forums so far. So I'm piggybacking on Masa's message to ask the community for clarification.

Best,
Hanna

和田真孝 via eeglablist <eeglablist at sccn.ucsd.edu> ezt írta (időpont: 2024.
okt. 6., Vas 3:22):

> Hi all,
>
> I usually use ASR for preprocessing in resting-state EEG analysis.
> This function removes segments of data that contain excessive noise.
> It works quite well; however, after the rejection, it directly
> concatenates the periods before and after the removed segments,
> resulting in abrupt changes in the waveform. I am concerned that these
> abrupt changes may introduce additional noise, such as ripples, in
> subsequent steps of the analysis, such as time-frequency or connectivity analysis.
>
> Is this approach acceptable for further analysis? Or do you know of
> any good solutions to avoid this problem?
>
> Best,
> Masa
>
> --
> Masataka Wada
> Postdoctoral Scholar, Brain Stimulation Lab Department of Psychiatry
> and Behavioral Sciences Stanford University
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