I can think of two approaches:
(1) Turn off the high-pass filter because the mood induction occurs during scanning.
(2) Do the mood induction before scanning the task, this way you have a steady state of the altered mood.

Best Regards, Donald McLaren
=================
D.G. McLaren, Ph.D.
Research Fellow, Department of Neurology, Massachusetts General Hospital and
Harvard Medical School
Postdoctoral Research Fellow, GRECC, Bedford VA
Website: http://www.martinos.org/~mclaren
Office: (773) 406-2464
=====================
This e-mail contains CONFIDENTIAL INFORMATION which may contain PROTECTED
HEALTHCARE INFORMATION and may also be LEGALLY PRIVILEGED and which is
intended only for the use of the individual or entity named above. If the
reader of the e-mail is not the intended recipient or the employee or agent
responsible for delivering it to the intended recipient, you are hereby
notified that you are in possession of confidential and privileged
information. Any unauthorized use, disclosure, copying or the taking of any
action in reliance on the contents of this information is strictly
prohibited and may be unlawful. If you have received this e-mail
unintentionally, please immediately notify the sender via telephone at (773)
406-2464 or email.


On Thu, Jul 24, 2014 at 6:38 PM, Stefania Ashby <[log in to unmask]> wrote:
Dear SPM Experts,

I am currently working on designing a task and I am concerned that when we reach the preprocessing step our high-pass filter will filter out the signal from our condition of interest causing us to lose power.

Our task consists of 6 scanner runs. Trial types are the same across all runs; however, 3 of our runs will have a mood-induction component while the other 3 runs do not. Within each of these runs we have further broken down the trials into 6 “mini blocks”, meaning we present trials (all trials are jittered) in 6 blocks of approximately 45 sec for each block, with a 10 second rest between each “mini blocks”, for a total of 330 sec per run. These runs will be randomized and counterbalanced across participants.

We are worried that the runs containing the sustained mood effect, will have that effect over the course of the run.  Since the effect will have a duration greater then that of the standard high-pass filter window,  will that filtering cause us to lose power?

Are our concerns about the high-pass filter valid and do you have any suggestions on how we could design our task and still give the mood we are trying to induce time to build up? Any comments or suggestions are welcomed.

Thank you!

Stefania