[Eeglablist] Consequences of manual rejection on continuous data

[Bryan Hall]

Hello Alexis,

Can you provide a little more information about your method and analysis?

1. You have 4 minute blocks…what is the resolution of a segment? Are the noisy segments within the 4 minute block?
2. When you remove noisy segments and then “cut and splice” is this within a 4 minute block?
3. What resolution are you targeting for power spectrum analysis?
4. What does your power spectrum analysis process look like in detail? Even band pass filters can add artifacts around edges.

The short answer is that I think you are definitely adding noise with “cut and splice” but it may not cause you an issue depending on what and how you are doing your analysis. One way to largely avoid this issue to calculate PSD for each continuous segment (cut) and don’t splice. Instead recombine the PSD for each segment back into a single answer for your 4 minute block.

There are much smarter EEG minds here than me however so take my advice with a grain of salt.

Talk to you soon,

Bryan

> On Feb 3, 2025, at 3:23 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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