[Eeglablist] Odd looking channel spectra

[Lea Lindemann]

Hi,

I'm new to EEGLAB and EEG and am trying to familiarize myself with the 
data processing tools.

When I visualize the spectra of my EEG channels with 'Plot > Channel 
spectra and maps' (default setting) the spectra look quite odd (see link 
below) although the EEG itself looks normal. It is plotted with 'Plot > 
Channel data (scroll)', 'Display > Remove DC offset' = on. What could be 
the reason for this?

I use EEGLAB v8.0.3.5b with Matlab 7.1.b The data were acquired using 
the BioSemi ActiveTwo system with 32 electrodes on the head + 4 
electrodes EOG and average mastoids as reference.

EEG:
ftp://europa.cg.cs.tu-bs.de/pub/public/people/lindemann/eeg.png

Spectra:
ftp://europa.cg.cs.tu-bs.de/pub/public/people/lindemann/spectrum.png

Best regards,
Lea