The duration of the response is what you expect the neural activity to be for the process you are trying to capture -- not necessarily the duration of the stimulus. For example, if I do a visual search task and I find the target after 1s, but the stimulus is on for 5 seconds; then I'd want to model the visual search for 1s and potentially model the visual stimuli for 5s. Thus, you really need to think about the cognitive processes and the neural activity associated with them when you choose a event duration. In your case, I'd look at the fear literature to see if the fear response is constant or is mostly at the beginning of the stimuli to guide you. Hope this helps. Best Regards, Donald McLaren ================= D.G. McLaren, Ph.D. Postdoctoral Research Fellow, GRECC, Bedford VA Research Fellow, Department of Neurology, Massachusetts General Hospital and Harvard Medical School 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 Sun, Nov 27, 2011 at 3:13 PM, adams adams <[log in to unmask]> wrote: > Hello SPMers > > > Im studying fear circuit ( conditioning and extinction) > > The Duration of the stimulus is 6s : consist of face stimulus (3s) > followed by the rating response (3s) > > ( during the rating response the stimulus is still presented) > > > > My question is : in the FMRI Model specification what is the duration of > my condition. Do I have to enter : 3s or 6s, or 0 > > > Thank you for your help > > > Adams > > > >