[Eeglablist] channel spectra and maps

[pickard at telusplanet.net]

I performed the channel spectra and maps for a 500 ms epoch in two data 
conditions.  Two questions:

1.  I checked "both" for both EEG and ERP.  However, I was expecting some 
indication of the time/peak chosen for the ERP. The ERP and EEG maps for the 
500 ms epoch were quite different.  Is the ERP map indicating the spectra/map 
at the largest peak (but not providing info about when) or is it providing some 
other information? Can the ERP portion only be completed on extremely short 
epochs so that the user can be reasonably certain which peak is being modelled?

2.  If memory serves me, the maps use an arbitrary scale for the colors/color 
intensity.  (I've been trying to locate where I read that but I haven't had any 
luck.)  So ... dumb question for the day - if I have maps for the same 
individual but different conditions, does this mean that I cannot visually 
compare the intensity of the colors of the maps as each may have a different 
arbitrary scale?  Similarly, I would not be able to visually compare across 
subjects?  Is there anyway to standardize the scale?

Thanks for your help, 

Patti Sorensen,
PhD Candidate
University of Lethbridge