Hi, peter
I'm sorry for the continuous post on the message board, and thank you very much for your patience and help, I might have found out why the ventricle is lit up.
I think the cause of the bright ventricle is that the story time points include the fixation time before the audio was played(8TR fixation time before each story).
The ventricles looks normal when I did the correlation in pure story time points in my 10 subjects(a screenshot is attached). It may be ... that the machine's initial signal is unstable before a new run...,I guess.
best,
Dan