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Hi Steve Thank you for your reply. I'm actually about to attend the FSL course end of May but I wanted to try analyzing a couple of subjects fMRI data prior to coming. You have helped me with my previous question, however Im still undecided about how to set up my model. I do have 3 EVs (A, B, C) but they are also repeated within the same session ie A B C C B A. How can I let FEAT know that? Also, all my conditions have identical durations so how do I make them different? Unless I'm supposed to alter the 'phase' to reflect that? Many thanks for your help. Cheers Reem On 3/05/2010, at 19:06, "Stephen Smith" <[log in to unmask]> wrote: > Hi - from the sounds of it you setup all 3 EVs to be identical. This > is why you get this error message. > Cheers. > > > On 3 May 2010, at 07:35, Reem Jan wrote: > >> Hello FSL users >> >> Can someone please help me with this error message: >> Problem with processing the model: Warning: at least one EV is (close >> to) a linear combination of the others. You probably need to alter >> your >> design. (Design matrix is rank deficient - ratio of min:max >> eigenvalues >> is SVD of matrix is 8.88555e-34) >> >> I got this error message when I tried to View Design after setting >> up my >> model of 3 EVs, for each EV I entered the following values: >> Off = 16, On = 40, Phase = 16. I chose a square basic shape and left >> convolution as it is in the default settings (Gamma). Where did I go >> wrong? >> >> Many thanks in advance for your help. >> >> Kind regards >> Reem >> >> On Wed, 2010-03-31 at 19:11 +0100, Stephen Smith wrote: >>> Hi >>> >>> On 29 Mar 2010, at 02:18, Reem Jan wrote: >>> >>>> Dear FSL experts >>>> >>>> I am a brand new FSL user. I run a blocked Stroop task with fMRI, >>>> and I >>>> have previously analysed some of my data using SPM. I am trying to >>>> learn >>>> using FEAT and unfortunately I'm getting stuck at very preliminary >>>> stages.. Can someone please help? >>>> I'll explain my paradigm and what I have been entering in the GUI >>>> so >>>> far.. >>>> >>>> My TR is 3 seconds >>>> I have 118 functional images per subject. >>>> The blocked Stroop task I use is set up as follows: >>>> Rest (16sec) - Neutral condition (40sec) - Rest (16sec) - Congruent >>>> condition (40sec) - Rest (16sec) - Incongruent condition (40sec) - >>>> Rest >>>> (16sec) - Incongruent condition (40sec) - Congruent condition >>>> (40sec) - >>>> Rest (16sec) - Neutral condition (40sec) >>>> >>>> I have several questions: >>>> 1) Does that make my design rA-rB-rC-rC-rB-rA? >>>> >>> >>> >>> Yes; you won't explicitly model the rest conditions - you will have >>> EV1=A EV2=B EV3=C >>> >>>> >>>> 2) Is my 'high pass filter cutoff' = r+A+r+B+r+C >>>> (16+40+16+40+16+40) >>>> = >>>> 168sec? >>>> >>> >>> >>> It depends on your contrasts - have a read of the Smith NeuroImage >>> paper on efficiency, and a play with the efficiency estimator in >>> FEAT. >>> >>>> 3) My data is acquired with interleaved order but for a blocked >>>> design >>>> like mine, do I need to use slice time correction? (I know I don't >>>> tick >>>> that option in SPM). >>>> >>> >>> >>> No, we generally recommend against that. >>> >>>> 4) I struggled with setting up a full model despite reading the >>>> instructions on FSL webpage. According to the information I >>>> supplied >>>> above, do I have 3 or 6 EVs? as I have a repetition of each >>>> condition as >>>> described above. >>>> >>> >>> >>> You have 3 "original" EVs, which by default will get turned into 6 >>> "real" EVs once the temporal derivatives are added by FEAT for you. >>> >>> >>> Cheers. >>> >>> >>> >>> >>> >>>> >>>> I greatly appreciate your time and advice. >>>> >>>> Kind regards >>>> Reem >>>> >>>> >>> >>> >>> --- >>> --- >>> --- >>> ------------------------------------------------------------------ >>> Stephen M. Smith, Professor of Biomedical Engineering >>> Associate Director, Oxford University FMRIB Centre >>> >>> FMRIB, JR Hospital, Headington, Oxford OX3 9DU, UK >>> +44 (0) 1865 222726 (fax 222717) >>> [log in to unmask] http://www.fmrib.ox.ac.uk/~steve >>> --- >>> --- >>> --- >>> ------------------------------------------------------------------ >>> >>> >>> >>> >>> >>> >>> >> > > > --- > --- > --------------------------------------------------------------------- > Stephen M. Smith, Professor of Biomedical Engineering > Associate Director, Oxford University FMRIB Centre > > FMRIB, JR Hospital, Headington, Oxford OX3 9DU, UK > +44 (0) 1865 222726 (fax 222717) > [log in to unmask] http://www.fmrib.ox.ac.uk/~steve > --- > --- > --------------------------------------------------------------------- > > >