[Eeglablist] search for spike

[Camilo José Borrego Abello]

Hi Arno and Jeff:

Thanks for your mail.You are quite right. The best is
to use menu Plot>component ERP>with scalp component
maps. The first component in the top line of the
window was found around the same location for the 3
epoch lenght used by dipfit.

 The current opinion ( Scherg, Ebersole group´s,
Lantz-see J. Clin. Neurophysiol. 20(5):311-319,2003)
is to work with the rise part of the spike. Certainly
Gotman group´S is not very clear at this matter. They
use segments lenght of 320 ms and 640 ms (see
Kobayashi et al, Clin. Neurophysiol. 112(2001):
405-413 page 407),or increasing the number of spikes,
the "density", minimizing the background of EEG
without success. In the last case they said that it
was because of the kurtosis is affected, as spikes
became small and not peaky, but this may not be true
because the kurtosis is in reality not affected, it is
just a scale adjustement in the printed drawing. 

That was the reason behind our question of the ideal
lenght for a good ICA decomposition in
epilepsy.Increasing the number of channels perhaps is
not the complete solution.

This is a warning for people who work on this area
with DIPFIT as it is possible to miss the right
location, until a reasonable length is found. The
ideal epoch length remain to be determined. 
 
Best regards,

Camilo Borrego
Universidad de Antioquia
Medellin, Colombia   

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