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

[노태곤]

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
>
>
>