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

[Ramon]

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.kr>님이 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