Dear Alfonso

Thanks for your reply!
But even if I change the threshold to say 10% (see attached) there is no change in signal explained throughout the brain (which is strangely the case for some but not all subjects). I checked also the firstlevel results as you suggested; for these subjects I'll find no connectivity even for very liberal thresholds- again for the whole brain (see attached).
 
But the picture changes if  I change the settings from implicit- to brain-mask,  (see attached the BOLD-signal explained for the same subject with this procedure). Could you please comment on this?
Best
Diana