Dear Rik, dear Karsten,
thank you for your replies.
I used global scaling and the adjusted data actually show a decrease of
activation, that reflects a negative hrf.
The betas of the temporal derivatives are not very high and a fourier
set analysis models a negative hrf that resembles that of SPM.
Also, as mentioned in my first mail, the contrast images display
significant activation differences in areas, that make sense in the
context of the experiment (in some areas also with high and low positive
betas).
Are there any other ideas on this topic. I am sure many people must have
encountered this finding.
Thank you for any other suggestions.
Frank
--
Dr. med Frank Jessen
Klinik für Psychiatrie und Psychotherapie
Universität Bonn
Sigmund-Freud-Str. 25
53105 Bonn
Tel: 0228-287-5743
Fax: 0228-287-6097
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