Reply-To: | | [log in to unmask][log in to unmask]> wrote: >> >>> I could be wrong, Karl or Darren please correct me if I am. >>> >>> X0 is composed of the high-pass filter and constant term. Thus, you >>> want to filter these out of the Yc regressor. However, you don't want >>> to filter out anything related to neural activity, so you wouldn't >>> want to filter your signal and then predict the neural activity from >>> the filtered signal, especially filtering frequencies. >>> >>> 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 Sat, Apr 30, 2011 at 8:03 PM, Alex Fornito <[log in to unmask]> >>> wrote: >>>> Hi Donald, >>>> As far as I can tell, spm_regions filters and whitens the VOI time series, >>>> and adjusts for the null space of the contrast if an adjustment is >>>> specified >>>> in xY.Ic. It defines the confound matrix, X0, but does not correct for it. >>>> The following line in spm_peb_ppi corrects for the confounds. >>>> >>>> Yc = Y - X0*inv(X0'*X0)*X0'*Y; >>>> PPI.Y = Yc(:,1); >>>> >>>> So the above correction does seem to be doing something different to >>>> spm_regions. I'm wondering why the uncorrected data, Y, is used when >>>> generating the ppi interaction term, while the corrected data Yc is to be >>>> used as a covariate of no interest in the PPI model. I would has thought >>>> that Yc should be used to generate the ppi interaction term as well. >>>> >>>> In my data, my X0 is a 195 x 7 matrix (I have 195 volumes per session). >>>> >>>> Regards, >>>> Alex >>>> >>>> >>>> On 30/04/2011 02:22, "MCLAREN, Donald" <[log in to unmask]> wrote: >>>> >>>>>thêQ |