[Eeglablist] Consequences of manual rejection on continuous data

[Scott Makeig]

Also, Alexis -

The *EEG.urevent* field contains the marked times and types of ALL the
original dataset event markers, in case your analysis needs to use this
info to inform analysis of the remaining 'good' data after data rejection.

Scott

On Tue, Feb 11, 2025 at 4:26 PM Makoto Miyakoshi via eeglablist <
eeglablist at sccn.ucsd.edu> wrote:

> Hi Alexis,
>
> For the effect of spurious time-frequency modulations by the 'boundaries'
> (i.e. time-domain data splicing), see this lecture from this time window.
>
> https://urldefense.com/v3/__https://youtu.be/NHKIPU_T7-0?t=1861__;!!Mih3wA!BvbL3M2FKPfr96zDK2dQozcuEb3JkI1D0L68Em1CBkp9fdEZQmMUs2hdY1aatbXEZd9JhVC7dsPXleIwBuZ5zduV4as$
>
> That said, at least within EEGLAB, 'boundary' event markers are treated
> with special care by filter functions so that sub-windows containing the
> 'boundary' are excluded from the process.
> So, spurious artifacts in the frequency domain should not appear.
>
> However, when you export your data to other applications without the
> 'boundary' event markers, you may experience troubles when applying
> frequency filters (thanks Masataka for pointing this out!)
>
> Makoto
>
> On Tue, Feb 4, 2025 at 12:47 PM Alexis Leiva via eeglablist <
> eeglablist at sccn.ucsd.edu> wrote:
>
> > Dear all,
> >
> >  I am performing an experiment with 4-minute blocks to analyze the power
> > spectrum from the entire block but not in epochs. Then, when I manually
> > reject a noisy segment from the continuous data in EEGLAB, a boundary
> mark
> > event appears in the channel data.
> >
> > Now, my question: Is this method of rejection and the boundary mark
> > apparition in EEGLAB a “cut and splice” implementation, inserting a kind
> of
> > imbalance into the signal after splicing the pre- and post-noise
> segments?
> > Knowing the possible consequences of manual rejection of my continuous
> data
> > is critical because I don’t know if this implementation might cause a
> > non-evident discontinuity of my data, some distortion, unreliable
> outcomes,
> > or another kind of issue on the power spectrum calculus through Welch’s
> > method on the entire blocks.
> >
> > I appreciate your help.
> >
> > Regards,
> >
> > Alexis
> >
> > --
> >  Alexis Leiva Catalán
> > Tecnólogo Médico  mención en ORL Universidad de Chile.
> >  Candidato a PhD Neurociencias Pontificia Universidad Católica De Chile.
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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