Re: [Freesurfer] [martinos-tech] parametric modulation

For condition 4 (posslope), the weight is always 0. You can't compute a slope if all the values are the same. doug

On 10/29/2013 10:44 AM, Suzanne Oosterwijk wrote:

Hi Doug,

Attached is the Xtmp.mat file for the analysis that gets the error.

Thanks for your response on the second question. I am not sure what you mean with demeaning, so I guess that I am not doing that :-) I just wanted to make sure that not getting the same results does not indicate a fundamental problem in my paradigm files.

Thanks! Suzanne

On Tue, Oct 29, 2013 at 3:31 PM, Douglas N Greve <greve@nmr.mgh.harvard.edu mailto:greve@nmr.mgh.harvard.edu> wrote:

Hi Suzanne, can you send me the Xtmp.mat file that gets created?

On your second question, the answer might be a little tricky.
First, are you demeaning the modulation value? If not, then you
can certainly get different maps. The other part is that you can
get unpredicatable results because the design matrix is not
orthogonalbecause you have several event types.

doug



On 10/28/2013 12:30 PM, Suzanne Oosterwijk wrote:

    Hi Doug,

    I am running parametric modulation analyses in which I am
    modeling 5 different ratings given by participants in response
    to images. To model these ratings I made paradigm files
    defining both the onset and the slope for each trial (see
    email exchange below). Since I have 5 different ratings, I
    made 5 different paradigm files per participant, per run.
    These paradigm files hold the exact same trial sequence, only
    with different numbers for the slope condition. When running
    selxavg3-sess I get the following error:

    Input to SVD must not contain NaN or Inf.

    Error in cond (line 36)
    s = svd(A);

    Error in fast_selxavg3 (line 279)
    XCond = cond(XtX);

    The strange thing is that selxavg3-sess stops running at a
    particular participant when I am trying to model one
    particular rating, whereas the exact same analysis for the
    other three ratings I have run so far (for the same
    participant) does not result in an error. I checked the
    paradigm files over and over but I cannot find the mistake.
    The paradigm files are all the same in terms of timing and
    condition codes etc., the only thing that is different between
    the files are the specific ratings per trial. So I really
    don't understand why I get this error. I attached the paradigm
    files for the erroneous analysis and also for the analysis
    that runs successfully. I also attached the selxavg3-sess
    logfile for the an erroneous analysis and for the successful
    one. Maybe I am missing something here, but I just don't see it.

    Also, I have one other question concerning the parametric
    modulation. As I understand it modeling the onset is the same
    analysis as a normal contrast comparing a particular condition
    against baseline. I compared the onset significance maps
    (comparing onset to baseline) for each separate rating, and to
    my surprise they are not the same. Since only the ratings
    differ between the different analyses, and not the onset times
    of the stimuli, I expected those maps to be completely
    identical. Am I right in this assumption, or is there a reason
    they can be different?

    Thanks!
    Suzanne



    On Thu, Aug 15, 2013 at 4:28 PM, Douglas Greve
    <greve@nmr.mgh.harvard.edu <mailto:greve@nmr.mgh.harvard.edu>
    <mailto:greve@nmr.mgh.harvard.edu
    <mailto:greve@nmr.mgh.harvard.edu>>> wrote:

        Hi Suzanne, that is fine
        doug



        On 8/14/13 7:13 AM, Suzanne Oosterwijk wrote:

            Hi Doug,

            Just a follow-up question. The ratings that I
        collected for the
            parametric modulation analysis have a range from 0 to
        1. This
            means that the weights for some stimuli will have the
        value 0. Is
            this a problem? I am asking just to make sure that a
        weight of 0
            does not exclude the corresponding data-point.

            Thanks,
            Suzanne


            On Fri, Jul 26, 2013 at 7:14 PM, Douglas Greve
            <greve@nmr.mgh.harvard.edu
        <mailto:greve@nmr.mgh.harvard.edu>
        <mailto:greve@nmr.mgh.harvard.edu
        <mailto:greve@nmr.mgh.harvard.edu>>> wrote:

                Hi Suzanne, yes that looks correct.
                doug



                On 7/26/13 9:27 AM, Suzanne Oosterwijk wrote:

                    Hello all,

                    I want to perform a parametric modulation
            analysis in
                    Freesurfer and I have a question about how to
            adapt my
                    paradigm file. I understand how to code the
            offset and the
                    slope (by adding the individual ratings as the
            slope
                    weight), but I just want to check whether I am
            correctly
                    modelling the trials of no interest.

                    I have presented people with negative,
            positive and neutral
                    images all preceded by a fixation cross. I
            have individual
                    ratings for the negative images that I want to
            use for the
                    parametric modulation analysis, but I don't
            have any ratings
                    for the positive and neutral images. I do want
            to model
                    these images and the fixation cross, however,
            to make sure
                    that do not become part of the null. Based on
            the wiki I
                    adapted my paradigm file like this:

                    (1 = offset for the negative image; 2 = slope
            for the
                    negative image; 3 = neu/pos image of no
            interest; 4 = fixation)

                    00121NULL
                    12431fix
                    15131negoffset
                    1523.79negslope
                    18431fix
                    21331neu/pos
                    24431fix
                    27131negoffset
                    27231.00negslope
                    30431fix
                    33131negoffset
                    3323.49negslope
                    36091NULL
                    etc.

                    Is this correct?

                    Thanks so much for responding!
                    Suzanne



                    --
                    Suzanne Oosterwijk, Ph.D.

                    Postdoctoral Researcher

                    Department of Social Psychology

                    University of Amsterdam

                    s.oosterwijk@u <mailto:s.oosterwijk@neu.edu
            <mailto:s.oosterwijk@neu.edu>>va.nl <http://va.nl>
            <http://va.nl>


            https://sites.google.com/site/suzanneoosterwijk/

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            --
            Suzanne Oosterwijk, Ph.D.

            Postdoctoral Researcher

            Department of Social Psychology

            University of Amsterdam

            s.oosterwijk@u <mailto:s.oosterwijk@neu.edu
        <mailto:s.oosterwijk@neu.edu>>va.nl <http://va.nl>
        <http://va.nl>

        https://sites.google.com/site/suzanneoosterwijk/





    -- 

    Suzanne Oosterwijk, Ph.D.

    Postdoctoral Researcher

    Department of Social Psychology

    University of Amsterdam

    s.oosterwijk@u <mailto:s.oosterwijk@neu.edu
    <mailto:s.oosterwijk@neu.edu>>va.nl <http://va.nl> <http://va.nl>

    https://sites.google.com/site/suzanneoosterwijk/


-- 
Douglas N. Greve, Ph.D.
MGH-NMR Center
greve@nmr.mgh.harvard.edu <mailto:greve@nmr.mgh.harvard.edu>
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--

Suzanne Oosterwijk, Ph.D.

Postdoctoral Researcher

Department of Social Psychology

University of Amsterdam

s.oosterwijk@u mailto:s.oosterwijk@neu.eduva.nl http://va.nl

https://sites.google.com/site/suzanneoosterwijk/