[Eeglablist] filter problems

[Nathan Weisz]

Hi all,

we've encountered some problems during filtering.
Data: MEG (SR 678.17; .1-200 Hz); 10 times auditory stimulation

In eeglab we filterd the raw data 1-20 Hz bandpass (eeglab 4.512 &  
4.515 in Matlab 6.5 & Matlab 7.04). However when looking at the data  
we see simply a sinusoidal modulation at 22 Hz.
When we first filter with high-pass then low-pass, no problem & the  
data incl. topographies look sensible (auditory N1m). I'm not sure  
why this happens (we frequently repeated the procedure).
Found some filter problems described here:
http://sccn.ucsd.edu/eeglab/Known_bugs.html

but it's not quite the same as what we see now.

Best,
Nathan


--------------------------------
Dr. Nathan Weisz
Dept. of Psychology
University of Konstanz
P.O. Box D25
78457 Konstanz, Germany

Tel: ++49-7531-884612
Email & Chat-AV: nathanweisz at mac.com
Homepage: http://homepage.mac.com/nathanweisz