Thanks for that Doug!

Cheers,


*Dr Kevin Aquino*
Research fellow,
Sir Peter Mansfield Magnetic Resonance Center, The University of
Nottingham.

Honorary Research Fellow
School of Physics, Faculty of Science, University of Sydney

*E* [email protected], [email protected] | *W*
https://kevinaquino.github.io <http://www.physics.usyd.edu.au/~aquino/>

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On Fri, Aug 18, 2017 at 7:28 AM, Douglas N Greve <[email protected]>
wrote:

> selxavg uses scenario #1, which corresponds to the 2nd image below, ie,
> all the task regressors are in a single column and not pulled out on a
> run-by-run basis. The nuisance regressors are specific to each run.
>
>
> >
>
> On 08/16/2017 08:24 PM, Kevin Aquino wrote:
> > Thanks for that Doug,
> >
> > [I was hoping i could do the parametric modulation in the contrast
> > weights -- SPM style of doing this after the betas were fit].
> >
> > Regarding the X.mat question, sorry I wasn't clear. I can see it has
> > the nuisance regressors and constant terms, but is that x.mat used to
> > estimate the betas?
> Yes
> >
> > In the beta estimation which scenario is happening?
> >
> > 1. concatenate all the model regressors onto one column, add the
> > nuisance regressors and constant terms into one big matrix (X.mat) to
> > estimate the beta values
> > 2. create a matrix for each run separately and estimate the betas.
> > Save regression coefficients, compute contrasts and significances of
> > contrasts. The end (default) result is the average (i guess average of
> > all the estimated quantities).
> >
> > From the help message it looks like it is #2, and if thats the case
> > then X.mat looks like its a summary. I ask this because I would like
> > to use a X that looks something like below:
> > Inline image 1,
> >
> > which is essentially the scenario in #2, but the output of X.mat looks
> > like this:
> >
> > Inline image 2
> > (the image hasn't been normalized so that is why there are blank
> > spaces for 3 of the 6 nuisance regressors)
> >
> > There are slight differences between the two (so it doesn't matter in
> > the long run) but I just want to know which one is being used. On a
> > quick look of selxag3-sess, the matlab files look like compiled mex
> > files, so I can't access them.
>
> >
> > Thanks!
> >
> >
> > *Dr Kevin Aquino*
> > Research fellow,
> > Sir Peter Mansfield Magnetic Resonance Center, The University of
> > Nottingham.
> >
> > Honorary Research Fellow
> > School of Physics, Faculty of Science, University of Sydney
> >
> >
> > ----------------------------------------------
> >
> > The brain is a wonderful organ. It starts working the moment you get
> > up and does not stop until you get into the office.
> > -
> > Robert Frost
> >
> > CRICOS 00026A
> > This email plus any attachments to it are confidential. Any
> > unauthorised use is strictly prohibited. If you receive this email in
> > error, please delete it and any attachments.
> >
> > Please think of our environment and only print this e-mail if necessary.
> >
> >
> > On Thu, Aug 17, 2017 at 8:24 AM, Douglas N Greve
> > <[email protected] <mailto:[email protected]>> wrote:
> >
> >     It has the design matrix plus a lot of other stuff in it. For
> >     parametric
> >     modulation, have you seen this page
> >
> >     https://surfer.nmr.mgh.harvard.edu/fswiki/FsFastParametricModulation
> >     <https://surfer.nmr.mgh.harvard.edu/fswiki/
> FsFastParametricModulation>
> >
> >     On 08/15/2017 09:52 PM, Kevin Aquino wrote:
> >     > Dear all,
> >     >
> >     > I have a question regarding the output from selxavg3-sess. I
> noticed
> >     > that within an analysis there  is a X.mat that looks like a design
> >     > matrix -- however is this used at any stage of the analysis?
> >     The help
> >     > message in selxavg3-sess reads:
> >     >
> >     > "This program will construct the design matrix for each run, fit
> >     > the GLM, save regression coefficients, compute contrasts and
> >     > significances of contrasts. The runs are combined together so the
> >     > output is the average across runs (some would call this a
> >     > "second-level" analysis)."
> >     >
> >     > so this looks like that x.mat is constructed and used for each run
> >     > (and not saved by default). This then looks like X.mat is not
> >     used in
> >     > the analysis -- it is just there for illustrative purposes? or
> >     have I
> >     > misinterpreted the help message.
> >     >
> >     >
> >     > If this is correct (i.e. X.mat in the output is not used) when
> >     making
> >     > contrasts using mkcontrast-sess, is there a way to parametrically
> >     > modulate each run? e.g. to model behavioural changes per run etc.
> >     >
> >     > Cheers,
> >     >
> >     >
> >     > *Dr Kevin Aquino*
> >     > Research fellow,
> >     > Sir Peter Mansfield Magnetic Resonance Center, The University of
> >     > Nottingham.
> >     >
> >     > Honorary Research Fellow
> >     > School of Physics, Faculty of Science, University of Sydney
> >     >
> >     > *E* [email protected]
> >     <mailto:[email protected]>
> >     > <mailto:[email protected]
> >     <mailto:[email protected]>>,
> >     [email protected] <mailto:[email protected]>
> >     > <mailto:[email protected]
> >     <mailto:[email protected]>> | *W* *MailScanner has
> detected a
> >     > possible fraud attempt from "www.physics.usyd.edu.au
> >     <http://www.physics.usyd.edu.au>" claiming to be*
> >     > https://kevinaquino.github.io
> >     <http://www.physics.usyd.edu.au/%7Eaquino/
> >     <http://www.physics.usyd.edu.au/%7Eaquino/>>
> >     >
> >     > ----------------------------------------------
> >     >
> >     > The brain is a wonderful organ. It starts working the moment you
> get
> >     > up and does not stop until you get into the office.
> >     > -
> >     > Robert Frost
> >     >
> >     > CRICOS 00026A
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> >     --
> >     Douglas N. Greve, Ph.D.
> >     MGH-NMR Center
> >     [email protected] <mailto:[email protected]>
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> --
> Douglas N. Greve, Ph.D.
> MGH-NMR Center
> [email protected]
> Phone Number: 617-724-2358
> Fax: 617-726-7422
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