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The contrast: (speech>baseline_post) > (speech>baseline_pre) will test for any increases in the contrast for post>pre. If (speech>baseline_pre) is significant, then you could still find a significant effect with the above contrast. The contrast does not test for activation in ONLY one contrast. I think you need to decide what you want to test, before trying different combinations: (1) Do you want only regions that are significantly different and not active at pre? (2) Do you want regions that might not be different pre/post, but only active at post? (3) Do you want only regions that are significantly different and active at post? (4) Do you want only regions that are significantly different, active at post, but not active at pre? Once you decide exactly what you want to test, then deciding which contrasts are needed will become easier. 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 Mon, Jul 14, 2014 at 6:03 PM, Pilar Archila-Suerte < [log in to unmask]> wrote: > Thank you. That's exactly what I have. I have both sessions modeled in the > same script per subject and I have an explicit baseline. > > How would you do a contrast like ... > (speech>baseline_post) > (speech>baseline_pre) > > ...to see only the activity in post-scan in response to speech relative to > baseline AND relative to the pre-scan? > > What I've done so far is look at the activity of *speech>baseline_post* > masking out the voxels of the pre-scan (i.e., speech>baseline_pre). > > Would you do it differently? > > Pilar A. > > > On Sun, Jul 13, 2014 at 2:50 AM, MCLAREN, Donald <[log in to unmask] > > wrote: > >> You need to have both the pre- and post-training sessions in the same >> model. Then you create two contrasts: (1) speech>baseline in pre-training; >> and (2) speech>baseline in post-training. >> >> If baseline is just the implicit baseline, then your contrasts >> speech>baseline are just speech>0. >> >> If the two time-points are in different model, then you can subtract the >> two contrasts to get the difference, which is what your example was >> investigating. >> >> -Donald >> >> >> On Fri, Jul 11, 2014 at 7:19 PM, Pilar Archila-Suerte < >> [log in to unmask]> wrote: >> >>> >>> Dear SPM Users: >>> How could I sensibly create a complex contrast at the first level to >>> compare between task/ rest and before/after training scans? >>> Ex: (speech > baseline before training) > (speech>baseline after >>> training). >>> >>> I need to run another complex contrast at the second level (between >>> groups) so I'd like to run these two complex contrasts of task and time at >>> the first level. >>> >>> Any help would be greatly appreciated. >>> >>> Pilar A. >>> >> >> > > > -- > Pilar Archila, Ph.D > Postdoctoral Fellow > Laboratory for the Neural Bases of Bilingualism > Psychology Department > University of Houston > Primary e-mail address: [log in to unmask] > >