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If you want to "ignore the entire time window" cut out that time window - otherwise you are including it in the model. NaNs will break the design matrix math. 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 Wed, Jul 31, 2013 at 6:52 PM, Jason Ozubko <[log in to unmask]> wrote: > This is a question for the 1st level fMRI specification step. > > I'm trying to include some regressors into my design matrix to look for > brain areas that modulate with certain ongoing measures. At the start of > each session, there is 30-60s where subjects are doing a different task and > so we have no ongoing measures for the primary task (i.e., they haven't yet > started the primary task). I don't want to trim away the first 30-60s of > each session because there are important trial types in that period that I > am analyzing. > > So, is it possible to include regressors where SPM ignores the first 30-60s > of those regressors? I thought that perhaps having NaN values for the > regressors during the first 30-60s would lead SPM to ignore that time window > but I don't know the inner workings of SPM enough to be certain it would > work. Does anyone know if it would indeed work, or if there are any other > ways to get SPM to ignore a regressor during certain time windows? > > Thanks in advance > > Cheers, > Jason