[Eeglablist] Pronounced Occipital-Dominant Activity in Brain Products EEG Recordings

[Cedric Cannard]

Hi Tae-Gon,

Could it be a different referencing method during recording?


Cedric



On Wednesday, August 20th, 2025 at 1:05 PM, Ramon via eeglablist <eeglablist at sccn.ucsd.edu> wrote:

> Hi Tae-Gon, I forwarded your email to the Brain Products technical Support
> Team (techsup at brainproducts.com). They may contact you soon.
> Cheers,
> R
>
> On Fri, Aug 15, 2025 at 8:43 AM 노태곤 via eeglablist eeglablist at sccn.ucsd.edu
>
> wrote:
>
> > Hi everyone,
> > We have been seeing a strange and persistent pattern in our EEG recordings
> > and would like to hear if anyone has experienced something similar.
> >
> > Setup:
> > - Brain Products actiCAP + BrainAmp amplifier
> > - Multiple cap sizes, matched to head size & sex
> > - Participants: asian adults (Both Healthy and disease model)
> > - Low impedances, controlled environment Previous system (Grass/Natus +
> > Waveguard Cap, ANT)
> > - resting EEG (eye-closed)
> > did not show this issue. Across all participants and experiments, we
> > observe occipital-dominant activity in the topography, regardless of
> > frequency bands.
> > It appears consistently even with different caps, operators, and recording
> > days.
> >
> > While similar occipital activity can be seen in the high-frequency range
> > with our previous Grass system, it is far less pronounced compared to the
> > Brain Products recordings.
> >
> > What we’ve checked Environmental artifacts → unlikely (appears in all
> > subjects)
> > Alpha–beta misclassification → no change in alpha topography when redefined
> > Population-specific head shape → possible, but Waveguard data from same
> > population was normal
> > Multiple preprocessing pipelines → same result
> >
> > I’d like to know: Has anyone observed a similar occipital-dominant pattern
> > with Brain Products systems? Any insights on possible causes (hardware,
> > grounding, reference) or troubleshooting steps would be greatly
> > appreciated.
> >
> > I cannot attach the photos due to file size limitations, so I have uploaded
> > them to Google Drive. If anyone knows a possible solution, I would greatly
> > appreciate your help.
> >
> > https://urldefense.com/v3/__https://docs.google.com/presentation/d/1yNdbF19b0yeZgJkZrqkh4hBKim9NWYmxkfOo_TbrF6c/edit?usp=sharing__;!!Mih3wA!DqD6hmELArRDl9iR-iffsn3x_Kul-6lwaWCJjZc09V-i-01zJvm2iIefFQ9g05HOVDdaWCfA63RJ1giU4QqXzJaC$
> >
> > Thanks,
> > Tae-Gon
> >
> > 2025년 8월 14일 (목) 오후 10:32, 노태곤 ghgh3110 at snu.ac.kr님이 작성:
> >
> > > Hi everyone,
> > > We have been seeing a strange and persistent pattern in our EEG
> > > recordings
> > > and would like to hear if anyone has experienced something similar.
> > >
> > > Setup:
> > > - Brain Products actiCAP + BrainAmp amplifier
> > > - Multiple cap sizes, matched to head size & sex
> > > - Participants: asian adults (Both Healthy and disease model)
> > > - Low impedances, controlled environment Previous system (Grass/Natus +
> > > Waveguard Cap, ANT)
> > > - resting EEG (eye-closed)
> > > did not show this issue. Across all participants and experiments, we
> > > observe occipital-dominant activity in the topography, regardless of
> > > frequency bands.
> > > It appears consistently even with different caps, operators, and
> > > recording
> > > days.
> > > [image: image.png]
> > > (an example of a patient, but healthy participants also showed same
> > > patterns)
> > >
> > > While similar occipital activity can be seen in the high-frequency range
> > > with our previous Grass system, it is far less pronounced compared to the
> > > Brain Products recordings.
> > >
> > > [image: image.png]
> > > (Grass system, a patient case in the same cohort)
> > >
> > > What we’ve checked Environmental artifacts → unlikely (appears in all
> > > subjects)
> > > Alpha–beta misclassification → no change in alpha topography when
> > > redefined
> > > Population-specific head shape → possible, but Waveguard data from same
> > > population was normal
> > > Multiple preprocessing pipelines → same result
> > >
> > > I’d like to know: Has anyone observed a similar occipital-dominant
> > > pattern
> > > with Brain Products systems? Any insights on possible causes (hardware,
> > > grounding, reference) or troubleshooting steps would be greatly
> > > appreciated.
> > >
> > > Thanks,
> > > Tae-Gon
> >
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>
>
>
>
> --
> _____________________________________________________
> Ramon Martinez-Cancino, PhD
> _______________________________________________
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